http://www.citydeepsky.com/wiki/api.php?action=feedcontributions&user=Evilscientist&feedformat=atomCityDeepSky - User contributions [en]2024-03-29T05:19:24ZUser contributionsMediaWiki 1.19.17http://www.citydeepsky.com/wiki/index.php/Celestial_sphereCelestial sphere2022-05-19T13:29:04Z<p>Evilscientist: Add category</p>
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<div>[[Image:Celestial_sphere.png|right|thumb|200px|The Celestial Sphere]]<br />
The celestial sphere is an imaginary sphere around the [[Earth]] in which the objects in the sky appear fixed to. If you look at the night sky, it does look somewhat like a bowl or half sphere over the ground. This appearance gave ancient astronomers the idea that a sphere surrounded the Earth and that the [[star|stars]] were fixed to this sphere, which then rotated around the Earth. The [[Sun]], [[Moon]], and [[planet|planets]] were then thought to move against the celestial sphere around the Earth in their own orbits.<br />
<br />
Now in modern times we know that there isn't a sphere around the Earth in which the stars are fixed. The stars are all at different distances from the Earth and the ones we can see with the unaided eye are all in our Galaxy and don't rotate around the Earth, but orbit the centre of our Galaxy. That being said it is often useful to think of the sky as a sphere around the Earth for the convenience of mapping and observing.<br />
<br />
==Parts of the Celestial Sphere==<br />
<br />
There are parts of the celestial sphere that are useful to know when talking about where things are in the night sky or defining the various coordinate systems used to locate objects in the sky.<br />
<br />
=== Celestial Equator and Celestial Poles ===<br />
[[Image:Pole_equator.png|right|thumb|200px|The Celestial Equator and Poles]]<br />
If you project the Earth's equator onto the night sky you produce an imaginary line across the sky known as the celestial equator. This means that if you were standing on the Earth's equator looking due east, the celestial equator would start at the horizon, go straight up overhead and then down due west directly behind you. The height above the ground the celestial equator appears depends on how close you are (in [[latitude]]) to the Earth's equator. As with the terrestrial equator on the ground, the celestial equator divides the sky into northern and southern hemispheres.<br />
<br />
If you project the Earth's geographic/terrestrial [[Earth's poles|pole]] out onto the celestial sphere, you would then create the north and south celestial poles. Thus if you were to stand on one of the Earth's poles the and looked straight up you would be looking in the direction of one of the celestial poles (north if you were standing on the Earth's north pole, south if you were standing on the south pole). As with the celestial equator the height of the celestial pole depends on your latitude. In fact the height above the northern horizon of the north celestial pole is your latitude (change to the southern pole and horizon for south of the terrestrial equator).<br />
<br />
[[Category:Astronomical concept]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Alt_az.pngFile:Alt az.png2022-05-19T13:27:36Z<p>Evilscientist: Alt-az graphic {{evilcopy}}</p>
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<div>Alt-az graphic {{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Ra_dec.pngFile:Ra dec.png2022-05-19T13:26:55Z<p>Evilscientist: RA and dec together {{evilcopy}}</p>
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<div>RA and dec together {{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Right_ascension.pngFile:Right ascension.png2022-05-19T13:26:04Z<p>Evilscientist: Graphic showing measurement of RA {{evilcopy}}</p>
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<div>Graphic showing measurement of RA {{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Declination.pngFile:Declination.png2022-05-19T13:24:17Z<p>Evilscientist: Graphic for declination {{evilcopy}}</p>
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<div>Graphic for declination {{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Celestial_sphere.pngFile:Celestial sphere.png2022-05-19T13:23:34Z<p>Evilscientist: Evilscientist uploaded a new version of &quot;File:Celestial sphere.png&quot;: Reverted to version as of 08:04, 12 August 2015</p>
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<div>A graphic representing the celestial sphere about the Earth.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Celestial_sphere.pngFile:Celestial sphere.png2022-05-19T13:19:47Z<p>Evilscientist: Evilscientist uploaded a new version of &quot;File:Celestial sphere.png&quot;: Graphic to help describe the celestial sphere.</p>
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<div>A graphic representing the celestial sphere about the Earth.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Right_ascensionRight ascension2022-05-19T13:18:40Z<p>Evilscientist: </p>
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<div>Right ascension is a coordinate in the equatorial coordinate system. It is a measurement along the celestial equator measured in hours moving eastward from the first point of Aries, also known as the [[vernal equinox]]. It is analogous to the geographic coordinate of longitude. [[Declination]] is the other coordinate in the equatorial system.<br />
<br />
{{stub}}<br />
[[Category:Astronomical concept]]<br />
[[Category:Observing Concepts]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Right_ascensionRight ascension2022-05-19T13:18:23Z<p>Evilscientist: </p>
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<div>Right ascension is a coordinate in the equatorial coordinate system. It is a measurement along the celestial equator measured in hours moving eastward from the first point of Aries, also known as the [vernal equinox]. It is analogous to the geographic coordinate of longitude. [[Declination]] is the other coordinate in the equatorial system.<br />
<br />
{{stub}}<br />
[[Category:Astronomical concept]]<br />
[[Category:Observing Concepts]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Limiting_MagnitudeLimiting Magnitude2018-06-01T15:40:38Z<p>Evilscientist: /* Theoretical Limiting Magnitude */ add units for d</p>
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<div>Limiting magnitude is the [[magnitude]] of the dimmest object that can be seen with a particular optical system be it unaided eye's binoculars or a [[telescope]]. Several factors can affect what the actual limiting magnitude will be.<br />
<br />
==Theoretical Limiting Magnitude==<br />
All other factors equal, the limiting magnitude of an optical system is based solely on the aperture of the objective lens. This can be worked out with the following formula:<br />
<br />
<math>m_v\approx2.7+5\log_{10} d</math><br />
<br />
where d is the diameter of the objective lens/mirror of the optical system in mm. This formula makes the assumption that the magnification used is greater than the diameter of the objective in mm, so telescope with a 70mm objective needs an eyepiece that gives at least 70x of magnification for this formula to be accurate. It also assumes clear and dark skies <ref name="birney">Birney, D.S., Gonzales, G., Oesper, D., 2008, Observational Astronomy, 2nd ed, (Cambridge)</ref><br />
<br />
So for example, a dark adapted human eye with an aperture of about 7mm has a limiting magnitude of about 6.7 at a dark site. A 50mm set of binoculars has a limiting magnitude of 11.0 and a 127mm telescope has a limiting magnitude of about 13.0.<br />
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These magnitudes are limits for the human eye at the telescope, modern image sensors such as CCD's can push a telescope 4-6 magnitudes fainter<ref name="birney"> </ref>.<br />
<br />
==Factors Affecting Limiting Magnitude==<br />
Now the theoretical limiting magnitude calculated with the formula above is the limiting magnitude under ideal conditions. As conditions are never ideal, the value may be less than that calculated. The atmosphere above the observing site has an effect. The closer to sea level a site is, the more atmosphere one has to look through and this has a negative effect on limiting magnitude. The weather has another effect, on how transparent the air is due to water and dust in the atmosphere. Turbulence causes stars to be smeared making them seem dimmer. <br />
<br />
The telescope optics also have an effect on the limiting magnitude beyond the diameter of the objective. Poorly produced or aligned optics will spread the light of an object out and make it seem dimmer. Dirt and dust on the optics will also absorb and diffract light, again making the object seem dimmer than it really is. Higher magnification can, to a point, improve contrast by making the sky appear blacker. This works especially well on stars as their light doesn't get spread out as much under magnification as does that of extended objects.<br />
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The age and skill of the observer is also a factor. As we age, our pupils don't dilate as much as they did when we were younger, limiting how much light gets into our eye. This is less a factor with a telescope as carefully selected telescope-eyepiece combinations can compensate for this somewhat but still something to consider. Further skilled observers can generally see dimmer objects than novice observers once they learn and master techniques such as averted vision.<br />
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Finally the sky itself has a magnitude. Even at the darkest site, there is a faint glow to the sky called air glow caused by starlight being scattered by the atmosphere. Other natural phenomenon such as the Zodiacal light and aurora also cause the sky to be less dark than it could be. Beyond natural phenomenon, the light pollution from city lights causes an incredible degradation to the brightness of the night sky. Human light pollution can push limiting magnitudes to values around 4 or higher, so only the brightest stars can be seen with the unaided eye. Binoculars and telescopes also see a corresponding reduction in their limiting magnitues such that 50mm binoculars can only see around magnitude 7 or so and a 127mm telescope is limited to around 10th magnitude. <br />
<br />
==Determining Limiting Magnitude==<br />
<br />
First determine if you're using your unaided eye, binoculars or telescope. You will then need to download the appropriate map from here. If you have a postscript printer, download the .ps postscript files as they will print cleaner than the .pdf files.<br />
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Once you have your file(s), on a dark moonless night go out into your back yard with a printout of the appropriate map and locate the appropriate object – Ursa Minor (Little Dipper) for the unaided eye, the "bowl" of Ursa minor for binoculars or M67 for a telescope.<br />
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Look at the object and circle the stars you see in the sky on the map. Use a red filtered flashlight if you need it to see the map. Once you've circled the stars you can see you can go indoors and work out your limiting magnitude.<br />
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Many of the stars on the map have numbers beside them. These numbers are the magnitudes of the stars they are beside, without decimal points. The decimal points have been omitted so they don't confuse you by looking like stars. This means that a star that is magnitude 5.3 is marked as 53, 10.2 as 102 and so on. Just assume there's a decimal point before the last digit.<br />
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Find the three stars you saw with the largest numbers. These will be the dimmest ones you saw. The average of these three stars will give you a good idea what your limiting magnitude will be.<br />
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==Maps==<br />
===Limiting Magnitude Maps===<br />
The limiting magnitude maps are .pdf and .ps files. They are held in the file repository on the blog evilscientist.ca. The links below provide access to the files:<br />
<br />
{| cellspacing="0" border="1"<br />
!File<br />
!File Type<br />
!Contents<br />
|-<br />
|[http://www.evilscientist.ca/filemgmt/visit.php?lid=33 umivis.pdf]<br />
|PDF<br />
|Naked eye map in PDF format<br />
|-<br />
|[http://www.evilscientist.ca/filemgmt/visit.php?lid=32 umvis.ps]<br />
|PS<br />
|Naked eye map in postscript format<br />
|-<br />
|[http://www.evilscientist.ca/filemgmt/visit.php?lid=35 umibino.pdf]<br />
|PDF<br />
|Binocular map in PDF format<br />
|-<br />
|[http://www.evilscientist.ca/filemgmt/visit.php?lid=34 umibino.ps]<br />
|PS<br />
|Binocular map in postscript format<br />
|-<br />
|[http://www.evilscientist.ca/filemgmt/visit.php?lid=37 M67lim.pdf]<br />
|PDF<br />
|Telescope map in PDF format<br />
|-<br />
|[http://www.evilscientist.ca/filemgmt/visit.php?lid=36 M67lim.ps]<br />
|PS<br />
|Telescope map in postscript format<br />
|}<br />
<br />
=== Locator Maps ===<br />
Here are locator maps for Ursa Minor and M67<br />
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Ursa Minor<br />
[[Image:umi.png | thumb | 640px]]<br />
<br />
M67<br />
[[Image:m67_map.png | thumb | 640px]]<br />
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<br />
<References/><br />
<br />
[[Category:Observing Concepts]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2016-04-03T20:57:13Z<p>Evilscientist: </p>
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<div>Sky happenings for the month of April 2016<br />
bruary<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|New || 07 April 2016 || 11:24 <br />
|-<br />
|First Quarter || 14 April 2016 || 03:59 <br />
|-<br />
|Full || 22 April 2016 || 05:24<br />
|-<br />
|Last Quarter || 30 April 2016 || 03:29<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
<br />
April Lyrids - 22 April 2016<br />
== Other events<ref name="RASC"/> ==<br />
<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 April 2016 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
<br />
There are a multitude of deep sky objects available in the spring sky within the reach of a modest telescope even from inside a light polluted city. The globular clusters [[M3]], [[M53]] and [[M60]] are up as well as many galaxies. The galaxies [[M81]], [[M82]] are a nice pair close together in the sky. The galaxies [[M64]], [[M106]] as well as [[M51]] are high up in the sky.<br />
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If you can get out into dark skies, with a modest telescope spring is the season of galaxies, especially in the constellation [[Virgo]]. A decent star chart, modest telescope, dark skies and some patience is all you need!<br />
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[[Image:sky_apr_2016.png|15 Apr 2016 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_apr_2016.pngFile:Sky apr 2016.png2016-04-03T20:10:24Z<p>Evilscientist: Sky for Calgary on 15 April 2016 at 22:30 MDT.
{{evilcopy}}</p>
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<div>Sky for Calgary on 15 April 2016 at 22:30 MDT.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2016-03-05T01:10:01Z<p>Evilscientist: </p>
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<div>Sky happenings for the month of March 2016<br />
bruary<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
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== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 1March 2016 || 23:11<br />
|-<br />
|New || 9 March 2016 || 01:54<br />
|-<br />
|First Quarter || 15 March 2016 || 17:03<br />
|-<br />
|Full || 23 March 2016 || 12:01<br />
|-<br />
|Last Quarter ||31 March 2016 ||15:17<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Vernal Equinox 20 March 2016 at 04:30<br />
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==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 March 2016 at 22:30 MST. For this date and local time it will be similar for places in the northern hemisphere. Note that daylight savings time may be in effect for part of the monty so adjust the non-UTC times appropriately.<br><br />
<br />
The constellation of [[Leo]] is no becoming prominent to the east and is is a host of deep sky wonders. Along with [[M66]], [[M65]] and [[NGC3628]] Leo is home to a host of galaxies, most of which will require a trip outside of town to see with a modest telescope. Still overhead the magnificent open cluster [[M44]] in the constellation of [[Cancer]] as well as if you have a telescope the fainter open cluster [[M67]] is also in Cancer. [[Orion]] is now further west but it's deep sky gems are still visible. In [[Ursa Major]] a nice paring of galaxies is visible ([[M81]] and [[M82]]) which can be seen together at low power in most telescopes.<br />
<br />
A little off the beaten path are three nice [[open cluster|open clusters]] [[M36]], [[M37]], and [[M38]]. These three clusters are in the constellation of [[Auriga]] which is directly north of Orion (on top of Orion for those in the Northern Hemisphere].<br />
<br />
The planet Jupiter is now visible before midnight in the Western Sky.<br />
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[[Image:sky_mar_2016.png|15 Mar 2016 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_mar_2016.pngFile:Sky mar 2016.png2016-03-05T00:49:48Z<p>Evilscientist: Sky for 15 March 2015 at 20:30 MST for Calgary Alberta. Skill will be similar for similar latitudes.
{{evilcopy}}</p>
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<div>Sky for 15 March 2015 at 20:30 MST for Calgary Alberta. Skill will be similar for similar latitudes.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Stellar_populationsStellar populations2016-01-31T22:47:44Z<p>Evilscientist: /* Population III */ change "In theory" to "Hypothetically"</p>
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<div>Studies of the spectra of stars show that stars vary in the amount of metal<ref name="note1">Note that in astronomy, a metal is any element heavier than helium.</ref> that each contain. Stars who's spectra show prominent lines of metals are called [[#Population I|Population I]] stars. Stars who's spectra only contain weak metal lines are called [[#Population II|Population II]] stars.<br />
<br />
==Population I==<br />
Population I stars are said to be rich in metals. In this case rich is a relative term since even Population I stars have only a few percent of their mass being elements other than hydrogen and helium. As heavier elements are only formed in the interior of stars when they are undergoing nuclear fusion ([[main sequence]] stars) or during supernova explosions, Population I stars must be amongst the youngest in the galaxy, again youngest being a relative term. Population I stars tend to lie in the plane of our galaxy, primarily in the spiral arms. Our Sun is a Population I star<ref name="freedman">Freedman, Roger A and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>.<br />
<br />
==Population II==<br />
Population II stars are said to be metal poor. This suggests that that the [[nebula|nebulae]] Population II stars formed from contained little metal and hence must have been from an early time in the universe when few stars had formed. This means that the Population II stars that we see must be older than the Population I stars that we see. In order to survive this long, Population II stars that are around must be somewhat cooler and relatively small as to have survived so long. Population II stars tend to lie in the core of our galaxy as well as in the [[globular cluster|globular clusters]]<ref name="abell">Abell, George O., <u>Exploration of the Universe</u>, 4th Ed</ref>.<br />
<br />
==Population III==<br />
Hypothetically, shortly after the Big Bang, there would have been virtually no heavy elements around as stars had yet to form to create these heavy elements. This would suggest that there should have been, at one time, stars with ''no'' metal. These initial stars would have created the first heavy elements that would have then formed the Population II stars<ref name="abell">Abell, George O., <u>Exploration of the Universe</u>, 4th Ed</ref>. These stars are a theoretical construct as none have ever been observed. It may be that these initial stars were so massive that they were incredibly short lived and that they exploded as supernovae, creating the low metal nebulae that the Population II stars formed from<ref name="bromm">Bromm, V, Coppi, P, & Larson, R, ''The Formation of the First Stars'', <u>The Astrophysical Journal</u> 564:23-51, 2002</ref>.<br />
<br />
==Notes and References==<br />
<references /><br />
<br />
[[Category:Astronomical concept]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2016-01-31T22:40:07Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of February 2016<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 1 February 2016 || 03:28<br />
|-<br />
|New || 8 February 2016 || 14:39<br />
|-<br />
|First Quarter || 15 February 2016 || 07:46<br />
|-<br />
|Full || 22 February 2016 || 18:20<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
<br />
== Other events<ref name="RASC"/> ==<br />
<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 February 2016 at 22:30 MST. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The magnificent open cluster [[M44]] in the constellation of [[Cancer]] is now coming overhead and you have a telescope the fainter open cluster [[M67]] is also in Cancer. [[Orion]] is now further west but it's deep sky gems are still visible. In [[Ursa Major]] a nice paring of galaxies is visible ([[M81]] and [[M82]]) which can be seen together at low power in most telescopes.<br />
<br />
A little off the beaten path are three nice [[open cluster|open clusters]] [[M36]], [[M37]], and [[M38]]. These three clusters are in the constellation of [[Auriga]] which is directly north of Orion (on top of Orion for those in the Northern Hemisphere].<br />
<br />
The planet Jupiter is now visible before midnight in the Western Sky.<br />
<br />
[[Image:sky_feb_2016.png|15 Feb 2016 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_feb_2016.pngFile:Sky feb 2016.png2016-01-31T22:26:26Z<p>Evilscientist: </p>
<hr />
<div>Sky for Calgary (and similar latitudes) for February 2016 at 22:30 local time.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_feb_2016.pngFile:Sky feb 2016.png2016-01-31T22:25:47Z<p>Evilscientist: Sky for Calgary (and similar latitudes) for February 2016 at 22:30 local time.
{{evilscopy}}</p>
<hr />
<div>Sky for Calgary (and similar latitudes) for February 2016 at 22:30 local time.<br />
{{evilscopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2016-01-04T01:30:27Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of January 2016<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 02 January 2015 || 05:30<br />
|-<br />
|New || 10 January 2016 || 01:31<br />
|-<br />
|First Quarter || 16 January 2016 || 23:26<br />
|-<br />
|Full || 24 January 2016 || 01:46<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Quadrantids - 04 January 2016<br />
<br />
== Other events<ref name="RASC"/> ==<br />
<br />
02 January 2016 - Earth at perihelion<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 January 2016 at 22:30 MST. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
We now have the winter constellations overhead with [[Taurus]] and [[Orion]] being prominent. This brings up the unaided eye clusters of the [[Hyades]] and the [[M45|Pleiades]] over head. Both of these clusters are best either unaided eye or with binoculars. Also prominent is the [[M42|Orion Nebula]] just under the belt of Orion. All of these are worth a look. The magnificent open cluster [[M44]] in the constellation of [[Cancer]] is also coming overhead later in the evening. If you have a telescope the fainter open cluster [[M67]] is also in Cancer.<br />
<br />
A little off the beaten path are three nice [[open cluster|open clusters]] [[M36]], [[M37]], and [[M38]]. These three clusters are in the constellation of [[Auriga]] which is directly north of Orion (on top of Orion for those in the Northern Hemisphere].<br />
<br />
[[Image:sky_jan_2016.png|15 Jan 2016 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_jan_2016.pngFile:Sky jan 2016.png2016-01-04T01:20:28Z<p>Evilscientist: Sky from Calgary on 15 January 2016 at 22:30 MST.
{{evilcopy}}</p>
<hr />
<div>Sky from Calgary on 15 January 2016 at 22:30 MST.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-12-03T01:32:36Z<p>Evilscientist: December events</p>
<hr />
<div>Sky happenings for the month of December 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 03 December 2015 || 07:40<br />
|-<br />
|New || 11 December 2015 || 10:29<br />
|-<br />
|First Quarter || 18 December 2015 || 15:14<br />
|-<br />
|Full || 25 December 2015 || 11:11<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Geminids - 14 December 2015<br />
<br />
Ursids - 23 December 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 December 2015 at 22:30 MST. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
We now have the winter constellations overhead with [[Taurus]] and [[Orion]] being prominent. This brings up the unaided eye clusters of the [[Hyades]] and the [[M45|Pleiades]] over head. Both of these clusters are best either unaided eye or with binoculars. Also prominent is the [[M42|Orion Nebula]] just under the belt of Orion. All of these are worth a look.<br />
<br />
A little off the beaten path are three nice [[open cluster|open clusters]] [[M36]], [[M37]], and [[M38]]. These three clusters are in the constellation of [[Auriga]] which is directly north of Orion (on top of Orion for those in the Northern Hemisphere].<br />
<br />
[[Image:sky_dec_2015.png|15 Dec 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_dec_2015.pngFile:Sky dec 2015.png2015-12-02T15:12:34Z<p>Evilscientist: Night sky for 15 December 2015 at 22:30 MST for 51 degrees north latitude.
{{evilcopy}}</p>
<hr />
<div>Night sky for 15 December 2015 at 22:30 MST for 51 degrees north latitude.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-11-05T04:22:33Z<p>Evilscientist: /* Meteor Showers */</p>
<hr />
<div>Sky happenings for the month of November 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 02 November 2015 || 12:24<br />
|-<br />
|New || 11 November 2015 || 17:47<br />
|-<br />
|First Quarter || 19 November 2015 || 06:27<br />
|-<br />
|Full || 25 November 2015 || 22:44<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
South Taurids - 05 November 2015<br />
<br />
North Taurids - 12 November 2015<br />
<br />
Leonids - 18 November 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Moon occults Aldebaran 26 November 2015 ~10:00 - for observers in Japan, eastern Russia, northern USA, Canada, Greenland<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 November 2015 at 22:30 MST. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The autumn constellations are now well overhead and the winter ones rising. Object such as [[M31]] and clusters such as [[M34]] are now nearly overhead. Clusters [[M36]], [[M37]] and [[M35]] are now nearly overhead as well. To the eastern horizon the [[Hyades]] and [[M45]] open clusters are rising as well as the spectacular nebula [[M42]] in [[Orion]].<br />
<br />
[[Image:sky_nov_2015.png|15 Nov 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-11-05T04:22:17Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of November 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 02 November 2015 || 12:24<br />
|-<br />
|New || 11 November 2015 || 17:47<br />
|-<br />
|First Quarter || 19 November 2015 || 06:27<br />
|-<br />
|Full || 25 November 2015 || 22:44<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
South Taurids - 05 November 2015<br />
North Taurids - 12 November 2015<br />
Leonids - 18 November 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Moon occults Aldebaran 26 November 2015 ~10:00 - for observers in Japan, eastern Russia, northern USA, Canada, Greenland<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 November 2015 at 22:30 MST. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The autumn constellations are now well overhead and the winter ones rising. Object such as [[M31]] and clusters such as [[M34]] are now nearly overhead. Clusters [[M36]], [[M37]] and [[M35]] are now nearly overhead as well. To the eastern horizon the [[Hyades]] and [[M45]] open clusters are rising as well as the spectacular nebula [[M42]] in [[Orion]].<br />
<br />
[[Image:sky_nov_2015.png|15 Nov 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_nov_2015.pngFile:Sky nov 2015.png2015-11-05T04:08:47Z<p>Evilscientist: November 2015 sky for Calgary latitude at 22:30 MDT
{{evilcopy}}</p>
<hr />
<div>November 2015 sky for Calgary latitude at 22:30 MDT<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Telescope_mountTelescope mount2015-10-04T23:28:32Z<p>Evilscientist: /* Equatorial= */</p>
<hr />
<div>Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telescopes are often mounted in some fashion in order to steady the image and often to allow the object to be tracked, compensating for the Earth's rotation.<br />
<br />
==Types of Mounts==<br />
There are many different types of telescope mounts, though these types do tend to fall into a few broad categories. Fixed, transit, alt-azimuth, equatorial with some other rarer types. <br />
<br />
===Fixed===<br />
A telescope on a [[fixed mount]] is immobile and is permanently pointing in one direction (usually up at the [[zenith]]). These telescopes can be made quite large but can only observe a limited part of the sky.<br />
<br />
===Transit===<br />
A [[transit mount|transit telescope]] is fixed in [[azimuth]] but not in [[altitude]]. Usually these telescopes are set up to move along the [[meridian]] for [[astrometry|astrometric]] measurements.<br />
<br />
===Alt-azimuth===<br />
The [[alt-azimuth mount]] allows the telescope the freedom to move in two axes and thus can look at any part of the sky. With proper computer control these mounts can also track an object.<br />
<br />
===Equatorial===<br />
The [[equatorial mount]] has it's rotational axis parallel to the rotational axis of the Earth. Thus equatorial mounts can compensate for the Earth's rotation by simply rotating about this parallel (polar) axis at the rate of the Earth's rotation ([[sidereal rate]]).<br />
<br />
===Other types===<br />
Other types of telescope mount include the [[altitude-altitude mount|alt-alt mount]] where both telescope axes are a change in altitude.<br />
<br />
[[Category:Telescopes]] [[Category:Observing]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-10-01T17:00:29Z<p>Evilscientist: /* Meteor Showers */</p>
<hr />
<div>Sky happenings for the month of October 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 04 October 2015 || 21:06<br />
|-<br />
|New || 13 October 2015 || 00:06<br />
|-<br />
|First Quarter || 20 October 2015 || 20:31<br />
|-<br />
|Full || 27 October 2015 || 12:05<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Draconids - 08 October 2015<br />
<br />
Orionids - 21 October 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Uranus at opposition - 12 October 2015<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 October 2015 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The autumn constellations are now well overhead. Object such as [[M31]] and clusters such as [[M34]] are now nearly overhead. Clusters [[M36]], [[M37]] and [[M35]] are now rising on the eastern horizon.<br />
<br />
[[Image:sky_oct_2015.png|15 Oct 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-09-30T12:41:50Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of October 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 04 October 2015 || 21:06<br />
|-<br />
|New || 13 October 2015 || 00:06<br />
|-<br />
|First Quarter || 20 October 2015 || 20:31<br />
|-<br />
|Full || 27 October 2015 || 12:05<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Draconids - 08 October 2015<br />
Orionids - 21 October 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Uranus at opposition - 12 October 2015<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 October 2015 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The autumn constellations are now well overhead. Object such as [[M31]] and clusters such as [[M34]] are now nearly overhead. Clusters [[M36]], [[M37]] and [[M35]] are now rising on the eastern horizon.<br />
<br />
[[Image:sky_oct_2015.png|15 Oct 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_oct_2015.pngFile:Sky oct 2015.png2015-09-30T12:25:55Z<p>Evilscientist: October 2015 sky.
{{evilcopy}}</p>
<hr />
<div>October 2015 sky.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-09-21T22:18:53Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of September 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 05 September 2015 || 09:54<br />
|-<br />
|New || 13 September 2015 || 6:41<br />
|-<br />
|First Quarter || 21September 2015 || 8:59<br />
|-<br />
|Full || 28 September 2015 || 2:51<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Delta Sextantids - 29 September 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Partial Solar Eclipse (Antartica, Southern Africa) - 13 Sep 2015 at 6:41<br />
<br />
Autumnal Equinox - 23 September 2015 at 8:21<br />
<br />
Total Lunar Eclipse (Western Europe, West Africa, South America, Eastern North America) - 28 September 2015 at 2:51<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 September 2015 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The summer triangle is still high overhead but now past the meridian mid evening. Autumn constellations such as [[Pegasus]] are now coming into view which brings objects like the galaxy [[M31]] as well.<br />
<br />
[[Image:sky_sep_2015.png|15 Sep 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-09-02T12:27:27Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of September 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 05 September 2015 || 09:54<br />
|-<br />
|New || 13 September 2015 || 6:41<br />
|-<br />
|First Quarter || 21September 2015 || 8:59<br />
|-<br />
|Full || 28 September 2015 || 2:51<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Delta Sextantids - 29 September 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Partial Solar Eclipse (Antartica, Southern Africa) - 13 Sep 2015 at 6:41<br />
Autumnal Equinox - 23 September 2015 at 8:21<br />
Total Lunar Eclipse (Western Europe, West Africa, South America, Eastern North America) - 28 September 2015 at 2:51<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 September 2015 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
The summer triangle is still high overhead but now past the meridian mid evening. Autumn constellations such as [[Pegasus]] are now coming into view which brings objects like the galaxy [[M31]] as well.<br />
<br />
[[Image:sky_sep_2015.png|15 Sep 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Sky_sep_2015.pngFile:Sky sep 2015.png2015-09-02T12:15:01Z<p>Evilscientist: Sky for Calgary area on 15 September 2015 at about 22:30 MDT.
{{evilcopy}}</p>
<hr />
<div>Sky for Calgary area on 15 September 2015 at about 22:30 MDT.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Telescope_mountTelescope mount2015-08-30T19:44:59Z<p>Evilscientist: </p>
<hr />
<div>Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telescopes are often mounted in some fashion in order to steady the image and often to allow the object to be tracked, compensating for the Earth's rotation.<br />
<br />
==Types of Mounts==<br />
There are many different types of telescope mounts, though these types do tend to fall into a few broad categories. Fixed, transit, alt-azimuth, equatorial with some other rarer types. <br />
<br />
===Fixed===<br />
A telescope on a [[fixed mount]] is immobile and is permanently pointing in one direction (usually up at the [[zenith]]). These telescopes can be made quite large but can only observe a limited part of the sky.<br />
<br />
===Transit===<br />
A [[transit mount|transit telescope]] is fixed in [[azimuth]] but not in [[altitude]]. Usually these telescopes are set up to move along the [[meridian]] for [[astrometry|astrometric]] measurements.<br />
<br />
===Alt-azimuth===<br />
The [[alt-azimuth mount]] allows the telescope the freedom to move in two axes and thus can look at any part of the sky. With proper computer control these mounts can also track an object.<br />
<br />
===Equatorial====<br />
The [[equatorial mount]] has it's rotational axis parallel to the rotational axis of the Earth. Thus equatorial mounts can compensate for the Earth's rotation by simply rotating about this parallel (polar) axis at the rate of the Earth's rotation ([[sidereal rate]]).<br />
<br />
===Other types===<br />
Other types of telescope mount include the [[altitude-altitude mount|alt-alt mount]] where both telescope axes are a change in altitude.<br />
<br />
[[Category:Telescopes]] [[Category:Observing]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Telescope_mountTelescope mount2015-08-30T19:44:28Z<p>Evilscientist: </p>
<hr />
<div>Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telescopes are often mounted in some fashion in order to steady the image and often to allow the object to be tracked, compensating for the Earth's rotation.<br />
<br />
==Types of Mounts==<br />
There are many different types of telescope mounts, though these types do tend to fall into a few broad categories. Fixed, transit, alt-azimuth, equatorial with some other rarer types. <br />
<br />
===Fixed===<br />
A telescope on a [[fixed mount]] is immobile and is permanently pointing in one direction (usually up at the [[zenith]]). These telescopes can be made quite large but can only observe a limited part of the sky.<br />
<br />
===Transit===<br />
A [[transit mount|transit telescope]] is fixed in [[azimuth]] but not in [[altitude]]. Usually these telescopes are set up to move along the [[meridian]] for [[astrometry|astrometric]] measurements.<br />
<br />
===Alt-azimuth===<br />
The [[alt-azimuth mount]] allows the telescope the freedom to move in two axes and thus can look at any part of the sky. With proper computer control these mounts can also track an object.<br />
<br />
===Equatorial===<br />
The [[equatorial mount]] has it's rotational axis parallel to the rotational axis of the Earth. Thus equatorial mounts can compensate for the Earth's rotation by simply rotating about this parallel (polar) axis at the rate of the Earth's rotation ([[sidereal rate]]).<br />
<br />
===Other types===<br />
Other types of telescope mount include the [[altitude-altitude mount|alt-alt mount]] where both telescope axes are a change in altitude.<br />
<br />
Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telescopes are often mounted in some fashion in order to steady the image and often to allow the object to be tracked, compensating for the Earth's rotation.<br />
<br />
==Types of Mounts==<br />
There are many different types of telescope mounts, though these types do tend to fall into a few broad categories. Fixed, transit, alt-azimuth, equatorial with some other rarer types. <br />
<br />
===Fixed===<br />
A telescope on a [[fixed mount]] is immobile and is permanently pointing in one direction (usually up at the [[zenith]]). These telescopes can be made quite large but can only observe a limited part of the sky.<br />
<br />
===Transit===<br />
A [[transit mount|transit telescope]] is fixed in [[azimuth]] but not in [[altitude]]. Usually these telescopes are set up to move along the [[meridian]] for [[astrometry|astrometric]] measurements.<br />
<br />
===Alt-azimuth===<br />
The [[alt-azimuth mount]] allows the telescope the freedom to move in two axes and thus can look at any part of the sky. With proper computer control these mounts can also track an object.<br />
<br />
===Equatorial====<br />
The [[equatorial mount]] has it's rotational axis parallel to the rotational axis of the Earth. Thus equatorial mounts can compensate for the Earth's rotation by simply rotating about this parallel (polar) axis at the rate of the Earth's rotation ([[sidereal rate]]).<br />
<br />
===Other types===<br />
Other types of telescope mount include the [[altitude-altitude mount|alt-alt mount]] where both telescope axes are a change in altitude.<br />
<br />
[[Category:Telescopes]] [[Category:Observing]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Telescope_mountTelescope mount2015-08-30T19:44:16Z<p>Evilscientist: Created page with "Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telesco..."</p>
<hr />
<div>Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telescopes are often mounted in some fashion in order to steady the image and often to allow the object to be tracked, compensating for the Earth's rotation.<br />
<br />
==Types of Mounts==<br />
There are many different types of telescope mounts, though these types do tend to fall into a few broad categories. Fixed, transit, alt-azimuth, equatorial with some other rarer types. <br />
<br />
===Fixed===<br />
A telescope on a [[fixed mount]] is immobile and is permanently pointing in one direction (usually up at the [[zenith]]). These telescopes can be made quite large but can only observe a limited part of the sky.<br />
<br />
===Transit===<br />
A [[transit mount|transit telescope]] is fixed in [[azimuth]] but not in [[altitude]]. Usually these telescopes are set up to move along the [[meridian]] for [[astrometry|astrometric]] measurements.<br />
<br />
===Alt-azimuth===<br />
The [[alt-azimuth mount]] allows the telescope the freedom to move in two axes and thus can look at any part of the sky. With proper computer control these mounts can also track an object.<br />
<br />
===Equatorial====<br />
The [[equatorial mount]] has it's rotational axis parallel to the rotational axis of the Earth. Thus equatorial mounts can compensate for the Earth's rotation by simply rotating about this parallel (polar) axis at the rate of the Earth's rotation ([[sidereal rate]]).<br />
<br />
===Other types===<br />
Other types of telescope mount include the [[altitude-altitude mount|alt-alt mount]] where both telescope axes are a change in altitude.<br />
<br />
Very small telescopes, including binoculars, can be hand held. However even very small telescopes and binoculars will show a lot of shake if hand held. Because of this telescopes are often mounted in some fashion in order to steady the image and often to allow the object to be tracked, compensating for the Earth's rotation.<br />
<br />
==Types of Mounts==<br />
There are many different types of telescope mounts, though these types do tend to fall into a few broad categories. Fixed, transit, alt-azimuth, equatorial with some other rarer types. <br />
<br />
===Fixed===<br />
A telescope on a [[fixed mount]] is immobile and is permanently pointing in one direction (usually up at the [[zenith]]). These telescopes can be made quite large but can only observe a limited part of the sky.<br />
<br />
===Transit===<br />
A [[transit mount|transit telescope]] is fixed in [[azimuth]] but not in [[altitude]]. Usually these telescopes are set up to move along the [[meridian]] for [[astrometry|astrometric]] measurements.<br />
<br />
===Alt-azimuth===<br />
The [[alt-azimuth mount]] allows the telescope the freedom to move in two axes and thus can look at any part of the sky. With proper computer control these mounts can also track an object.<br />
<br />
===Equatorial====<br />
The [[equatorial mount]] has it's rotational axis parallel to the rotational axis of the Earth. Thus equatorial mounts can compensate for the Earth's rotation by simply rotating about this parallel (polar) axis at the rate of the Earth's rotation ([[sidereal rate]]).<br />
<br />
===Other types===<br />
Other types of telescope mount include the [[altitude-altitude mount|alt-alt mount]] where both telescope axes are a change in altitude.<br />
<br />
[[Category:Telescopes]] [[Category:Observing]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Category:ObservingCategory:Observing2015-08-30T19:43:52Z<p>Evilscientist: </p>
<hr />
<div>This category contains categories and articles on the topic of observing.<br />
<br />
{{Putincategory}}<br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Category:Astronomical_informationCategory:Astronomical information2015-08-30T19:43:32Z<p>Evilscientist: </p>
<hr />
<div>This [[:Category:Astronomical|astronomical]] category contains general information of an astronomical flavour that isn't directly related to observing.<br />
<br />
{{Putincategory}}<br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Flat_fieldFlat field2015-08-22T15:44:22Z<p>Evilscientist: </p>
<hr />
<div>In [[CCD]] [[astrophotography|astroimaging]] a flat field (sometimes called a flat image) is an image taken in order to compensate for variances in light sensitivity across the CCD chip. If a CCD sensor is illuminated by a perfectly flat light source, that is that every part of the CCD surface is illuminated by exactly the same amount of light, the number of photons counted by each cell in the CCD will be different. In pretty picture imaging this can cause variations in brightness across the image. In scientific imaging this can introduce significant instrumentation error<ref name="birney1">Birney, D.S., Gonzalez, G., Oesper, D., 2008, Observational Astronomy 2nd ed., Cambridge University Press, Cambridge, p173</ref><ref name="howell1">Howell, S.B., 2010, Handbook of CCD Astronomy, 2nd ed. Cambridge University Press, Cambridge, p67</ref>.<br />
[[Image:Flat_field.jpg|right|thumb|200px|A typical flat field image]]<br />
To compensate for this astronomers take a flat field image. This image is taken by pointing the optical system at a perfectly flat light source and allowing the CCD to be exposed for a period of time. This creates an image that shows not only the variance across the CCD but also any variance caused by the optical system such as dust or vignetting<ref name="birney1"/><ref name="howell1"/>. This image is then saved and used to correct any subsequent application images by dividing the application image by the flat field image<ref name="howell2">Howell, S.B., 2010, Handbook of CCD Astronomy, 2nd ed. Cambridge University Press, Cambridge, p82</ref>.<br />
==Types of Flat Field Images==<br />
There are several methods of creating a flat field image, each one has advantages and disadvantages and astronomers will often use a combination of methods in order to create a good flat field.<br />
<br />
===Dome Flats===<br />
As the name suggests, a dome flat is taken in the observatory (which is often covered with a dome). With this type of flat, a screen that is slightly larger than the aperture of the telescope is mounted somewhere in the observatory (usually on the dome) where it is evenly illuminated by artificial lights. The telescope is pointed at the screen and the flat image taken <ref name="birney1"/>.<br />
The advantage of a dome flat is that it can be taken at any time, even during the day. This means that valuable on-sky time isn't used for non-target imaging. The primary disadvantage of the dome flat is that it is often itself not flat due to variances in the lighting used and variances in the screen itself<ref name="birney1"/>. Also without special thought to the paint used on the screen, the screen may also not be truly white and thus not flat in certain filters<ref name="massey">Massey, P. and Jacoby, G.H., 1992, ASPC 23, p240</ref>.<br />
<br />
===Twilight Flats===<br />
There is a point in the sky about 20° from the zenith opposite the Sun right at sunset that is basically flat<ref name="birney1"/>. Since this point in the day is called twilight, this makes a twilight flat. The advantage to this type of flat is that it is readily available as all one has to do is wait till the appropriate time, point the telescope at the appropriate point in the sky and take the flat image. The disadvantage of this technique is that the point in time where this point in the sky is flat is limited to periods where the Sun is between 90° and 100° from the zenith<ref name="chromey">Chromey, F.R. and Hasselbacher, D.A., 1996, PASP 108, p 994</ref>. This translates into a period of time of about 40 minutes each night and it is possible to miss this window while setting up for an evening's observing run.<br />
===Sky Flats===<br />
It is also possible to use the night sky itself as a flat field. The difficulty here is that there are things visible in the night sky such as stars that get in the way of making a sky flat. The way a sky flat is made is a point in the sky with few stars is selected. The telescope is pointed at this area, the tracking turned off (so the stars drift) and the flat image exposed. This is done many times. The resulting images are combined using a mode statistic which removes the star trails<ref name="birney1"/>.<br />
The advantage of this type of flat is that the colour is always correct. The night sky is always the colour of the night sky and thus in all filters will show the correct colour. The disadvantages are that even a mode statistic may not remove all the stars, making the image non-flat and that taking a series of sky flats takes time away from on-target imaging.<br />
===References===<br />
<references/><br />
<br />
[[Category:Observing Concepts]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Flat_fieldFlat field2015-08-22T15:43:33Z<p>Evilscientist: Created page with "In CCD astroimaging a flat field (sometimes called a flat image) is an image taken in order to compensate for variances in light sensitivity across th..."</p>
<hr />
<div>In [[CCD]] [[astrophotography|astroimaging]] a flat field (sometimes called a flat image) is an image taken in order to compensate for variances in light sensitivity across the CCD chip. If a CCD sensor is illuminated by a perfectly flat light source, that is that every part of the CCD surface is illuminated by exactly the same amount of light, the number of photons counted by each cell in the CCD will be different. In pretty picture imaging this can cause variations in brightness across the image. In scientific imaging this can introduce significant instrumentation error<ref name="birney1">Birney, D.S., Gonzalez, G., Oesper, D., 2008, Observational Astronomy 2nd ed., Cambridge University Press, Cambridge, p173</ref><ref name="howell1">Howell, S.B., 2010, Handbook of CCD Astronomy, 2nd ed. Cambridge University Press, Cambridge, p67</ref>.<br />
[[Image:Flat_field.jpg|right|thumb|200px|A typical flat field image]]<br />
To compensate for this astronomers take a flat field image. This image is taken by pointing the optical system at a perfectly flat light source and allowing the CCD to be exposed for a period of time. This creates an image that shows not only the variance across the CCD but also any variance caused by the optical system such as dust or vignetting<ref name="birney1"/><ref name="howell1"/>. This image is then saved and used to correct any subsequent application images by dividing the application image by the flat field image</ref><ref name="howell2">Howell, S.B., 2010, Handbook of CCD Astronomy, 2nd ed. Cambridge University Press, Cambridge, p82</ref>.<br />
==Types of Flat Field Images==<br />
There are several methods of creating a flat field image, each one has advantages and disadvantages and astronomers will often use a combination of methods in order to create a good flat field.<br />
<br />
===Dome Flats===<br />
As the name suggests, a dome flat is taken in the observatory (which is often covered with a dome). With this type of flat, a screen that is slightly larger than the aperture of the telescope is mounted somewhere in the observatory (usually on the dome) where it is evenly illuminated by artificial lights. The telescope is pointed at the screen and the flat image taken <ref name="birney1"/>.<br />
The advantage of a dome flat is that it can be taken at any time, even during the day. This means that valuable on-sky time isn't used for non-target imaging. The primary disadvantage of the dome flat is that it is often itself not flat due to variances in the lighting used and variances in the screen itself<ref name="birney1"/>. Also without special thought to the paint used on the screen, the screen may also not be truly white and thus not flat in certain filters<ref name="massey">Massey, P. and Jacoby, G.H., 1992, ASPC 23, p240</ref>.<br />
<br />
===Twilight Flats===<br />
There is a point in the sky about 20° from the zenith opposite the Sun right at sunset that is basically flat<ref name="birney1"/>. Since this point in the day is called twilight, this makes a twilight flat. The advantage to this type of flat is that it is readily available as all one has to do is wait till the appropriate time, point the telescope at the appropriate point in the sky and take the flat image. The disadvantage of this technique is that the point in time where this point in the sky is flat is limited to periods where the Sun is between 90° and 100° from the zenith<ref name="chromey">Chromey, F.R. and Hasselbacher, D.A., 1996, PASP 108, p 994</ref>. This translates into a period of time of about 40 minutes each night and it is possible to miss this window while setting up for an evening's observing run.<br />
===Sky Flats===<br />
It is also possible to use the night sky itself as a flat field. The difficulty here is that there are things visible in the night sky such as stars that get in the way of making a sky flat. The way a sky flat is made is a point in the sky with few stars is selected. The telescope is pointed at this area, the tracking turned off (so the stars drift) and the flat image exposed. This is done many times. The resulting images are combined using a mode statistic which removes the star trails<ref name="birney1"/>.<br />
The advantage of this type of flat is that the colour is always correct. The night sky is always the colour of the night sky and thus in all filters will show the correct colour. The disadvantages are that even a mode statistic may not remove all the stars, making the image non-flat and that taking a series of sky flats takes time away from on-target imaging.<br />
===References===<br />
<references/><br />
<br />
[[Category:Observing Concepts]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Flat_field.jpgFile:Flat field.jpg2015-08-22T15:35:56Z<p>Evilscientist: A typical flat field image.
{{evilcopy}}</p>
<hr />
<div>A typical flat field image.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Celestial_sphereCelestial sphere2015-08-12T08:18:39Z<p>Evilscientist: /* Celestial Equator and Celestial Poles */</p>
<hr />
<div>[[Image:Celestial_sphere.png|right|thumb|200px|The Celestial Sphere]]<br />
The celestial sphere is an imaginary sphere around the [[Earth]] in which the objects in the sky appear fixed to. If you look at the night sky, it does look somewhat like a bowl or half sphere over the ground. This appearance gave ancient astronomers the idea that a sphere surrounded the Earth and that the [[star|stars]] were fixed to this sphere, which then rotated around the Earth. The [[Sun]], [[Moon]], and [[planet|planets]] were then thought to move against the celestial sphere around the Earth in their own orbits.<br />
<br />
Now in modern times we know that there isn't a sphere around the Earth in which the stars are fixed. The stars are all at different distances from the Earth and the ones we can see with the unaided eye are all in our Galaxy and don't rotate around the Earth, but orbit the centre of our Galaxy. That being said it is often useful to think of the sky as a sphere around the Earth for the convenience of mapping and observing.<br />
<br />
==Parts of the Celestial Sphere==<br />
<br />
There are parts of the celestial sphere that are useful to know when talking about where things are in the night sky or defining the various coordinate systems used to locate objects in the sky.<br />
<br />
=== Celestial Equator and Celestial Poles ===<br />
[[Image:Pole_equator.png|right|thumb|200px|The Celestial Equator and Poles]]<br />
If you project the Earth's equator onto the night sky you produce an imaginary line across the sky known as the celestial equator. This means that if you were standing on the Earth's equator looking due east, the celestial equator would start at the horizon, go straight up overhead and then down due west directly behind you. The height above the ground the celestial equator appears depends on how close you are (in [[latitude]]) to the Earth's equator. As with the terrestrial equator on the ground, the celestial equator divides the sky into northern and southern hemispheres.<br />
<br />
If you project the Earth's geographic/terrestrial [[Earth's poles|pole]] out onto the celestial sphere, you would then create the north and south celestial poles. Thus if you were to stand on one of the Earth's poles the and looked straight up you would be looking in the direction of one of the celestial poles (north if you were standing on the Earth's north pole, south if you were standing on the south pole). As with the celestial equator the height of the celestial pole depends on your latitude. In fact the height above the northern horizon of the north celestial pole is your latitude (change to the southern pole and horizon for south of the terrestrial equator).</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Constellation_article_styleConstellation article style2015-08-12T08:17:10Z<p>Evilscientist: add wikilink to celestial sphere</p>
<hr />
<div>==Purpose==<br />
The purpose of having a fixed style for [[constellation]] pages is to provide the end user with a consistent look. This consistent look serves to make it easy for someone to find information on the page as all constellation pages will have particular pieces of information in the same place. This makes the use of the constellation page format mandatory for all constellation pages.<br />
==Basic Format==<br />
The basic format is to have a constellation information box on the right hand side of the article. To the left of this is some basic information on the constellation such as a description of the constellation, where in the sky it is, it's history, etc. This will be followed by a section that contains a map of the constellation. Following this is a section on which [[canonical list | City Deepsky Project objects]] are located within the boundaries of the constellation.<br />
<br />
==Template==<br />
The best way to start an article about a constellation is to use the [[Template:Constellation | constellation template]]. This will allow you quickly put the information into your constellation article without having to worry about formatting. It also allows for constellation article format changing without massive re-editing of constellation articles.<br />
<br />
===Using the template===<br />
Just cut and paste the following into your article and fill in the various template parameters.<br />
<br />
<pre><br />
{{constellation<br />
|con_name=<br />
|con_ename=<br />
|con_abbr=<br />
|con_gen=<br />
|con_hemi=<br />
|con_season=<br />
|con_description=<br />
|con_map=<br />
}}<br />
</pre><br />
<br />
===Template parameter description===<br />
Here's what you put in each of the above template parameters<br />
<br />
*con_name=The IAU constellation Latin name as listed on the [[http://www.iau.org/public_press/themes/constellations/ | IAU website]].<br />
*con_ename=The IAU constellation English name as listed on the [[http://www.iau.org/public_press/themes/constellations/ | IAU website]].<br />
*con_abbr=The IAU constellation abbreviation as listed on the [[http://www.iau.org/public_press/themes/constellations/ | IAU website]].<br />
*con_gen=The IAU constellation genitive as listed on the [[http://www.iau.org/public_press/themes/constellations/ | IAU website]].<br />
*con_hemi=The hemisphere of the [[celestial sphere]] the constellation occupies, Northern or Southern. If the constellation is on the celestial equator then use Northern/Southern or Southern/Northern depending on where the majority of the constellation lies.<br />
*con_season=The season the constellation is in as viewed from the Earth's Northern Hemisphere.<br />
*con_description=A description of the constellation. Where it is, it's history, etc.<br />
*con_map=the file name of the map of the constellation. If you don't have one, leave blank.<br />
<br />
[[Category:Help]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/AntliaAntlia2015-08-12T08:15:37Z<p>Evilscientist: add wikilink to celestial sphere</p>
<hr />
<div>{{constellation<br />
|con_name=Antilia<br />
|con_ename=The Air Pump<br />
|con_abbr=Ant<br />
|con_gen=Antliae<br />
|con_hemi=Southern<br />
|con_season=spring<br />
|con_description=This constellation is in the southern half of the [[celestial sphere]]. Antlia is bordered on the north by [[Hydra]], to the east by [[Centaurus]], the south by [[Vela]] and the west by [[Pyxis]]. It is a very dim constellation, the brightest star being [[magnitude]] 4.3. Though home to a host of [[New General Catalog | NGC]] objects, the brightest is only 9th magnitude.<br />
<br />
==History==<br />
This constellation was first defined by Nicolas Louis de Lacaille in maps he created in 1756<ref name="ridpath">Ridpath, Ian, <u>Star Tales</u> Web version at [http://www.ianridpath.com/startales/contents.htm www.ianridpath.com]. Accessed 27 January 2009</ref>.<br />
<br />
<br />
==References==<br />
<references/><br />
|con_map=ant_map.png<br />
}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/AndromedaAndromeda2015-08-12T08:09:35Z<p>Evilscientist: add wikilink to celestial sphere</p>
<hr />
<div>{{constellation<br />
|con_name=Andromeda<br />
|con_ename=The Chained Maiden<br />
|con_abbr=And<br />
|con_gen=Andromedae<br />
|con_hemi=Northern<br />
|con_season=autumn<br />
|con_description=The constellation of Andromeda lies in the northern half of the [[celestial sphere]]. It is bounded to the north by [[Cassiopeia]] and part of [[Perseus]]. To the east is [[Perseus]]. South of the constellation is [[Triangulum]], [[Pisces]], and [[Pegasus]]. Andromeda's western border is with the constellation [[Lacerta]]. The primary [[asterism]] that makes up the constellation looks like a bent "V" with the brightest star in the constellation, Alpheratz, at its vertex and the arms of the V moving to the east and north. Andromeda is high in the sky in the [[autumn]].<br />
<br />
Andromeda lends Alpheratz to the asterism of the Great Square of Pegasus. The constellation is also home to the [[galaxy]] [[M31]] to which the constellation often gives it's name.<br />
<br />
==History==<br />
According to Greek mythology, Andromeda was the daughter of [[Cepheus | King Cepheus]] and [[Cassiopeia | Queen Cassiopeia]]. Queen Cassiopeia was a vain and boastful woman who claims of beauty angered the sea-nymphs. The nymphs appealed to Poseidon who promptly flooded King Cepheus' land. It was determined that only the sacrifice of Andromeda would appease Poseidon and she was chained to a rock to be devoured by a sea monster.<br />
<br />
At this point our hero [[Perseus]] wanders onto the scene. Seeing the beautiful Andromeda chained to the rock he mistakes her for a statue until he notices her hair blowing in the wind and her tears. Perseus immediately falls in love for Andromeda. This causes Perseus to make an offer to King Cepheus, in that he will save Andromeda in exchange for her hand in marriage. King Cepheus agreed and Perseus then proceeds to dispatch the sea monster when it arrives in an epic battle that, amongst other things, causes the creation of coral in the seas.<ref name="powel">Powell, Barry, <u>Classical Myth</u>, 2nd ed.</ref><br />
<br />
The goddess Athene is then said to have placed her image in the stars where she is surrounded by her mother and Perseus. She's a little farther from the sea monster [[Cetus]] as [[Pisces]] is in the way.<ref name="ridpath">Ridpath, Ian, <u>Star Tales</u> Web version at [http://www.ianridpath.com/startales/contents.htm www.ianridpath.com]. Accessed 27 January 2009</ref><br />
<br />
==Notes and References==<br />
<references/><br />
|con_map=and_map.png<br />
}}<br />
[[M31]]<br />
[[M32]]<br />
<br />
[[NGC 7662]]<br />
<br />
[[NGC 7686]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Celestial_sphereCelestial sphere2015-08-12T08:08:23Z<p>Evilscientist: Create page</p>
<hr />
<div>[[Image:Celestial_sphere.png|right|thumb|200px|The Celestial Sphere]]<br />
The celestial sphere is an imaginary sphere around the [[Earth]] in which the objects in the sky appear fixed to. If you look at the night sky, it does look somewhat like a bowl or half sphere over the ground. This appearance gave ancient astronomers the idea that a sphere surrounded the Earth and that the [[star|stars]] were fixed to this sphere, which then rotated around the Earth. The [[Sun]], [[Moon]], and [[planet|planets]] were then thought to move against the celestial sphere around the Earth in their own orbits.<br />
<br />
Now in modern times we know that there isn't a sphere around the Earth in which the stars are fixed. The stars are all at different distances from the Earth and the ones we can see with the unaided eye are all in our Galaxy and don't rotate around the Earth, but orbit the centre of our Galaxy. That being said it is often useful to think of the sky as a sphere around the Earth for the convenience of mapping and observing.<br />
<br />
==Parts of the Celestial Sphere==<br />
<br />
There are parts of the celestial sphere that are useful to know when talking about where things are in the night sky or defining the various coordinate systems used to locate objects in the sky.<br />
<br />
=== Celestial Equator and Celestial Poles ===<br />
[[Image:Pole_equator.png|right|thumb|200px|The Celestial Equator and Poles]]<br />
If you project the Earth's equator onto the night sky you produce an imaginary line across the sky known as the celestial equator. This means that if you were standing on the Earth's equator looking due east, the celestial equator would start at the horizon, go straight up overhead and then down due west directly behind you. The height above the ground the celestial equator appears depends on how close you are (in [[latitude]]) to the Earth's equator. <br />
<br />
If you project the Earth's geographic/terrestrial [[Earth's poles|pole]] out onto the celestial sphere, you would then create the north and south celestial poles. Thus if you were to stand on one of the Earth's poles the and looked straight up you would be looking in the direction of one of the celestial poles (north if you were standing on the Earth's north pole, south if you were standing on the south pole). As with the celestial equator the height of the celestial pole depends on your latitude. In fact the height above the northern horizon of the north celestial pole is your latitude (change to the southern pole and horizon for south of the terrestrial equator).</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Pole_equator.pngFile:Pole equator.png2015-08-12T08:05:39Z<p>Evilscientist: A representation of the celestial equator and the celestial poles.
{{evilcopy}}</p>
<hr />
<div>A representation of the celestial equator and the celestial poles.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/File:Celestial_sphere.pngFile:Celestial sphere.png2015-08-12T08:04:08Z<p>Evilscientist: A graphic representing the celestial sphere about the Earth.
{{evilcopy}}</p>
<hr />
<div>A graphic representing the celestial sphere about the Earth.<br />
{{evilcopy}}</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/Mass_determinationMass determination2015-08-02T14:33:32Z<p>Evilscientist: </p>
<hr />
<div>Determining the mass of an object in space is can be done one of two ways. One way if the object is being orbited by another body that is much less massive than the primary, such as a planet orbiting a star. The other way is used when two objects with relatively close masses are orbiting each other. Using these two variations on a theme, we have been able to measure the mass of our Sun, the other planets in our solar system, other stars and even whole galaxies.<br />
<br />
Both cases use a form of Kepler's third law of planetary motion, where:<br />
<br />
<math>p^{2}=a^{3}</math><br />
<br />
and p is the period of the planet in years and a is the semi-major axis of the planet in astronomical units.<br />
<br />
==Mass determination with one object much more massive than the other==<br />
<br />
If the object is orbited by a much smaller object, such as a planet about a star, moon or spacecraft about the planet then we can use Newton's form of Kepler's third law. <br />
<br />
<math>p^{2}=\frac{4\pi^{2}}{G(m_{1}+m_{2})}a^{3}</math> <br />
<br />
With <math>m_1</math> being the mass of one body and <math>m_2</math> being the mass of the other. If one body, <math>m_2</math> is much less massive than the other, it can be safely ignored, dropping it out of the equation thus:<br />
<br />
<math>p^{2}=\frac{4\pi^{2}}{Gm_{1}}a^{3}</math> <br />
<br />
At this point we can solve for <math>m_1</math> giving us:<br />
<br />
<math>m=\frac{4\pi^{2}a^{3}}{Gp^{2}}</math><br />
<br />
Since G is usually given in MKS units as <math>6.67\times10^{-11}N{m^{2}}{kg^{-2}}</math> the semi-major axis (a) and period (p) also need to be in MKS units, metres and seconds respectively.<br />
<br />
So an example: Jupiter's moon Io takes 1.769 days to make one orbit. It's semi-major axis is measured to be 421800km. From this we can work out Jupiter's mass. Converting days to seconds gives us a period of <math>1.528\times10^{5}</math>s and a semi-major axis of <math>4.218\times10^{8}</math>m. Substituting in to our equation above gives us a mass of about <math>1.9\times10^{27}</math>kg or about 318 times the mass of the Earth.<br />
<br />
==Mass determination with both objects are close in mass==<br />
<br />
For objects that are close in mass we need to do something else since the two objects will orbit about a common [[barycentre]]. As it turns out the distance from the centres of the bodies is related to the mass of the two bodies thus:<br />
<br />
[[Image:Barycentre_mass.png|barycentre]]<br />
<br />
<math>\frac{m_{1}}{m_{2}}=\frac{r_{2}}{r_{1}}</math><br />
<br />
So we can, from the ratio and Kepler's Third Law work out the mass of stars that orbit each other based on these two relations:<br />
<br />
<math>m_{1}+m_{2}=\frac{a^{3}}{p^{2}}</math><br />
<br />
<math>m_{2}=\frac{(m_{1}+m_{2})}{1+\frac{r_{2}}{r_{1}}}</math><br />
<br />
Where a is the separation distance in astronomical units and p is their orbital period in years. This yields masses in solar mass units (Sun's mass = 1).<br />
<br />
So if we observe two stars orbiting each other with a separation of 100 AU and a period of 90 years and we work out that the barycenter is 25 AU from one of the stars we can do the following:<br />
<br />
The total mass of the system from <math>m_{1}+m_{2}=\frac{a^{3}}{p^{2}}</math> is:<br />
<br />
<math>m_{1}+m_{2}=\frac{(100AU)^{3}}{(90yr)^{2}}=123</math> solar masses.<br />
<br />
Using <math>m_{2}=\frac{(m_{1}+m_{2})}{1+\frac{r_{2}}{r_{1}}}</math> nets us the mass of one of the stars:<br />
<br />
<math>m_{2}=\frac{123 solar masses}{1+\frac{(100AU-25AU)}{25AU}}=30.75</math> solar masses.<br />
<br />
Since we know the total mass of the system we can do some subtraction and find the other star's mass of 92.25 solar masses.<br />
<br />
[[Category:Astronomical concept]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/AlbedoAlbedo2015-08-02T14:32:39Z<p>Evilscientist: </p>
<hr />
<div>The albedo of an object is the amount of incident radiation that is reflected back into space by that object. It is the total amount of radiation reflected (<math>F_r</math>) into space by an object divided by the total amount of radiation that hits the object (<math>F_i</math>).<br />
<br />
<math>A=\frac{F_r}{F_i}</math><br />
<br />
The more light reflected, the higher the albedo. An object with a higher albedo will appear brighter than an object with low albedo, all other things (size, incident radiation, distance to the object) being equal. This is because the higher albedo object is reflecting more of the light back into space for us to see. A perfect white reflector would have an albedo of 1. A perfect black absorber would have an albedo of 0.<br />
<br />
==Albedo of some common objects==<br />
{| border="1"<br />
!Object!!Albedo<ref name="COSMOS_albedo"> http://astronomy.swin.edu.au/cosmos/A/Albedo retrieved on 01 Aug 2015</ref><br />
|-<br />
|Earth||0.30<br />
|-<br />
|Moon||0.12<br />
|-<br />
|Venus||0.75<br />
|-<br />
|Jupiter||0.34<br />
|}<br />
<br />
==References==<br />
<references/><br />
<br />
[[Category:Astronomical concept]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-08-02T14:32:06Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of August 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases<ref name="RASC">Information from the RASC Observer's Handbook</ref>==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 07 August 2015 || 02:03<br />
|-<br />
|New || 14 August 2015 || 14:53<br />
|-<br />
|First Quarter || 22 August 2015 || 19:31<br />
|-<br />
|Full || 29 August 2015 || 18:35<br />
|}<br />
<br />
== Meteor Showers<ref name="RASC"/>==<br />
Perseids - 13 August 2015<br />
<br />
== Other events<ref name="RASC"/> ==<br />
Venus in inferior conjunction - 15 August 2015<br />
<br />
==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 August 2015 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
Saturn is now low in the southwest and for the early evening the only planet visible. The summer triangle is now high overhead where the [[planetary nebula|planetary nebulae]] [[M27]] - the Dumbbell Nebula (in [[Vulpecula]]) and [[M57]] - the Ring Nebula (in [[Lyra]]) may be found. The [[globular cluster|globular clusters]] [[M56]] and [[M71]] are also in this region. The [[open cluster]] [[M29]] can be found in [[Cygnus]].<br />
<br />
[[Image:sky_aug_2015.png|15 Aug 2015 Sky]]<br />
<br />
==References==<br />
<references/><br />
[[Category:Astronomical]]</div>Evilscientisthttp://www.citydeepsky.com/wiki/index.php/CityDeepSky:Current_eventsCityDeepSky:Current events2015-08-02T14:21:50Z<p>Evilscientist: </p>
<hr />
<div>Sky happenings for the month of August 2015<br />
<br />
Note all [[Time and number conventions|times]] and dates in UTC unless otherwise specified.<br />
<br />
== Lunar Phases==<br />
{| border="1"<br />
!Phase!!Date (UTC)!!Time (UTC)<br />
|-<br />
|Last Quarter || 07 August 2015 || 02:03<br />
|-<br />
|New || 14 August 2015 || 14:53<br />
|-<br />
|First Quarter || 22 August 2015 || 19:31<br />
|-<br />
|Full || 29 August 2015 || 18:35<br />
|}<br />
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== Meteor Showers ==<br />
Perseids - 13 August 2015<br />
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== Other events ==<br />
Venus in inferior conjunction - 15 August 2015<br />
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==Night Sky==<br />
Note that this is for Calgary, Alberta on 15 August 2015 at 22:30 MDT. For this date and local time it will be similar for places in the northern hemisphere.<br><br />
Saturn is now low in the southwest and for the early evening the only planet visible. The summer triangle is now high overhead where the [[planetary nebula|planetary nebulae]] [[M27]] - the Dumbbell Nebula (in [[Vulpecula]]) and [[M57]] - the Ring Nebula (in [[Lyra]]) may be found. The [[globular cluster|globular clusters]] [[M56]] and [[M71]] are also in this region. The [[open cluster]] [[M29]] can be found in [[Cygnus]].<br />
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[[Image:sky_aug_2015.png|15 Aug 2015 Sky]]<br />
[[Category:Astronomical]]</div>Evilscientist