Saturday, January 30, 2010

2010 Mars Oppostion

Last night Mars was at oppostion.  When a planet is at oppostion, it means that the Sun is opposite the planet in our sky.  In other words, if one looked down at the solar system from above, one would see the Sun, Earth, and Mars in a straight line (with Earth in the middle).  Interestingly, Mars comes to oppostion slightly after the time of Mars closest approach to Earth.  Closest approach of Mars and Earth happened on January 27th when the planets were separated by .664 Astronomical Units, or 99.33 million km.  This is due to the planets orbital geometry (specifically, the eccentric elliptical orbits and orbital inclination). Another less well known factor is the influence of the Moon which makes Earth move around a common center of mass.  If this technical information is interesting to you and you would like to know more, I suggest you check out the Students for the Exploration and Development of Space (SEDS) website on Mars Oppositions.

I was able to observe Mars last night, through a solid layer of high thin clouds.  The cloud cover was fairly thick with Mars, Sirius, and only about 6-8 other stars visible.  The full moon was about 6.5 degrees from Mars, and there was a beautiful halo surrounding the full moon, with Mars inside this Halo.  While the clouds and moonlight essentially compromised the transparency, the atmosphere was quite stable.  To the right is a simulated image of Mars from the freeware program Winjupos representing the time of my sketch.  I brightened the image to simulate the effect of the cloud cover and resulting scattered light.  Below is my sketch:

Instrument: TEC 140mm APO
Time of sketch 0320 UT, Jan. 30, 2010

Central Meridian: 87.5
RA: 8h 53m 39s  Dec:  22 deg 11' 4"
Illumination: 100%       Magnitude: -1.3
Distance: .665 AU (5.5 light mins)    Size: 14.1 arcseconds

Another nice online source of Mars information is William Sheehan's The Planet Mars: A History of Observation and Discovery.  The University of Arizona Press has made this book available free online!

Finally, Ralph Aeschliman Planetary Cartography and Graphics provides excellent maps of Mars that are available for download.

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