# Coordinate systems in the solar system?

I have read the wikipedia page regarding Celestial coordinate systems and searched on google, but I cannot find any coordinate systems which describe a planet's position in it's orbit. Does there exist such a system?

An example use of this system would be in locating the planets in the sky. I know that Mars is near opposition now, so I would expect that Mars' coordinates in such a system to be whatever Earth's position is +~180°.

Related Astronomy and Astrophysics News on Phys.org
russ_watters
Mentor
That's an earth centered coordinate system, not a sun centered coordinate system. And it isn't how it typically works. The normal one uses the holds the background of stars fixed. It uses right ascention and declination. http://en.wikipedia.org/wiki/Celestial_coordinate_system

What you suggest would hold the sun fixed. I guess something based on time would qualify, as the sun is due south at noon (therefore, Mars is due south at midnight right now).

I did read that wikipedia article. But where can these coordinates for celestial objects be found, then? What is Mars' value at the moment, and where could I have looked that up myself?

Thanks.

russ_watters
Mentor
Any decent planetarium program will give you the coordinates of an object. I use Starry Night.

At this moment, Mars is at:
RA: 8:39
Dec: 23 degrees 3'

D H
Staff Emeritus
I did read that wikipedia article. But where can these coordinates for celestial objects be found, then? What is Mars' value at the moment, and where could I have looked that up myself?
You might also want to read up on the International Celestial Reference Frame (ICRF, see http://rorf.usno.navy.mil/ICRF [Broken]) and Standards of Fundamental Astronomy (SOFA, see http://www.iausofa.org/index.html).

As for coordinates for various bodies, the Horizons system at JPL is a very good reference. See http://ssd.jpl.nasa.gov/?horizons.

Last edited by a moderator:
just something interesting:

http://www.atticusrarebooks.com/jferg11.jpg [Broken]

http://www.atticusrarebooks.com/jferg8.jpg [Broken]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230432371491 [Broken]

Last edited by a moderator: