Expert: Philip Stahl - 12/30/2011

Question
Dear Pyhilip Stahl:

I know about the celestial coordinate system, i.e., that declination means degrees above the celestial equator and that right ascention refers the left-right postion of objects and is analogous to longitude on a map. I have a star atlas which gives coordinates of celestial objects. How do I translate the celestial coordinates on the star atlas to where I can aim an eq mounted scope to find a certain object factoring in where I live and the time of night that I want to locate the object?

Thanks

Randy

Answer
Hello,

The most straightforward way to make conversions between any two coordinate systems is to use a software program (the only other alternatives either using special clock drives that do it automatically, e.g. from celestial to horizontal coords., or using mathematical conversion formulae).

In the case of conversions such as yours, the software program I use is known as "Cybersky" which gives celestial coordinates for any date and most locations in the U.S. (or very proximate ones). Using a cursor - mouse, you can simply pinpoint any star or object on the cybersky maps you bring up (for any time), and the celestial coordinates for the object can be quickly given also in horizontal (altitude, azimuth) which fixes position in the observer's frame of reference.

You can find a free version of the software here, but after 30 days of use you can purchase it if satisfied.

http://www.cybersky.com/free_trial_version.htm

Of course, the use of this software will likely make your existing constellation-star charts redundant!