Both as a handy little tool and an exercise for my recently graduated computer programmer son, I thought it would be neat to have a little utility for converting a target's RA/Dec to Alt/Az for a given location/time.
The utility is written and is quite neat - a few fancy enhancements over what I wanted (eg. drop down editable lists of locations and targets). A bit of debugging to go, but one minor problem - it gives wrong answers, but not always?
It was based on this article:-
http://www.stargazing.net/kepler/altaz.html
My son decided not to try to program the spherical trigonometry, but rather found and inserted a routine someone else had developed and made available.
On testing against the example used in the article, the utility produces the given answer:-
"At 2310 UT on 10th August 1998, from Birmingham UK, M13 ( RA = 16 h 41.7 min, DEC = 36 d 28 min) will be found at an altitude of 49.2 degrees, and an azimuth of 269.1 degrees."
Great! So I tried it against some objects in our sky at present - the answers are obviously wrong? Finally I went back to the example of M13 observed from Birmingham in 1998 and plugged all the data into Stellarium and got the right answer (once I got the time right - Stellarium seems to want to always use local computer time, regardless of the chosen observing location - probably I haven't found how to change that as yet!)
We've tried everything we can think of, without success.
So, is there any kind C# programmer out there with a knowledge of or interest in celestial coordinates who would be willing to have a look and advise, please PM me.
As soon as we get this resolved, I'll be happy to make the program available. It's a very small windows utility. I did an earlier search and didn't find anything similar. I do know that what we are doing is embedded in most star chart programs.
Thanks, Eric
