Formula wanted...

I want to be able to plug in these values into a formula:
Latitude
Longitude
Time
Day
Month

I want to output the RA and Dec of a point at due south on the horizon.

Anyone know how this could be done??

Regards & Thanks,

Not too sure what your trying to do, maybe have a look at the following:

home.att.net/~srschmitt/planetorbits.html

Here's another link to useful astronomical formulae, but I don't think what your looking for is here either:
home1.stofanet.dk/astro/Astronomy.pdf

Michael,

I am a huge fan of Chris Marriott's SkyMap Pro. I have the demo version (V8) and which will do what you ask very easily. Although he is now up to V11, I know for certain there is still a free demo available and which will allow what you seek very easily.

Thanks Anthony.
I've downloaded the demo of V11.
Where in the program do I get that function I'm looking for?

Hi Michael,

Set up your latitude and longitude by pressing on the globe icon on the far left (vertical) side bar. If you wish a time different than that of your computer's clock, use the TIME drop-down menu to forward/advance time by year/month/day/hour/minute/second ... there is a little counter on the left to the TIME drop down menu where you can change the increment from a default of 1 to whatever you like (ex. "10" so that you can advance, for example, the minutes in tens of minutes).

Then click on the "S" icon so that you will be viewing the southern sky ... and move your mouse to any portion of the "sky" and watch the RA/Dec change on the fly on the status bar at the bottom of the screen.

Oh yeah, go into the Preferences and activate RA and Dec to be displayed in the status bar which runs horizontally across the bottom of the screen.

I hope I did not confuse you ... it really is very trivial and precisely what you are looking for since you can advance date/time forward or backward at will (when you load the software, the system clock determines the initial date and time) and the mouse becomes "live" with a constant refresh of the RA/Dec as you move the mouse.

Thanks Anthony. That's works nicely.
Actually, the more I think about it, the DEC at a point on the horizon at due south will always be (my Latitude minus 90) degrees.
So really, it's only the RA that varies during the course of the day, correct?