coordinates

fizzy123 · Post by **fizzy123** » Sun Mar 14, 2004 11:14 am

Hmmm..... just like to know, does any one know how get the exact right ascension and declination of a new object in the sky.

rlow · Post by **rlow** » Sun Mar 14, 2004 1:13 pm

One approximate but quick way is to mark its position on a star map, eg, Sky Atlas 2000 and read the coordinates with the coordinate-grid overlay sheet supplied. If you have digital setting circles or a goto scope/mount, you can get more precise coordinates when it is properly calibrated.

ChaosKnight · Post by **ChaosKnight** » Sun Mar 14, 2004 2:24 pm

Not sure what you are asking here.....

If you are asking how to use your setting circles to get the coordinates of a new object, you have to do a proper polar alignment. Your Dec should be set after this. Then point your telescope at an object whose coordinates you know. Then twist your RA circle until the readouts match those given in the charts. Then very quickly, point your telescope at your new object. Read off the setting circles and you have it.

Post by **Airconvent** » Sun Mar 14, 2004 11:13 pm

I think what he means is how he can identify objects in the sky by looking at it. Checking the RA and declination would be one way but you will need some background knowledge on the more common constellations.
The easier way, of course is to use a goto computer (preferabbly with GPS!).
Point your scope to it and read the info off your autostar/hand controller!

rich

fizzy123 · Post by **fizzy123** » Mon Mar 15, 2004 12:33 pm

8) ... Hmmm..... I was thinking when there is any formula to convert alt-azmiuth to right ascension and declination. etc, quote the coordinate of an object, at an instant in the sky.

Post by **weixing** » Mon Mar 15, 2004 1:18 pm

Hi,
Below is what the information that I find on the web (thinking of doing a astronomy project for pocket pc, but no time...

) and I think it should be correct, but I have no time to verified:

Hour angle
-------------
HA =LST - RA (LST->Local Sidereal Time)
If HA negative, then add 360 to bring in range 0 to 360
RA must be in degrees.

Altitude
--------
sin(ALT) = sin(DEC) * sin(LAT) + cos(DEC) * cos(LAT) * cos(HA)
ALT = asin(ALT)

Aziumuth
-----------
cos(A) = sin(DEC) - sin(ALT)*sin(LAT) / cos(ALT)*cos(LAT)
A = acos(A)
If sin(HA) is negative, then AZ = A, otherwise
AZ =360 - A

Have a nice day.