Quote:
Originally Posted by lockyerlad
I am a vey keen newby at astrology, with a 10" dob. reflector. Have downloaded lists of items of interest to examine with the RA and Dec details and have looked at numerous articles on the subject, but have a problem with understanding RA, Dec is OK.
I understand the comparison with longitude and RA, but how do I find a listed object e.g. NGC104 47 Tucanae at RA 00 24.1 and Dec -72.05.
The 0 point is where the vernal equinox occures and you move east by hourly intervals, 1 x hour = 15o but unless you know the exact vernal equinox point how do you know where to look, especially when it all changes by the hour.
Is this navigation system only for equatorial mounted scopes.
|
Brian, with your dob it is easier to work in altitude and azimuth. You are right that to work out where a given RA is you need to make allowance for the time, but then the alt/az changes with latitude, and through the night and day by day too.
Free programs like Stellarium, Cartes du Ceil, C2A and Halo Northern Sky will convert RA/Dec to Alt/Az for you. For instance, now and here, for NGC104 CdC gives:
Visibility for your observatory:
Castle Hill 2012-10-29 22h01m56s ( AEDT )
Universal Time: 2012-10-29T11:01:56 JD=2456229.95968
Local sidereal time:23h38m38s
Hour angle: 23h13m 55s
Azimuth:+174?20' 47"
Altitude:+51?15'07"
Circumpolar
Culmination: 22h54m +51?44'