Coordinate system

[thefallenghost]

Hi,
While I was messing around with Aladin, I discovered that decimal J2000 coordinates do not not take into account the arcseconds from their counterpart, sexagesimal J2000 (ICRS) coordinates. For example, for the coordinates 03:47:03.58 +24:09:35 Aladin shows the J2000decimal as being 56.76492 +24.15972.
However, if you were to consider the arcseconds (1/360th of a degree), you would get 56.89917 +24.24722. Is this normal? What coordinates should I prefer in Celestia?

[thefallenghost]

Could someone PLEASE answer?

[chris]

Hi,
While I was messing around with Aladin, I discovered that decimal J2000 coordinates do not not take into account the arcseconds from their counterpart, sexagesimal J2000 (ICRS) coordinates. For example, for the coordinates 03:47:03.58 +24:09:35 Aladin shows the J2000decimal as being 56.76492 +24.15972.
However, if you were to consider the arcseconds (1/360th of a degree), you would get 56.89917 +24.24722. Is this normal? What coordinates should I prefer in Celestia?

You've calculated incorrectly. An arcsecond is 1/3600th of a degree, not 1/360th. There are 60 minutes per degree and 60 seconds per minute, so 60*60=3600 seconds per degree. 24 + 9 minutes /60 + 35 seconds/3600 = 29.159722 degrees.

--Chris

[thefallenghost]

Thanks.