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DS9 refuses radians as input
At the region file help page of ds9 we read that we can define position arguments in a region file by placing the numbers along with the right character, e.g. 17.845d for degrees, 16.234p for pixels.
Even though that radians are stated to be working (by placing the r character, like 12.123r), that finally DOES NOT WORK !!
I cannot understand why this happens (I even mailed them but without any answer yet!) and the only option is to convert radians to degrees before actually use them.
Sexagesimal and radian to degree conversion
A. If you want to convert sexagesimal numbers (RA=hh:mm:ss.s Dec=±dd:mm:ss) to degrees then use these relations:
RA>deg: 15 x (hh + mm/60 + ss.s/3600)
Dec>deg: ±dd ± (mm/60 + ss/3600)
These relations are pretty easy to remember since
> 1 hour the sky rotates 15 degrees (360degrees in 24 hours)
> 1 minute = 60 seconds
> 1 hour = 60 minutes = 60 seconds
> Caution with Dec: when Dec is positive you add the rest while when it is negative you subtract.
B. For radians to degrees conversion use the relation:
radians x 180o / π
