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is the st in setairmass of astutil local st or greenwich st?

Poon Helen wrote on Feb 28, 2009

is the st in setairmass of astutil local st or greenwich st?

I actually don't have st in the image header, I need to convert JD to st. If there is anyone who know the formular please tell me. I tried to search for the answer on the net but couldn't find a suitable answer.

Mike Fitzpatrick wrote on Feb 28, 2009

The ST is local to the observatory location that you specify.

As for converting JD: If you have a date/time of observation in your header (e.g. a DATE-OBS keyword), then see the ASTHEDIT task in ASTUTIL as a way to use these to compute the ST.

-Mike

Last post on Feb 28, 2009