iraf.net

I'm just back from a Magellan run, and discovered to my chagrin that my headers all have a bogus value for the sidereal time. Everything else is fine, including the airmass, UT time, date, etc. I actually discovered this after running setjd and doslit, and somewhere along the line some IRAF task recomputed the airmasses based on my bogus sidereal times, with the result that my airmasses are now wacky as well.Given that I know the longitude, time, and data, it should be possible to put valid sidereal time values into my headers, and then run setairmass. I've gotten as far as determining that either astedit or astcalc might be able to do this, but I confess that after multiple readings of the help pages, I'm still scratching my head. Any additional guidance would be greatly appreciated.
cheers,
phil

Hi Phil,ASTHEDIT is probably the task you need, specifically the 'mst' function will help: Create a command file called 'cmd' that contains the following[code:1:1fdeb3b9ce]st = mst (@'date-obs', ut, obsdb ("lco", "longitude"))[/code:1:1fdeb3b9ce]Then running as[code:1:1fdeb3b9ce]cl> asthedit *.fits cmd[/code:1:1fdeb3b9ce]should update the 'ST' keyword (assuming the default parameters and that the obsdb value for Las Campanas is good enough for you, if not you can enter a more precise longitude). Let me know if you still have questions.Cheers and Happy New Year,
-Mike

Mike---this is great. THANK YOU!---phil

Just in case anyone encountered the same problem as I have:[code:1:3cea387b59]st = mst (@'date-obs', ut, obsdb ("lco", "longitude"))
[/code:1:3cea387b59]This above did not work for me, IRAF didn't accept the keyword, so my file now looks like this: [code:1:3cea387b59]observatory = "act"
date = imget(clget("keywpars.date_obs"))
mst = mst (date, obsdb (observatory, "longitude"))[/code:1:3cea387b59]and then it works. cheers