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Hello,I have taken some data but the headers values have some problems.
The DATE-OBS keywords are correct (it includes the correct date and time) but the RA,DEC,EPOCH,ZD,HA,ST and airmass are wrong. I was able to use hfix to fix the EPOCH,RA and DEC but I need to fix the remaining headers. I would like to use setairmass to calculate the airmasses and replace them but it needs HA and ST and these are not correct. Is there any way to correct the airmass but by only using the information from DATE-OBS? Is there a program I can use before the setairmass that can fix the HA and ST so that the setairmass can use the corrected headers?Thank you for your time.

Assuming that by "fix the HA and ST" you mean you need to compute these values for the given DATE-OBS and observatory, then have a look at the ASTHEDIT task. You can setup an expression file using the builtin functions to compute these values as well as the airmass.

Thank you for the response.
By fixing I meant correcting and replacing and ASTHEDIT seems like it will work for me.Thank you for your time.