Screen Ruler

FITS Keyword

Usage:

CROTA1

CROTA2

When FITS files are dragged and dropped onto the FITS files area of the Control window, the first FITS file that contains either the CROTA2 or CROTA1 FITS keyword is used to extract the image rotation value from that keyword. The Image Rotation° value on the Control window is loaded with the negative of the keyword value. CROTA2 is used in preference to CROTA1 if both are present. They should both contain the same value. If neither are available the Image Rotation can be manually entered from the Control window.

DATE-OBS

TIME-OBS

Used to extract the exposure date and time from FITS files in the FITS files area of the Control window.

If DATE-OBS is present and in ISO 8601 long format ('CCYY-MM-DDThh:mm:ss[.sss...]') the date and time are used as the exposure time.

If DATE-OBS is present and in ISO 8601 short format ('CCYY-MM-DD') or old 6 character FITS format ('DD-MM-YY') then the TIME-OBS value is combined with the DATE-OBS value and used as the exposure time. 

The exposure time and the exposure duration are combined using the FITSDateType setting to calculate exposure start and end times.

EXPOSURE

EXPTIME

Used to extract the exposure duration (in seconds) from FITS files in the FITS files area of the Control window.

EXPOSURE is used in preference to EXPTIME for the exposure duration. If neither are present then a value of 0 is used.

The exposure time and the exposure duration are combined using the FITSDateType setting to calculate exposure start and end times.