Applying vignetting correction

Vignetting correction can be done to mcats as well as to the images. These programs can also be run using the menu providing program "mahacode". To run the programs you need to have ~aam/dposs_bin/ in the path.

Correcting mcats

To apply vignetting correction to a matched catalogue, generate the mcat for the required plate using Steve's SCO_CODE and then follow it up with mahacode:

mcat_vig_corrector.pl oldmcatdir newmcatdir

The following uncalibrated magnitudes are updated: Mag, MTot, MCore, MAper, MIso, CX. Of these, all but CX are 1000 times their actual values. The quanta of change made is noted in a separate column. Thus three new columns (61-63 for a standard mcat) are used to put the changes. The columns are called VigJ, VigF and VigN. Once the newmcat is made the old one is removed (if you own it).

Correcting blocks

To correct image blocks from the hpss and make a big image, run:

vig_correct_blocks.pl dirpath/xYYY

where x is either j or f or n and YYY is a valid plate number. It is assumed that the t????.fits file are in the directory dirpath/xYYY. The resulting file will be dirpath/xYYY-full.fits. The files dirpath/t????.fits are removed once the corrected plate is ready.

Correcting preassembled plate

To correct a preassembled plate, run:

vig_correct_plate.pl dirpath1/assembled.fits dirpath2/corrected.fits x

where x is either j or f or n. You should have write permission for directory dirpath2. The uncorrected file, dirpath1/assembled.fits is not automatically removed.

Details on how the correction images were made

Last Outdated: 11 Nov 2000