iraf.net

I'm working with the command line version of daophot (not iraf) and when I run allstar some pixels in the subtracted image are given a value of -1E19. Up to now I've been using imreplace to switch these pixels to zero so I can display the image properly.

Is there a way to get the display command to ignore the pixels with a value of -1E19? I know about using zscale- zrange- z1=?? z2=?? but that requires knowledge of what z1 and z2 *should* be. I just want display to ignore the -1E19 pixels and use zrange to do the rest.

Thanks
Vicky

What you describe can be done by setting the 'bpmask' parameter to the DISPLAY task, where the default uses the 'BPM' keyword to name the mask file, otherwise you can specify an explicit filename. To create the mask for a specific image you can use IMEXPR to create a mask of specific values, e.g.

cl\$this->_split2($m[0]) imexpr "(a display myimage.fits 1 bpmask=mymask.pl

Note the 'zmask' parameter works in reverse by specifying the pixels to be used for the zrange calculation. See the DISPLAY task help page for a description of other parameters you might use, e.g. you could turn off the 'zrange' parameter and then explicity set the min/max values to be used for the zscaling as header parameters.