Subchapters:

Images in 3 colors

Once you have 3 images of the same object in various filter (or emission lines), you can generate BMP images in false colors:

   IDL> restore,'images_3colors.xdr'
   IDL> size_im = (size(im_hbeta)[1]
   IDL> imt = bytarr(3,size_im,size_im)
   IDL> imt[0,*,*] = bytscl(im_hbeta) ; Hbeta Blue
   IDL> imt[1,*,*] = bytscl(im_o2) ; [OII] Green
   IDL> imt[2,*,*] = bytscl(im_o3) ; [OIII] Red
   IDL> write_bmp,'im.bmp',imt
   IDL> write_bmp,'im2.bmp',rebin(imt,3,size_im*2,size_im*2)