Starlight Xpress SXV-M7C - Manual (Page 17)

Handbook for SXV-M7C Issue 1 June 2004
17
pollution is orange or green in colour (sodium and mercury light) and may be
removed by reducing the red and green offsets in the colour balance menu. It is best to
look at the blue histogram and note the approximate offset of the main peak above
zero. Now slide the ‘Offset’ of the Red histogram until the pointer is about the same
distance below the main peak as is the blue peak above zero. Do the same for the
Green histogram offset and then click on ‘Apply’.
4) The bright background should now look reasonably neutral in colour, although
‘colour noise’ makes it look mottled. If necessary, slightly trim the balance again until
you think the colour is as near grey as possible. It is now time to process the
‘luminance’ (brightness and contrast) of the image to get the best visual appearance.
First, use the ‘Normal’ contrast stretch to darken the background by setting the
‘Black’ slider just below the main peak of the histogram. Alternatively, you can use
the ‘Remove Background’ option to let the software decide on the best setting. This
will greatly reduce the background brightness and the image will begin to look rather
more attractive. You can now try brightening the highlights with another ‘Normal’
stretch, in which you bring down the ‘White’ slider to just above the main image
peak. The best setting for this is rather more difficult to guess and you may need
several attempts before the result is ideal. Just use the ‘Undo last filter’ function, if
necessary, to correct a mistake.
5) The image will now look quite impressive and I hope that you are pleased with
your first efforts! Further small refinements are usually possible and you will become
expert at judging the best way to achieve these as your experience increases. As a
rough guide, the ‘Filters’ menu can be used to sharpen, soften or noise reduce the
image. Strong ‘High Pass’ filters are usually not a good idea with deep sky images, as