Starlight Xpress SXVR-H694C - Manual (Page 18)

Handbook for the SXVR-H694C Issue 1 March 2012
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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. Normal (linear) stretches can give a nice
result on many objects, but you may find that bright areas ‘burn-out’ badly with this
function. It is often much better to use a ‘Non-linear’ stretch to compress the brighter
regions, while expanding the faint data. Here is the result of a non-linear stretch on
the M42 image:
The image now looks quite impressive and I hope that you like this result from this
simple processing.
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 the noise will be
strongly increased and dark rings will appear around the stars, but a ‘Median’ filter
can remove odd speckles and a mild ‘Unsharp Mask’ (Radius 3, Power 1) will
sharpen without too much increase in noise.
Other things to try, include summing several images for a better signal to noise ratio.
Summing can be done in the ‘Merge’ menu and involves loading the first processed
image, selecting a reference point (a star) then loading the second image and finding
the same star with the mouse. Once the reference is selected, you can either add