A second tutorial on v2 of the Generalised Hyperbolic Stretch (GHS) script by Mike Cranfield for Pixinsight users. In this tutorial, an emission nebula image that fills the frame and spans a large degree of dynamic range is stretched. Starting with the initial stretch of a linear image and continuing with intermediate stretches, I show how to zero in on the parameters needed for the transform equations can be determined. Along the way, the importance of contrast placement is emphasized and how to display dim nebulosity while protecting stars is illustrated. Finally, the ability of the script to stretch saturation to restore or enhance a colour image is shown.
Mike has created a fantastic environment in which to apply the hyperbolic stretch transforms, with many features that are described in these follow-up videos, as well as other videos hosted on the https://ghsastro.co.uk/ website. You can obtain the script from this website, and can easily install it into Pixinsight. Mike and I think this is an excellent addition to your image processing tool kit - and it's free.
