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I thought I would try the new ArcsinhStretch process in PixInsight on some recent data of M33 taken with an ED80DS+Atik414ex osc. Prior to applying the process I used DynamicCrop, DBE, BackgroundNeutralization, ColourCalibration, and TGVDenoise (the latter I am very much a novice). One application of ArcsinhStretch produced this result:


I also took Luminace and Ha in the same imaging session but the above is just from the osc.

I have tried to emulate the result in Photoshop using the procedure in a recent post by @sharkmelley but so far I've failed to get any where near this so I must be doing something wrong. I've added my tif file of the pre-stretched image in case anyone wants to have a go.

This is an image of the PI workspace showing the settings I used.


As ever any help, suggestions, comments would be much appreciated.

Thank you for looking.




Edited by Adreneline
Typo corrected.
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Thanks for the TIF file - that was very useful. Galaxies often benefit from an iterative application of PixInsight ArcsinhStretch.  For instance, if you perform two successive stretches of 7 giving a total stretch of 7x7=49 the galaxy will actually appear brighter than if you do a single stretch of 49.  Or even do 3 successive stretches that multiply up to 49.

This image seems to be a tough one to do using my colour preserving stretch in Photoshop.  I'll play around with it a bit further.


Edited by sharkmelley
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I played around with it a bit further using the colour preserving stretch in Photoshop - the problem was the background still being too bright.  It actually works very well but only after you have first subtracted a bit more background using "Levels".    A setting of 4 for the black seemed to work well.


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5 minutes ago, sharkmelley said:

For instance, if you perform two successive stretches of 7 giving a total stretch of 7x7=49 the galaxy will actually appear brighter than if you do a single stretch of 49.  Or even do 3 successive stretches that multiply up to 49.

Thank you for the advice Mark; I'll give it at a go with repeated applications and see how it compares.

I will be interested to see what you make of my tif file in PS. It's not the best of data (23 x 300s) but seeing in the East Midlands is rarely favourable.

Thank you.


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