Best Way to Create Star Masks in PI

[eshy76]

Hi everyone,

I've been spending some time processing over cloudy christmas and realised the thing I find most daunting, difficult and annoying is creating star masks.  So my question is - is there a way of creating star masks (in Pixinsight preferably, but open to other ways!) which is (a) always accurate (b) relatively quick (c) repeatable?

I've worked through LVA tutorials and looked at David Ault's technique. I also have the Bracken book to go through. Main techniques seem to be:

1. Stretch extracted lightness, clip low, bring down highlights, then use Star Mask process - very inconsistent results I get with this approach
2. Similar to above, but use MMT/MLT to remove nebulosity to create support image, then use different star scale Star Masks to capture all stars and then use pixelmath to put them all onto one image - very time consuming I find, also lots of noise setting fiddling

I am very interested to see how people go about this and whether there are any neat tips and tricks to help the process! Thanks!

 

[scitmon]

I find the key to an accurate star mask is to get the shadows and midtone values right.  Aim the shadows to be a touch above your background value and midtones should be something a touch over the values of the edge for your stars.

[fwm891]

Take a look at Harry's astro shed - PI tuts star masks are covered (2 versions I think) http://www.harrysastroshed.com/pixinsight/pixinsight video html/pixinsighthomeinter.html

http://www.harrysastroshed.com/pixinsight/pixinsight video html/pixinsighthomeinter.html

[eshy76]

Thank you scitmon....I've fiddled with midtones values before, but haven't touched the shadows slider to date. Will give your tips a go!

Thanks Francis - I will take a look at those tutorials....I think I want to become a star mask ninja...or rather a general masking ninja....that seems to be key to processing and the resources you shared will no doubt help!

I generally struggle with capturing all the different sized stars...I think I might also be a bit too stringent on this - I want to mask all the stars, but perhaps the objective is protect/isolate the prominent ones?