PixInsight Forum (historical)

PixInsight => Tutorials and Processing Examples => Topic started by: cmassa on 2015 November 17 20:28:46

Title: Narrowband combining for SHO - linear vs nonlinear combination - advice needed
Post by: cmassa on 2015 November 17 20:28:46

I've recently started narrowband imaging with my Atik 383L+. I'm trying to process a set in the SHO palette. Where is the better point to do the channel combination - while still linear (but after gradient removal, linear fit), or later after further processing (stretching, noise reduction, etc...) in the nonlinear stages? I've been trying ratios but have read 6:1:3 is the usual mix for SHO. I'm having trouble with the entire image turning out magenta unless I unlink colors in STF. I'll keep playing with it.

Thanks for any advice,
Chris

Title: Re: Narrowband combining for SHO - linear vs nonlinear combination - advice needed
Post by: pfile on 2015 November 17 21:49:08

i do the channel combo when linear. check this thread for a very nice/easy SHO narrowband flow by RickS:

http://pixinsight.com/forum/index.php?topic=7751.0

rob

Title: Re: Narrowband combining for SHO - linear vs nonlinear combination - advice needed
Post by: jkmorse on 2015 November 18 09:08:37

Chris,

Rob's suggestion is a great way forward.  Another option which is my standard, is to wait until the non-linear phase and use the SHO-AIP script.  As to settings, I usually go 80/20 SII/Ha for Red, 80/20 OIII/Ha for Green and 100 OIII for Blue.  Juan Conejero calls this a more ‘natural’ representation and I find it works well, though I usually tweak the results using the hue button in CurvesTransformation and, if the green is still too strong, applying a dose of SCNR.

Best,

Jim