M101, old data, new processing methods

[tomato]

Galaxy season is just around the corner and while waiting for M101 to clear a large oak tree to my North I thought I would have a go with some old data (Esprit 150/ASI 178, binned 2x2) using some of my newly discovered processing techniques, namely the EZ suite and star removal tools in PI. Still struggling with the dark halos around the bright stars.

This is around 9 hrs of L and 3.4 hrs each of RGB.

[R1k]

Stunning image. What settings (gain, offset, exposure) are you using with the 178MM?

[tomato]

Thanks for your comment. The camera settings are gain 30, offset 30, exposure 120 secs.  The cameras are uncooled versions but have been retro fitted with Peltier coolers and a temp control module so that the sensor runs at around 3 deg C.

[Rodd]

Wow.  Very nice

[GalaxyGael]

Lovely image and resolution. Regarding stars, curious to know if you have processed it without removing stars at all, especially if the black halo ringing artefacts come from processing during decon or star removal/reinsertion?

[tomato]

Thanks Colm. I used StarXTerminator to remove the stars and processed the starless image before putting them back in. I think the star removal process makes a contribution to the halos but I’ve processed other images where the end result has much less noticeable halos so my processing has a lot to do with them.

[GalaxyGael]

I find this too sometimes, to the point where I don't remove stars anymore in OSC images. Given your data set is very good quality, I'll bet processing with just light star masking might come out better and keep the stars blended in the image. when I use star removal, even when it appears to work well, it has the NB image effect (that's what i call it) where the stars always look 'added' to the image, if that makes sense. Great M101 btw, head start on galaxy season!

[tomato]

I have had a go using Starnet V2 in PI to remove the stars for processing the galaxy. I think the dark halos are less pronounced on this one? I might hold on to my £44 for the StarXterminator license for a while longer...

 

[Laurin Dave]

Nice one Steve.... I downloaded Starnet v2 yesterday and its a big improvement over an already excellent tool.

Dave

[tomato]

Yes Dave, I agree,  a definite improvement over V1. There are now two very good user friendly star removal tools available, which keep on getting better. It's a win-win for us imagers.

[gorann]

Excellent M101!

For the dark rings you often get around stars when adding them to a starless version (I use Star Xterminator), I came up with a method that I use in PS. I select all the stars (Select -> Color range, putting the selection-eyedropper in a medium bright star and put the Fuzziness slider rather high). Then I expand the selection (usually around 4-5 pixels) to cover the stars and the dark rings (see image), and feather it (1 pixel). I then use curves on the selection to just lightly make it brighter in the lower end of the histogram. That will effectively remove the dark rings (you may have to do a few attempt with different expansions).

Edited February 2, 2022 by gorann

[MKHACHFE]

First of all, stunning image. Well done mate.

Secondly, any chance of seeing your original image?

Cheers

 

 

[tomato]

Thanks for the comment. I must have about a dozen of previous attempts, the final ones were posted in this thread:
 

 

Edited February 7, 2022 by tomato
Link inserted