M83 Repro compensating for the UHC-S filter

[cybereye]

Hello everyone!

Armed with my DSS method of compensating for the reduction in the green channel from my UHC-S filter (debayer ratio R:G:B of 0.7:1:0.7) I went back and reprocessed some M83 data from May last year. I'd always been disappointed that I'd never been able to capture the yellow from the older stars in the central core of the galaxy. In fact most of the galaxies that I'd imaged through the UHC-S filter had looked anaemic to say the least!

So here is the reprocessed version using my new method - the data was captured using a QHY8L through an 8" newt. 33 x 5 minute subs. I think you'll agree that the colours, although more vivid, are more in keeping with what you would expect compared to my last repro of this data. Well I think so... :D

Cheers,
Mario

[LewisM]

It seems excessively purple/magenta to me, but the detail is nice.

[Poita]

That is nice data from an 8"!

[Larryp]

Lots of nice detail, Mario :thumbsup:

[jase]

Wow, what a difference Mario. The UHC-S sure cuts out the green channel as in the first image its severely clipped. At least you know its working properly given most sources of light pollution are at the 510nm (green) to 570nm (yellow) wavelengths, it sure is cutting it out. You've done a great job on the repro but I really like the details in the original image. If you stretch the green channel more to counteract the magenta cast, you'll get a balanced image. I've attached an example for reference. Unfortunately its really hard to get star colours back easily without masking, so getting those yellow stars to really shine I suspect may be an ongoing challenge with this filter. Still, its a small compromise in my opinion as you make up for it in detail. Thanks for sharing. Keep up the good work.

[RobF]

Great detail Mario. Must confess I like Jase's colour balance most though. :)

[cybereye]

Thanks everyone and thanks Jase for taking the time to play with my image. I do quite like Jase's colour balance but I also like the "vivid" colours of my latest offering - I wonder if there's a middle ground... :question:

Cheers,
Mario

[Elio]

Hi Mario, I'm Elio on astrofili.org, the italian forum you play ;)

With this kind of filter there's no way, you must take a shot in a sunny day, when the sun is high (about 12:00) to a withe sheet, with your setup, like a flat but sun illuminated...then you keep there the rgb balance...
Try to see here,
http://www.astrofototecnica.it/Tecniche/coloredslr.html

your italian is better than my poor english, sorry :shrug:

ciao :thumbsup:

P.S. you can see here the difference on my wide-image taken with an uhc filter on 50mm lens

before wb balance
http://www.astrobin.com/46945/0/

then...

http://www.astrobin.com/46945/C/

[cybereye]

Elio,

Thank you for the link - it was quite informative and I'll be out with my white sheet or card when the sun is next out here in Brisbane... it's cloudy here at the moment...again!

Ciao,
Mario