M20 test

[LKD]

Took advantage of as few clear nights to get 115 x 300 sec subs from my backyard in Brisbane. Would like to gather more data, seeing average HFR6.5, with transparency around 20, really need better sky conditions I think. Processing is work in progress. AG12,5 , AS6200MC. Happy to hear any suggestions on processing tips. Only the usual WBPP, plus some star reduction and unshark masking performed plus the usual curves etc in PS.

[Dave882]

Wow there’s some stunning detail and colour emerging from your data already. Probably just need a way to address the light pollution surrounding the main target. I use APP which weaves some kind of black magic to tame even some terrible gradients but I know most software has its own methods but not sure about PS unless you get the Astro-specific panel.

But man that’s gunna be a cracker when you finish!!

[willik]

Very nice trifid well done:thumbsup:

[alpal]

Hi Luke,
it's a great image as is.
with WBPP it sounds like you're in the know with the latest.

https://www.adamblockstudios.com/categories/wbpp


Any chance you could post a link to a high resolution image?


cheers
Allan

[LKD]

Any chance you could post a link to a high resolution image?


cheers
Allan[/QUOTE]

Hi Allan, thanks for the comments Hi res link https://www.astrobin.com/full/i96h88/0/

[LKD]

Here is a starless version I quite like

[alpal]

Hi Allan, thanks for the comments Hi res link https://www.astrobin.com/full/i96h88/0/[/QUOTE]




Thanks Luke,
OK - I've had a closer look at in PS.
The background seems a bit too bright.
It's coming as about 38 to 70 out of 255.
It would normally be in the range 18 to 30.

When adjusted down with curves it looks better
with more contrast but then I get a sort of dark ring around the nebula.
I don't know what is causing that -
could it be a problem with your flats
or maybe you selectively worked on the nebula with a layer mask?


cheers
Allan

[rustigsmed]

hi luke,

nice image - i also ended up with similar ring(s) with my 6200mm and found this video which may help https://www.youtube.com/watch?v=Kkg441UBNpo

Cheers

Russ

[gregbradley]

Overall it looks good but it appears your flats have not worked well.

Images taken in light pollution really need good flats as a starting point for processing.

Greg.

[alpal]

Thanks,
that led to 3 videos which I watched from Adam Block.
I have never taken dark flat frames before which solved
a similar problem to what we're seeing from Luke.
Stacking and calibration frames:

https://practicalastrophotography.com/a-brief-guide-to-calibration-frames/


Adam Block knows what he's talking about but I've never used PixInsight
before so I couldn't follow it very well.
I only ever used Deep Sky Stacker.
I found I had to muck around quite a bit with that using different
stacking parameters till I was satisfied with the final stacks.
I remember one stack came out better without any bias frames and
I never found out why.
One problem I found was that if you don't take enough dark and light
frames - cosmic ray trails or radioactive decay
can cause black lines and dots on your final stack.
Vignetting and dust doughnuts on any optical system system
means that good flat frames are vital.


A quick rough technique to fix Luke's problem is to use the magic wand in Photoshop
to select the dark ring around the nebula and make it a blurred layer mask
- then use curves to increase the lower levels -
blend it in at say 50% opacity -
however that is not for the purists.


Also - Fitswork4 - a free program -
has background flatten,
automatic flatten for nebulas
which can help.


cheers
Allan

[LKD]

Thanks for the constructive comments and advice guys.

Greg you are certainly correct, I do seem to struggle getting decent flats with the AG12.5