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1st light with WO 72 DDG - NGC6819

Deneb

By Deneb
in Imaging - Deep Sky

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Deneb

Deneb

Posted
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Hi

Took this shot of NGC6819 in cygnus last night. 50mins of each channel of RGB, taken with the 314L+, is it me or my processing ! or is That the blue channel is very strong.. as i've trying to get the bloating reduced on those stars.

(The re-process is further down)

NGC6819_314-1.jpg

Nadeem.

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shaunster

shaunster

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Hi Nadeem,

the image doesnt look right to me, it looks very unnatural did something go wrong in processing?

Also with blue stars I get this with my zenithstar 70 and they are pretty similar scopes, its just down to the cheaper optics I was told

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Deneb

Deneb

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yep your right Shuanster, it was down to reprocessing, I have been playing around with methods of processing. Here's the re-edit below:

FinalNGC6819-1.jpg

It looks better, does it not ! For alignment, stacking & correction for each channel I used CCD Stack, then converted each channel to RGB & layering them in PS.

The bloating of the blue stars - could someone point me in right direction with these please, I don't think their anything to do with UV/IR, the filters I am using are the Baader LRGB CCD Set (the expensive ones), would light pollution cause this effect with the blue channel im wandering? Any Thoughts ?

Nadeem

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philj

philj

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Hi Nadeem

The second process is more natural it looks to be a good scope.

I get a bit of blue around stars with my 102ED doublet, its a product of the coatings, not quite as colour free when imaging are they:) It gets worse with longer exposures in my experience as the fainter stars start to show it.

I use Noels actions "Remove Blue Halos Big Stars" and / or "Remove Blue Halos Smaller Stars" as required, it works really well and gives a much more natural colour.

Philj

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ollypenrice

ollypenrice

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The second one is way better. The truth is that the blue control is what you get when you pay a great deal for a refractor. It is 90 percent of the gain I found when going from Meade 127 to TEC140 or early Genesis to Tak FSQ. However, there are ways to post process the blue bloat.

-Noel's actions has a good 'reduce blue/violet haloes' routine, for one.

-Another way is to work on the affected stars just in the blue channel. Wide circular marquee, well feathered. Curves. Pin the curve at the background level then drop it steeply just above that. Further up restore it to where it was. You can write this as an action starting from a selection by Magic Wand. Thereafter one click from a keyboard shortcut sorts it. SInce there are not usually that many affected stars it is not a big deal.

Or for a really dodgy method (I would not dream of this of course!!) you can put a circular marquee over the affected star a little inside the blue halo, feather it a little, select inverse and clone stamp some background sky over the halo.

Another thought, did you refocus between colours? Also, on an imaging run, it might be worth shooting the blue at the highest elevation the object reaches during the run. Give the optics all the help they can get where they most need it.

Anyway it looks like a good little scope and a bargain.

Olly

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steppenwolf

steppenwolf

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Another way is to work on the affected stars just in the blue channel. Wide circular marquee, well feathered. Curves. Pin the curve at the background level then drop it steeply just above that. Further up restore it to where it was. You can write this as an action starting from a selection by Magic Wand. Thereafter one click from a keyboard shortcut sorts it. SInce there are not usually that many affected stars it is not a big deal.
Olly, can you show us a screen grab of the curves box based on one of Nadeem's stars in the second version, please?
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shaunster

shaunster

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Nadeem

I had a similar situation with my zenithstar, Ian King said a lot of people using the megrez 72 had a lot of success with this flattener First Light Optics - Skywatcher Field Flattener and this was the one I purchased and it works pretty well with the 383l+ but he said if you want the best then this one First Light Optics - HoTech SCA Field Flattener is better but cost 3 times more.

Blue halos is just something that comes with these scopes, nothing really gets rid of it fully but some processing does get rid of it to a large extent

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TakMan

TakMan

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That's looking better Nadeem!

Background stars are looking 'softer' with far more colour and you've suppressed those pesky blue halos a treat :)

Do you think that the focus may be a tad out - thereby not helping the situation...?

Clear skies,

Damian

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MartinB

MartinB

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Getting better with each go! Using a bahtinov mask will quickly tell you whether you have a significant difference between filters. Also a long full frame exposure will show if there are significant differences in focus across the field. Olly's point about altitude is a very important one. Blue light is scattered much more than other wavelengths at low decs so the bloat isn't always down to differences in focus

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