First effort at integration - garbage in issue?

@roblane321hotmail-com Hi Rob, the only thing I see is that the corners are darker than the center which is known as vignetting. You will need to shoot flats to compensate for that. Is there something else that catches you eye?

Wouter

@wvreeven Nope that was the observation I had  Wouter, thank you. 🙂 I suppose I have two follow up q's

1) Can I shoot the flats retrospectively?

2) is there a particular post processing step that will "restore" the darkness of the background?

@roblane321hotmail-com Rob, it is possible to shoot the flats retrospectively but keep in mind that you’ll need to put the telescope in more or less the same focus position as when taking the lights. Also dust specs my be in different positions but your image doesn’t appear to suffer from dust devils so I think you’re good.

Re q 2: you could try to create an artificial flat and divide the light by that. This, however, is not possible in APP. 

@wvreevan Ok great I'll shoot some flats and run through the flow again.

Any thoughts on why the center of the frame is so bright?

It's much less evident in the individual light frames.

@roblane321hotmail-com As a matter of fact, it looks like there is a bright ring with a darker center in the center of the picture. I suppose that your lens is a Cassegrain type? At the bottom of tab 2, make sure that "create 32 bit masters" is checked and try again. The brighter center is also part of vignetting and flats will also help solve that.

@wvreeven The lens is just a standard photography one 100-400mm G Master Super-Telephoto Zoom Lens | SEL100400GM | Sony UK 

This is the result of adding flat frames taken this morning and your recommendation re the 32 bit setting:

Seems much improved..thank you!

@roblane321hotmail-com Looks much better with at least the vignetting in the corners corrected. But I still see a ring with a dark center in the center of your image. And I see a second ring to the upper right of it.

@wvreeven I see it now you mention it - was too zoomed in on the galaxy. From your previous comment are you thinking that's an artifact of the lens / seeing conditions? 

Any specific remediation or general recommendation from here? - This is all just learning and experimentation for me! 🙂

@roblane321hotmail-com Is there more than one way in which your camera can be attached to the lens? Perhaps it was upside down when taking the flats as compared to when taking the lights?

@wvreeven nope,  just the one orientation  for connection is possible

@roblane321hotmail-com OK. When you load the master flat in APP and double click it in the files list in APP, APP will open it in the image viewer. Do you see the rings in the master flat?

@wvreeven not to my untutored eye but perhaps you do?

@roblane321hotmail-com Would you mind uploading all data to

https://upload.astropixelprocessor.com/

using upload2 for both username and password? Please create a directory called roblane321hotmail-com-vignetting and put the data in there. Then I can have a look for you.

@wvreeven Sure - you want the original raws and all the intermediate data plus final masters? Or a subset?

@roblane321hotmail-com The original raws will do. Thanks!

@wvreeven Hi Wouter - just FYI the raws got uploaded in case you want to take a peek..

Cheers

Rob

@roblane321hotmail-com Thanks, I’ll have a look tomorrow. 

@roblane321hotmail-com Hi Rob, I had a look at your data. First of all, the dark ring in the center also is visible in the lights. Here is a single sub with normalized background and saturation boosted to the max (see the control settings in the screenshot):

So it seems to be caused by the lens. Then I had a look at the master flat and a few more artifacts become visible. Here is a normalized display:

Note the spikes radiating outwards from the center. Those probably are caused by the diaphragm used. Here is the same master flat but now stretched to the max:

As you can see there is a colored ring in the center more or less corresponding to the ring in the lights. The question now is why the flats don't compensate for the ring in the lights.

I see in the EXIF data of the flats that you used an exposure time of only 0.005 seconds. Is that correct? Because that is too short for a DSLR camera. You should aim at at least 1 second. You can achieve that by covering the lens with a white t-shirt, possibly doubling layers until you get the correct illumination. What light source did you use for the flats?

@wvreeven hey Wouter - Thanks for taking the time to review and share your analysis - ok yes the flats are far too short then.

I took them just after  sunrise pointing straight up at clear blue sky with two layers of white cotton over the lens hood. The focus was set back to near as I could get what l used for the lights / darks and the ISO same (4000) F5.6   but with the camera Aperture priority mode per some suggestions I'd read  - that gave the exposure time of 1/160  - 1/250 s you saw ...I checked the histogram and thought it looked ok (not slammed to either side)  but did not check what the exposure times had been.

I'd didn't realise they need to be  as long as 1s - rookie mistake!!!  I'll shoot some more and try again.

Cheers!

Rob

@roblane321hotmail-com Hi Rob. As far as I know using very short exposure times for flats may lead to a shadow of the shutter becoming visible in the flats.