I would like some expert opinions, or suggestions on my images that I have taken over the last few months.
I am posting this image for your viewing, the problem has been (exaggerated) so that it shows the problem that occurs.
After processing correctly in Image Plus, with ICNR and Flats, etc I end up with a combined image, this seems all OK.
However when I start to use Digital Development, and say, use the auto button, or any of the other sliders, I end up with an Image that is always much brighter in the central region of the image.
All my images are taken through the Takahashi FSQ-106 with the Canon 5D, and also I have a Hutech LPR Filter behind the rear lens of the Tak.
I always have to darken the final image to get rid of this central issue, which gets rid of heaps of detail.
Would any of you good folk have an answer, and/or a suggestion, am I doing something wrong here, in my processing or the actual capture.
Could it be a light pollution issue, could it be the filter, I'm really stumped on this one.
The Image below is a aligned/stacked image of 16 exposures at 6 minutes each,at 400 ISO.
Thank You, any suggestions would be greatly appreciated.
Man, way cool. I want what he is smokin.
Seriously though Leon, I agree with Mike, that is until you tell me you take flats and they are subtracted correctly. Do they look OK before you hit the DDP?
Gary
1. Do you adjust your focus, camera position or anything between taking your lights and taking your flats?
2. What is the spread of the histogram of your flats? ie all down the left hand end, in about the middle spread narrowly but evenly, all up the right hand end.
3. Have you tried not doing the DD and taking the image into PS and doing an AV (anti-vingetting) mask?
( I just re-read what I wrote. I mean anti-vignetting, not anti-annabelling )
Hi Guys I appears that you all think that it maybe the Flats, and/or the way they are taken, so we will go there first.
I take Flats, usually on each evening of imaging, fresh ones so to speak.
I wait till after sunset, about 15 minutes, take 16 images at the same ISO as my lights will be, using the AV setting on the 5D, with the scope pointed straight up into the dull blue heavens.
Once captured I Medium Combine then in Image Plus, when the process is finished, I end up with a master flat, use Luminance and Gamma setting to grey scale, and there you have it.
This Master Flat is then mixed in the auto imaging process in Image Plus, with the lights, and so the process continues.
A combined image is created, as you all are aware.
Paul, to your 1st question, the answer is no, nothing changes in the imaging train.
On the image I can see a dust bunny which should not be there if the flats were taken and applied correctly. I can also see the dust bunny in the flat you supplied.
A dumb question but the flats should be taken at the same focus and camera orientation as the lights. You do do this?
Thats not a flat, its ummm, too flat. With a large sensor and 80mm scope, id expect a large bright circle in the middle (its not like that, which is why you have a bright circle in your image), and some donuts. Im not sure where to start, is the image brightness a 3rd way up the histogram?.
Paul yes mate the orienation of the camera is the same as when taking the lights, however looking at all your responses it appears that I should change the way the I actually capture the flats in the first place, I will work on that.
Mike I will do that later, run out of time now, but the answer is yes it appears the same with or with out Flats, but i will run the experiment later and chech that for sure and post.
I always have to darken the final image to get rid of this central issue, which gets rid of heaps of detail.
hmmm I've noticed your images are usually darkend Leon and assumed your monitor calibration was the prob, but now I understand the issue.
I'm not sure why it's happening, it looks like the flats aren't being applied at all since the dust spots are still present.
Quote:
Originally Posted by Bassnut
Ahh, no, dont take flats with AV, they are over exposed. Take them manually with the exposure set to a 3rd of the AV exposure.
Quote:
Originally Posted by Bassnut
Paul
Flat exposure should be a 3rd up the histogram, 15-20,000 ADU
I agree with Bassnut and here's how I take flats.
Put the DSLR in P (Program Mode).
Set ISO to 100
Point it to a neutral part of the evening/morning sky
Take an exposure and check the histogram is 1/3 rd of the way up.
Usually I take between 11 and 15 (odd number) of flats - median combined.
Another thing you might like to try is Deep Sky Stacker with your set of data.
See what the result is, this will confirm whether your method in IP is applying flats correctly.
I strongly suspect though that somewhere along the line your flats are not being applied at all, check your procedure against the tutorials in IP and make sure all the steps correlate.
If it's not flats related, which it may not be going from your uncalibrated image (which looks the same), it must be something on the surface of your lens (smudge) or on the filters?
If it's not flats related, which it may not be going from your uncalibrated image (which looks the same), it must be something on the surface of your lens (smudge) or on the filters?
It's very nasty.
But Mike the flats should be picking up any blemishes the lens/filter may have.
The flats themselves are the 1st problem, its almost smooth dead flat, its not compensating anything, its totally neutral and will have no effect. Ive never seen a flat like this. Even if you are applying it correctly, it will have no effect. Take them again in manual as described above and see if that makes a difference. You should get a bright circle exactly like in your images (thats its point, to have the same circle to cancel the one in your image out).
Thank you all, I will do the whole procedure again as suggested.
as You have all mentioned the flats don't seem to be applying at all, so I will also check the program, and just see if I am actually doing this correctly.
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I just re-read what I wrote. 
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