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Hi all!

Just wanted to share an image I took yesterday. It was a nice clear sky, but at the site the light pollution is not nil, and also there was the crescent moon...

post-39678-0-29560100-1442858053_thumb.j

I am wondering, would flats help a lot eliminating these kind of gradients? I haven't had the occasion of constructing my own flatbox yet, but will some day...

Is the only real solution to this problem "wait for a real clear sky on a real dark site"?

I am only starting to feel around in the scary world of post processing... Reading a lot of very complicated procedures on different threads....

I'm pushing a person in my astroclub to prepare a course in post processing...

Problem will be that she is very well versed in PS, but I don't have that...

At the moment, almost any gradient removal I try, it eliminates also the little I captured from the nebula... :-(

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this is it, without any post elaboration, only the stack and stretch in DSS.

less gradient, but also less nebula... maybe someone really good at post could do something with it... I'll give it a go...

post-39678-0-18029100-1442864553_thumb.j

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Just stack the flats and stretch the result so you can see how even the frame is

ChrisH

ehmmm... not sure exactly what you mean... the second pic I posted is with the library flats I have (which are also from before I had the sensor cleaned... really get to make new ones...)

and DSS doesn't let me stack only flats....

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I'm no expert but I had a go. Got rid of gradient with DBE, though Gradient Xterminator for photoshop also works well. Then a couple of stretches with Curves and adjusted colour balance.

attachicon.gifpost-39678-0-29560100-1442858053a.jpg

that is absolutely amazing!!!! is that my pic??

did you do this with the original one, or the one with the flats?

it makes me hopeful, because apperently the subs I take are not all bad, but it makes me anxious to learn post production.... which seems to me a hornet's nest...

excuse the ignorance, but what is DBE?

Edited by Gerhard
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that is absolutely amazing!!!! is that my pic??

did you do this with the original one, or the one with the flats?

it makes me hopeful, because apperently the subs I take are not all bad, but it makes me anxious to learn post production.... which seems to me a hornet's nest...

excuse the ignorance, but what is DBE?

It's your data! (the second image). And its from the small file jpg so you would be able to get a better result from the larger TIFF file.

DBE is a gradient removal software feature from Pixinsight software package.

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You mention using library flats - flats should be taken at the same sessions as the images are taken to remove objects showing in the imaging train being used at the time. You can have dark libraries but not flats.

Peter

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You mention using library flats - flats should be taken at the same sessions as the images are taken to remove objects showing in the imaging train being used at the time. You can have dark libraries but not flats.

Peter

I know, but for now it's the only thing I have... I don't have a flatbox yet... I'm thinking about getting one of those LE panels for this...

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It's your data! (the second image). And its from the small file jpg so you would be able to get a better result from the larger TIFF file.

DBE is a gradient removal software feature from Pixinsight software package.

Is it difficult to remove the gradient without losing the object? That's kinda troublesome with the GIMP gradient removal technique I recently learned...

The same night as the IC5146 I took this M33, which, playing with the lighting settings springs out nicely, if it weren't for the usual gradient...

without flats:

post-39678-0-82707000-1442907636_thumb.j

with flats:

post-39678-0-99223600-1442908018_thumb.j

not wanting to ask you to do it again (and I still thank you, it was a real eye-opener! :-) ), just wondering: do you think that also with this image one would be able to lose the gradient without losing M33?

because if so, I will definitely look into buying Pixinsight and learning how to do this DBE...

because in post-production, the problem is also "what software do I use??"... there are a lot of different kinds...

Is there any particular reason you use Pixinsight?

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I've sent you a message. I would advise waiting a while before spending money on software and using the free trial periods to see what you get on with. The two main ones people seem to use is photoshop and Pixinsight. I only use a free version of pixinsight (no longer available) for the gradient removal feature. I eventually bought photoshop CC on a monthly rental basis. It doesn't have a dedicated gradient removal function but there are good filters and actions that can be added. The best is Gradient Xterminator but that is $50!

The vignetting would be much lees troublesome when you get used to taking flats that work well. I had lots of problems and tried lots of ways to take flats without too much success. Eventually I bought a light panel though if you have a laptop screen that can work.

Its a good hobby for developing problem solving skills!  and patience...

had a quick play

post-35654-0-23197000-1442912037_thumb.j

Edited by StargeezerTim
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Its a good hobby for developing problem solving skills!  and patience...

had a quick play

attachicon.gifpost-39678-0-99223600-1442908018.jpg

The vignetting would be much lees troublesome when you get used to taking flats that work well. I had lots of problems and tried lots of ways to take flats without too much success. Eventually I bought a light panel though if you have a laptop screen that can work.

fantastic result!! you used the first image, it seems?

I will definitely be making my flatbox, probably with an LE panel.

patience is a virtue I have little of, unfortunately! :-D

but "fortunately", my very limited budget keeps me in check... ;-)

just a quick question: flats should be taken in a way that the peak of the histogram is at about a third, no? I think I read that somewhere...

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just a quick question: flats should be taken in a way that the peak of the histogram is at about a third, no? I think I read that somewhere...

I think it depends. With my light panel I exposed a third along but the flats didn't work because the shutter speed was too short. So I stuck some sheets of paper on the light panel and tried different exposures. I have found that those exposed two thirds along do a better job, but that would only apply to my equipment and set up. I think you have to try different settings to see what works for you... and I have three sheets of paper attached to the panel! Lol. 

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I think it depends. With my light panel I exposed a third along but the flats didn't work because the shutter speed was too short. So I stuck some sheets of paper on the light panel and tried different exposures. I have found that those exposed two thirds along do a better job, but that would only apply to my equipment and set up. I think you have to try different settings to see what works for you... and I have three sheets of paper attached to the panel! Lol. 

ok, trusty trial & error! :-)

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Did you remember to use biases with the flats? The gradient looks very like off-centre vignetting which should be corrected by flats, but it looks very much like your library flats are not working correctly. By the way, you can take perfectly satisfactory flats using the twilight sky, you really don't need a lightbox.

NigelM

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also biases with the flats...? no... As said, I only have (for now) a library of flats I took a while ago for various ISO levels. I need to make a flatbox. Taking flats at twilight doesn't seem very practical to me, because you are very restricted time-wise... Already in this period I would have to go out observing much earlier than I do at the moment...

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I've sent you a message. I would advise waiting a while before spending money on software and using the free trial periods to see what you get on with. The two main ones people seem to use is photoshop and Pixinsight. I only use a free version of pixinsight (no longer available) for the gradient removal feature. I eventually bought photoshop CC on a monthly rental basis. It doesn't have a dedicated gradient removal function but there are good filters and actions that can be added. The best is Gradient Xterminator but that is $50!

The vignetting would be much lees troublesome when you get used to taking flats that work well. I had lots of problems and tried lots of ways to take flats without too much success. Eventually I bought a light panel though if you have a laptop screen that can work.

Its a good hobby for developing problem solving skills!  and patience...

had a quick play

attachicon.gifpost-39678-0-99223600-1442908018.jpg

Yesterday I had a go with DSE on my M33 pic. It kind of worked, but now I have a very gray background, so need to play around with the settings some more. I used the second tutorial you sent me, only the basic settings for now. Next time I have time, I'll dig somewhat deeper! :-)

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