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Author Topic: Amp glow on 350D  (Read 7160 times)

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Offline ChrisLX200

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Amp glow on 350D
« on: 10:16:57, 08 August, 2006 »
Went out last night in less than ideal conditions (fat moon and misty), but I really wanted to get some more data on ngc6992. It was much cooler than the previous session ~3 weeks ago which might have helped the noise issue but I found I was getting really obtrusive 'amp glow' in the bottom-right corner of the image. My question - is it possible to selectively remove this artifact without destroying the rest of the image? I tried a few times but something always remained.
This image is a stack of 4x10min + 1x5min, dark frame substracted (not very well - it was an old dark frame as the one I took on the nght screwed up!).  Colour balanced but otherwise unprocessed.

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Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline the fordster

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Re: Amp glow on 350D
« Reply #1 on: 11:00:32, 08 August, 2006 »
Chris, the dark frame subtraction should do this automatically - The amp glow footprint (in terms of the red strip to the left as well as individual hot pixels) is always the same, so a dark frame subtraction does this well for me.

Think I read somewhere that you use imagesplus? If so, try an adaptive dark frame subtraction with a radius of 3. Another idea (all credit to Noel C for this) is to use your dark frame as a layer mask in Photoshop (apply a slight gaussian blur first) - That may give you a bit more control...

Also (as you'll know) your dark frame should match your exposure time and temperature exactly for optimum effectiveness. However, to get close, you can pop your camera in the fridge for a few mins (just to slightly lower its ambient temperature) then run off an equivalent length sub.

Hopefully one of the above may help!

Offline ChrisLX200

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Re: Amp glow on 350D
« Reply #2 on: 11:14:24, 08 August, 2006 »
Thanks Andy - yes, I should have thought of the dark frame being able to remove it (must be asleep - late night last night  :lol:)
I had a look at the dark and, although there is some brightness in that corner, it's nowhere near as bad as the final image shown here...
I'll have to take some more darks and see how they look, meanwhile I'll go have another play with the images.
Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline ChrisLX200

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Re: Amp glow on 350D
« Reply #3 on: 14:10:25, 08 August, 2006 »
Right, after a few more cups of coffee my brain began to work a little better  :D
I remembered to use PixInsight which makes it easy to remove gradients - and nasty coloured artifacts like that one. Both the extracted background and the result are shown below.

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[attachment deleted by admin]
Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline mcrossley

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Re: Amp glow on 350D
« Reply #4 on: 14:52:26, 08 August, 2006 »
Nice re-work Chris.  Now you need a flat field to rid of those dust bunnies that the background subtraction has brought out ;)
Mark
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Offline the fordster

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Re: Amp glow on 350D
« Reply #5 on: 16:12:10, 08 August, 2006 »
That's looking real nice now, Chris - Can't wait to see the final process at full size 8-)

Offline swedbird

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Re: Amp glow on 350D
« Reply #6 on: 18:30:13, 08 August, 2006 »
Woah, that´s a good subtraction. I have my own method, but this seem to be a lot better. Thanks for posting it. I´ll have a try...

It´s a very nice image also. Pinpoint stars and nice color on the nebula!

Offline ChrisLX200

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Re: Amp glow on 350D
« Reply #7 on: 19:45:07, 08 August, 2006 »
Lasse - I suppose this might be obvious but... in PixInsight, when you run the background extraction routine, don't include the nebula in the sample points - and maybe add more points where there's a well-defined artifact you want to remove. The screengrab below might help... sorry if you already knew this...!

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Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline ChrisLX200

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Re: Amp glow on 350D
« Reply #8 on: 19:59:19, 08 August, 2006 »
...the difference between excluding the nebula and not doing so is shown below (enhanced a bit for clarity...)
You lose some of the nebula otherwise.


[attachment deleted by admin]

[attachment deleted by admin]
Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline ChrisLX200

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Re: Amp glow on 350D
« Reply #9 on: 20:05:39, 08 August, 2006 »
Nice re-work Chris.  Now you need a flat field to rid of those dust bunnies that the background subtraction has brought out ;)

I'd better get the lens brush out on the chip (again...!)   Dunno where it comes from as I never leave the thing uncovered  :oops:
Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline rob uk

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Re: Amp glow on 350D
« Reply #10 on: 23:48:23, 08 August, 2006 »
nice processing tip and image chris  ;)
Quote
I'd better get the lens brush out on the chip (again...!)   Dunno where it comes from as I never leave the thing uncovered
my canon was terrible for it  :( dont some of the DSLR's now do some kind of sonic shaking to get rid of dust ..?

Offline swedbird

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Re: Amp glow on 350D
« Reply #11 on: 11:46:06, 09 August, 2006 »
Thanks Chris for the explanation! This is the far best method I´ve seen.  I do have some unwanted vinegetting from the coma corrector. The opening is only 1.3 inches and too small for a DSLR.

Update:  I just tested the DBE and it´s really magnificent!

Offline hograt

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Re: Amp glow on 350D
« Reply #12 on: 12:14:10, 12 August, 2006 »
very informative thread everyone, going to get my 350D back into action (now that M31 is rising higher)

Martin
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Offline Chris Graham

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Re: Amp glow on 350D
« Reply #13 on: 12:35:46, 18 August, 2006 »
Yeh dark frame is something i should really do as well, i always forget and need to crop the image.

Good thread btw ;)
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Offline TimH

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Re: Amp glow on 350D
« Reply #14 on: 17:49:14, 23 March, 2008 »
Just reading this thread, since I just bought a 350D. In the tools2 menu of the 350D is custom functions.
Function 2 is "long exposure noise reduction". If this is set to on, the camera will take a dark frame and do the subtraction for exposures up to 30 seconds. Ive not used it though, but Im told it does remove amp glow on each frame- Tim (fwiw) ghghghghgt
EQ6pro, Meade SN-8, OO 12" f/4, ToUcam 740,  DSIpro I

 

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