fishonkevin
member
Reged: 04/29/07
Posts: 99
Loc: Michigan
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I spent the last 10 days at my cottage in N. Michigan and was able to collect some very good data. The nights were clear and cold. I was able to collect 10 minute subs no problem on M33. But after processing I found that my darkframes could not eliminate tha ampglow in the bottm right and left corners of the picture. Here are the particulars of the photo and a link to the photo:
16 x 10mins, @ISO 1600
20 Darks, Dark Flats, Flats, Bias( Median Combined )
Stacked in DSS, Final Adjustments in PS2
Canon 350XT modified, w/ Astronomik CLS Filter
W.O. Zenithstar 105mm, @ f/7
Guided Using PHDguide/ Orion SS Autoguider / Orion ST 80mmm / Losmandy GM-8 Mount
http://farm3.static.flickr.com/2545/4117437499_8bd7d8d1d3_b.jpg
I' looking forward to your help/ideas.
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Kevin
W.O. ZS 105
Meade AR-5
GM-8
LXD-55
Rebel XT Modified
Quantaray 300mm Mirror Lens, Ziess 135mm, Sigma 24-60mm APO
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Stardaug
professor emeritus
Reged: 08/03/08
Posts: 549
Loc: Ontario, Canada
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I've had the same issue with amp glow and darks in DSS. It does not subtract the amp glow. I never found a solution to it other than using Maxim DL which does subtract the amp glow from my subs using the dark frames when calibrating.
It would be nice to understand why DSS does not process the darks properly, for some people anyhow.
Cheers.
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"Keep looking up!"
Shawn / Ontario, Canada
Celestron CPC800 SCT w/XLT & GPS // Skywatcher Equinox 80ED F6.25 500mm APO // Canon Rebel 350XT unmodded // Milburn EQ Wedge (a Meade model modified to fit my CPC)
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1343
Loc: Boston 42° 16' N 71° 08' W
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Given that amp glow is generally much brighter than that when not calibrated, it's clear that substantial subtraction is taking place. My guess would be that your darks don't quite match your lights, i.e. that the sensor was colder during the darks, or that they weren't as long.
As for correcting it, the Dynamic Background Extraction tool in PixInsight LE is generally fairly effective on this kind of thing. There are a few tutorials out there on how to use it.
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
Orion Starshoot Autoguider
QHY8
Philips SPC900NC
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Clay Kessler
sage
Reged: 04/16/07
Posts: 215
Loc: Manchester MI
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Kevin,
Gradient Extractor will help this issue. I get some amp glow on my shots from time to time and GX works very well.
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Best Regards
Clay Kessler
www.ssoastro.org
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s58y
Postmaster
Reged: 12/12/04
Posts: 5634
Loc: Eastern NY
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Images Plus seems to work pretty well to subtract amp glow for my 10 minutes subs (ISO 800) with a Canon 30D. My darks and lights are matched to within a few degrees, so not a lot of scaling is required.
I suppose the ideal solution is to get one of the newer DSLRs, that doesn't have much amp glow. 
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
http://www.flickr.com/photos/s58y/
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Pierre Stromberg
sage
Reged: 02/07/08
Posts: 213
Loc: Woodinville, WA
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I have a Nikon D50 and I have the same problem. I never got DSS to work effectively so I've tried my patience and turned on noise reduction during my long exposures. It's effective but it does halve the time I take for exposures.
Pierre
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1978 orange tube Celestron C8
1990's Celestron C90
Astro-Tech AT66
Atlas EQG with EQMOD
Nikon D50
DMK31AU03.AS
Homepage: Explore the outer limits of human belief
http://www.paranormalamerika.blogspot.com
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fishonkevin
member
Reged: 04/29/07
Posts: 99
Loc: Michigan
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Hi Folks,
Thanks for all the info. Lights and darks were acquired over 2 nights. I was shooting other objects, so I had to space my capture time accordingly. But the ambient temps reached lows of 25*F on both nights. But since M33 was the first target both nights I assume the temp. was warmer than when I shot the darks.
Clay, is that SVG "Gradient Extractor"?
I have ImagesPlus 2.10, I don't use it much anymore since it won't open .cr2 files. I am going to convert the raws to tif and see what I can get with that. I'll let you know the results.
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Kevin
W.O. ZS 105
Meade AR-5
GM-8
LXD-55
Rebel XT Modified
Quantaray 300mm Mirror Lens, Ziess 135mm, Sigma 24-60mm APO
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Alnitak2009
member
Reged: 04/10/09
Posts: 39
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Hi Kevin, I too had a problem with amp glow especially after each consecutive shot. If you turn your camera off after each image for the same duration and let it cool and then turn it on and continue to take another image, then perhaps the amp glow and even hot pixels would greatly diminish. I for one do not have a remote timer for my camera, just the standard remote, so I have to count the minutes. Each exposure is of a slghtly different duration so for me to do dark frames may not work with the amp glow very effectively. So I turned on my noise reduction on the camera and it ensures the dark frame is exactly the same duration. I don't have to worry about taking dark frames later especially when I don't have much time to image.
I no longer have the annoying amp glow as when the noise reduction is off.
Don
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zAmbonii
Pooh-Bah
Reged: 01/19/08
Posts: 1029
Loc: Ypsilanti, MI
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Quote:
Hi Folks,
I have ImagesPlus 2.10, I don't use it much anymore since it won't open .cr2 files. I am going to convert the raws to tif and see what I can get with that. I'll let you know the results.
I dont think that converting to tif will work since to *properly* calibrate images using darks/flats/offsets you need the RAW files.
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Check out my Astrophotos on Flickr
C6-N 150mm f/5 Newtonian
CG-5 ASGT mount
Canon 300D self modded + IDAS LPS-P2 FF
Meade 70AZ + Meade DSI for autoguiding
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Spoonsize
Vendor/Clothing
Reged: 08/27/04
Posts: 3334
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I've experienced the same thing. I found that I have to use the same program for both capture and preprocessing. ie: If I use Nebulosity or Envisage to capture I cannot use Images Plus to stack and vice versa. So I do all with one and then post process with photoshop.
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Clay Kessler
sage
Reged: 04/16/07
Posts: 215
Loc: Manchester MI
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KEvin,
See if you can e-mail me a reduces size tif of your image. I will run it through GX and you can see what it can do. I would suggest something on the order of 6 meg or so.
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Best Regards
Clay Kessler
www.ssoastro.org
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Tonk
Post Laureate
Reged: 08/19/04
Posts: 4498
Loc: Leeds, UK, 54N
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Is the "GX" tool you refer to actually Russel Croman's GradientXterminator?
And converting RAW to TIFF before calibrating is a distinct NO NO
1. The hot pixels in the RAw are spread out by colour interpolation (debayering) into to neighbouring pixels - wrecks dark calibration. RAWS are not "debayered"
2. The conversion is non-linear unless your software explicily allows this to be overriden. This totally wrecks calibration. RAWS are linear
3. A white balance is applied. If your camera was set to auto white balance the actual WB applied is based on analysing the image content - thus is likely to be different for each frame. RAWS are not WB corrected
So don't do it!
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Televue 85, GM-8/Gemini, Canon 40D (unmodded), Canon 450D (modded w/Astronomiks clip-ins - UV/IR, OWB)
Coronado SM60/BF10, Baader Herschel Wedge
Leeds Sky Clock Ripon Sky Clock
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Cheyenne
super member
Reged: 10/14/05
Posts: 109
Loc: Boulder Co
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Quote:
As for correcting it, the Dynamic Background Extraction tool in PixInsight LE is generally fairly effective on this kind of thing. There are a few tutorials out there on how to use it.
- Gus
Just a quick comment, the PixInsight LE (a free version of a very early version PixInsight) has been removed from distribution by the PixInsight folks, and the licensing agreement associated with PixInsight LE prohibits redistribution. If you already have a copy, it's okay to continue to use it, but you are not allowed to redistribute it.
Part of the reason why PixInsight LE was removed was because it was extremely outdated and people were using it to judge the current full product. Here is a link to the thread on their forum where they announced the removal. PixInsight LE discontinued
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Cheyenne
----
Takahashi TOA-130S / Losmandy G11
Meade 10" f4.5 Newtonian
Homebrew 8" f6 Newtonian
Canon 20Da
ST-4 Autoguider
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1343
Loc: Boston 42° 16' N 71° 08' W
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That announcement was interesting. He's correct that PixInsight LE got mentioned primarily for its DBE tool. I personally found that tool a gateway to LE's other functions, such as the excellent histogram transformation tool.
One thing the announcement tends to overlook is that PixInsight, both Core and LE, is not presented well to new users. If people were using DBE and then downgrading the image for functions that LE could perform, it's because those tools were opaque to new users.
For example, he mentions that LE has color saturation adjustments. I've yet to figure out how to use those either in LE or in the full version (which I own). I've opened up the ColorSaturation process, but I can't make it do what Photoshop will do with a Hue / Saturation layer. So I'm doing he's complaining about - converting to 16 bit so I can adjust saturation in Photoshop.
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
Orion Starshoot Autoguider
QHY8
Philips SPC900NC
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fishonkevin
member
Reged: 04/29/07
Posts: 99
Loc: Michigan
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Hi Folks,
Lots of info heading my way. After reading zAmbonii's and Tonk's post I decided not to convert the raws to tif. I was able to send Clay a 50% re-size of the 32-bit DSS stack and he obtained some very good results using Gradient Exterminator.
I have downloaded the trial version of Gradient Exterminator and will play with the data some more to see what I can get. I am also going to try an Average Combine in the Darkframe Settings of DSS instead of the Median Combine to see if I might get better results.
If any of you would like to take a crack at my data, the 32-bit DSS Stack can be downloaded at Mediafire. Here is the link:
http://www.mediafire.com/?zmmg04yungm
Good Luck and Thanks,
--------------------
Kevin
W.O. ZS 105
Meade AR-5
GM-8
LXD-55
Rebel XT Modified
Quantaray 300mm Mirror Lens, Ziess 135mm, Sigma 24-60mm APO
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