lawrie
Carpal Tunnel
Reged: 01/31/06
Posts: 1743
Loc: Okanagan Valley
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Hi all,
I am in the middle of reading Photoshop Astronomy, and Jerry's CD Photoshop for Astrophotographers.
The techniques setting black and white points are great, and just using the numbers takes out second guessing.
The only issue is, they have you starting on a well defined/ stretched image,to place your points, I don't know about you guys (girls) but when I have finished registering and stacked images, the result is quite dark. Needs a bit of stretching to bring out anything. It would be easy if my images looked that bright right after stacking.
So do you do this stretching first, then set your black and white points, then use curves again to bring out the highlights?
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Clear Skies
Lawrie
Ultima 8
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DSI Pro - Pro II
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Footbag
sage
Reged: 04/13/09
Posts: 465
Loc: Scranton, PA
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After changing the mode, I usually go to levels and click auto. Even if I chose not to go with the results, it gives me an idea of where the darker, lighter and nebulous areas of the image are.
From there, you can click cancel and then try your levels all over again. Usually using auto will blow out and clip a lot of the image, but at least it lets you see what is there.
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Adam
Celestron CPC 800, Celestron HD Wedge
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Alex McConahay
super member
Reged: 08/11/08
Posts: 130
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It is iterative.
Pull up a histogram, and if you have gaps on either end, pull your sliders to where the gap ends. (If you have no gaps, you have none to get rid of before stretching.)
Then do a stretch, and check/adjust levels again.
Then do another stretch, and levels, etc. Go from one to another.
One of my buddies who is real good does a few gamma adjustments, moving the middle slider down to the top of where the hump ends. Then sets the black/white sliders.
Alex
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bryansay
super member
Reged: 02/25/09
Posts: 111
Loc: Georgetown, TX
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I recall that Jerry recommended setting the white and black points in each channel in "PS for AP". This helps with
White balance He first did a Threshold left and right to identify the lightest and darkest point on the picture to set the measurement points.
In "A guide to AP with DSLR" he suggested using a picture of a macbeth card (or white paper) in broad daylight and then use those values to white balance.
This weekend I tried the second method with a 16% graycard ($4 at local camera shop). In Images Plus I did a white balance on the daylight graycard and then applied those settings to my stacked image. I then proceed to set black and white points in RGB leaving room at both ends for subsequent stretching.
I got my best results yet by far. Give it a try with regular paper first. (Make sure that it is bright sunshine. My first attempt was in cool morning sun and did not have the desired results)
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Bryan Sayler
Celestron C9.25; Orion ED80
HEQ-5; Orion ST-80 w/starshoot
Nikon D80; Canon 40D Hap Griffin Mod
Empty Wallet 
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David Rosenthal
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Reged: 06/23/06
Posts: 1645
Loc: NJ
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Lawrie,
I use one of two methods for my "initial stretch":
1. For high SNR Stacks I will use Maxim DL's DDP
2. For Lower SNR stacks, I will perform Itterative aggressive curves in PSCS until the detail starts to show.
Then I will use R. Scott's "By The Numbers" method for B&W points.
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David Rosenthal | Midland Park, NJ
My Image Gallery
http://www.EastCoastAstro.com
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lawrie
Carpal Tunnel
Reged: 01/31/06
Posts: 1743
Loc: Okanagan Valley
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Thanks guys, That was what I was wondering about, do an initial stretch to bring out some detail then use the by the numbers method.
David how are determining the SNR to know the values?
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Clear Skies
Lawrie
Ultima 8
Atlas EQ-G
ZenithStar 80 FD
DSI Pro - Pro II
Canon 350D
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David Rosenthal
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Reged: 06/23/06
Posts: 1645
Loc: NJ
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Lawrie.....there are 2 methods for that..one more scientific than the other.
You can use the Maxim DL Information Window with a large aperature sampl and look at the numbers. Or, as I do sometimes, try DDP, if it looks poor, bag it and do the stretching in PSCS!!!
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David Rosenthal | Midland Park, NJ
My Image Gallery
http://www.EastCoastAstro.com
Atlas EQ-G EQMOD USBDIR [Self-Hypertuned]
8" Meade SCT | Borg 76ED | Takahashi FS-60C
Self Modded 400D | SX MX716 | DSI Pro | SPC900NC
Series 5000 26mm, Hyperion 17mm, TV 11mm Plossl
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Nils_Lars
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Reged: 01/04/08
Posts: 3431
Loc: Santa Cruz Mountains , CA
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I do the same as David , DDP first and then if not curves in PS CS2.
I will do curves after DDP anyway it just seems to give me a good starting place to set the RGB black points and give an even color.
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Erik
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lawrie
Carpal Tunnel
Reged: 01/31/06
Posts: 1743
Loc: Okanagan Valley
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Ok, use DDP to stretch the initial good to know, thanks.
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Clear Skies
Lawrie
Ultima 8
Atlas EQ-G
ZenithStar 80 FD
DSI Pro - Pro II
Canon 350D
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David Rosenthal
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Reged: 06/23/06
Posts: 1645
Loc: NJ
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Just be careful not to be to agressive with it. I use Auto for both parts in Maxim DL, then uncheck the left auto option and back down the number until there is a comfortable gap on the left side of the histogram. This makes sure there is room for a proper black point setting in PSCS.
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David Rosenthal | Midland Park, NJ
My Image Gallery
http://www.EastCoastAstro.com
Atlas EQ-G EQMOD USBDIR [Self-Hypertuned]
8" Meade SCT | Borg 76ED | Takahashi FS-60C
Self Modded 400D | SX MX716 | DSI Pro | SPC900NC
Series 5000 26mm, Hyperion 17mm, TV 11mm Plossl
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Buhlig
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Reged: 12/03/07
Posts: 193
Loc: Derby, KS
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Can you point me to these resources on tutorials? I had the post on photoshop for M33 and would like to read up on how to use it (just in case I decide to get it)....which I most likely will.
Sean
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http://www.flickr.com/photos/derbysluggers/sets/72157605255114566/
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Nils_Lars
Post Laureate
Reged: 01/04/08
Posts: 3431
Loc: Santa Cruz Mountains , CA
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Oh and Nebulosity is what I use for my DDP and it is a lot cheaper , MaximDL is a great program also with a lot of other features.
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Erik
Orion Atlas Self Hypertuned (EQMOD)
Orion ED 80
Williams Optics VII reducer
Celestron 8" SCT
Orion Starshoot Autoguider
PHD guide
Canon 400D Hap Griffin Mod w/Baader filter
Astronomik clip-in LP filter and 12nm Ha
Stilleto CVF and Bahtinov mask
Tamron 75-300mm&28-80mm lenses
NexImage webcam
http://www.flickr.com/photos/31986095@N05/
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guyroch
sage
Reged: 01/22/08
Posts: 255
Loc: Ottawa, Canada
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Quote:
Oh and Nebulosity is what I use for my DDP and it is a lot cheaper , MaximDL is a great program also with a lot of other features.
Same here, Nebulosity is a steal at $60. DDP does not work all the time, but when does... oh boy does it ever work!
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Skywatcher 750mm 6" Reflector f/5
Celestron CG5-GT mount
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Bushnell 8x42 h2o® Waterproof Binoculars
Sky Atlas 2000.0 Field Version (Laminated)
Plenty of patience and a wife that doesn’t quite understand my love for clear skies, but let’s me go out anyway ~ thanks honey bunny 
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lawrie
Carpal Tunnel
Reged: 01/31/06
Posts: 1743
Loc: Okanagan Valley
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Sean,
here's Jerry's site
http://www.astropix.com/
The other book we are talking about is R. Scott Ireland
its called Photoshop Astronomy
http://www.willbell.com/ccd/index.htm
Hope this is what you were looking for.
Thanks again guys, I have Maxim and will try with it.
Hopefully the weather will change and I can see if the Hypertune I gave the mount worked.
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Clear Skies
Lawrie
Ultima 8
Atlas EQ-G
ZenithStar 80 FD
DSI Pro - Pro II
Canon 350D
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