Last updated
June 15, 2005
CCD IMAGE PROCESSING
Order of Operations
for those who are concrete / sequential
( like myself )
Images were acquired using CCDOPSW (Windows 95 version) by SBIG (Santa Barbara Instrument Group)
Processing was done with CCDOPSW, CCDSharp, CCDSoft (Software Bisque), and Adobe ImageStyler
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| Step 1: Open the image file to be processed using CCDOPS, CCDSoft, or another image processing program of your preference. This is a "raw" image of a +12.0 magnitude galactic cluster NGC 2158 in Gemini using an SBIG ST-7 at prime focus of a Meade 10" f/6.3 LX 200 in self-guide tracking mode with an integration time of 180 seconds at -25 degrees Celsius. The field of view is approximately 15 X 10 arc minutes. Resolution is 768 X 512 pixels. No filtration was used. | Step 2: Take a "darkframe" exposure of the same duration (in this case 180 seconds) and at the same temperature as the original image with the dewcap on. Notice that the "thermal noise" is just about the same saturation as the original and flatfielded images. Then subtract the "darkframe" from the original image and save it under a different filename earlier. |
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| Step 3: Take a "flat-field" image, dark subtract it, and save it with a new filename. This is a 3 second "flat field" exposure (at the same temperature) taken of a 30" X 36" white foamcore board using two small 12" X 18" white boards illuminated by 25 watt floodlights to relect light back onto the larger white board at 45 degree angles on either side of the telescope (visit my OBSERVATORY page to see the setup). | Step 4: Divide the original "raw" image by the dark-subtracted flat-field image. Notice that the dark round area near the center of the field of view (which I believe is caused by the secondary mirror obstruction inherent in SCT's) and several "dust-doughnuts" have been removed. Save the image under a new name like NGC 2158 dark-flat fielded. |
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| Step 5: Remove any "hot" and "cold" pixels at this point and save the image as a different filename like NGC 2158 rough processed. Don't adjust the "background" and "range" (brightness and contrast) YET if you plan to do a L-R (Lucy-Richardson) deconvolution. If you don't have CCDSharp or another program that has this feature then go ahead and adjust them. | Step 6: Import the image into CCDSharp. Mark a number of stars with the centroid tool or use the "box" tool to drag over an area of concern. Select a number of iterations (I used three).Click on the "GO" button to begin a L-R (Lucy Richardson) deconvolution. When the process is finished, examine the stars. If the stars appear to have "black holes" in the center of them, you used too high a number of iterations. Simply redo it using a lower number. When you are satisfied, adjust the "background" and "range" parameters. Save the image with a different filename and format of your choice (.tif, .fits, .jpg, etc.) for importing into your favorite graphics program (Photoshop, ImageStyler, etc.) for any final tweaking that you may want to do. |
Digital Development (DDP)
with
vs.
LR (Lucy-Richardson deconvolution)
with
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| 30 second "raw" image of M 13 captured with ST-7 | Dark subtracted/flat fielded with hot & cold pixels removed using CCDOPS only |
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| Same raw image processed entirely with StellaImage2 using DDP | Same StellaImage2 with 2 iterations of LR using CCDSharp |
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| RGB color image of M13 using CCDOPS and CCDSoft | LRGB image of M13 processed with StellaImage2 exclusively |
CCD Planetary Imaging
with LX200 10" f/6.3
and
SBIG ST-7/CFW-8
using 18mm orthoscopic eyepiece projection
working at 4800mm f/18.9
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| LRGB image of Jupiter combining the best of 3 luminance images with the best of each R, G, & B images from 30 (.12 - .18s) exposures of each. Each frame was first dark subtracted and levels set. Only color, brightness, and contrast were adjusted after the luminance and RGB images were combined. | This is also an LRGB image made from the same data set of images but each of the luminance frames and RGB frames were sharpened using Unsharp Mask before they were combined as well as the dark frames subtracted and levels set. Brightness, color correction, and contrast were set after being combined |
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