This website and all images are Copyright (C) 2005 by Timothy Cann Solutions and Oceanside Photo and Telescope, all rights reserved.
Deep-Sky Images taken with the Canon 20Da (+ one using an SBIG STL-11000)
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Let's go back to the image of the M20 & M8 region to look again at the image taken under ideal conditions:
Date: June 17, 2005; Object: M8 and M20; Camera: Canon 20Da; Telescope: Takahashi FSQ-106; Mount: Losmandy G11 Gemini; Guider: STV e-Finder; Exposure: 300 Seconds, ISO800, NR=Off; Taken by: Eric Blackhurst & Chriss Hoffman of OPT; Additional processing using ImagesPlus v2.5: Digital Development Auto, Background - Contrast - Stretch, Color Adjustment | Saturation - Brightness
If you've been watching, this image is different from the one presented on the 20Da home page. It's the same picture, but it's been processed using ImagesPlus to bring out more of the nebulosity present in this rich region of the Milky Way. Let's compare this to another image:
Date: June, 2005; Object: M8 & M20 region; Camera: SBIG STL-11000; Telescope: Takahashi FSQ-106; Guider: SBIG STL-11000; Exposure: 4,800 seconds each for Red, Green and Blue filters; Processing: PhotoShop CS; Taken by: Bill Patterson.
See: http://www.laastro.com/M8-M20-Widefield_spec.html for more details and the uncropped image.
Bill's image is clearly superior. There is much more detail in the red regions, the colors are more vibrant and clear. There's more color in some of the fainter areas. This image was taken using a cooled astronomical camera that costs four times as much as the 20Da. And let's look again at the exposure time. Three filters at 80 minutes each, that's 4 hours of exposure time. (The 20Da image was a single 5 minute exposure.) The original image was also 50% larger. My cropping made the field of view the same as the 20Da image. Thank you Bill for allowing me to use your wonderful image.
Now let's do something completely different. Here's my image of M27:
Date: June 19, 2005; Object: M27; Camera: Canon 20Da; Telescope: Takahashi CN-212 f/12.4; Mount: Paramount ME; Guider: NO GUIDING; Processing: ImagesPlus v2.5; Exposure: 3-210 second exposures, Digital Development Auto, Adaptive Add, ISO800, NR=On; Taken by: Tim Cann
Here's the same object imaged through three narrowband filters, Astrodon 6nm H-alpha, SII and OIII filters. (See "Narrowband Imaging in Color" by Richard Crisp in the August 2005 Sky & Telescope.) This is a rather unconventional thing to do: use narrowband filters with a color DSLR:
Date: June 30, 2005; Object: M27; Camera: Canon 20Da; Filter wheel: Optec IFW with Astrodon 6nm SII, H-alpha & OIII; Telescope: Takahashi CN-212 f/12.4; Mount: Paramount ME; Guider: STV w/105mm f/2.8 camera lens; Processing: ImagesPlus v2.5; Exposure: 1-900 second exposures (each filter), ISO1600, NR=On; Processing: ImagesPlus v2.5, Split Colors - LRGB, Save each color as monochrome, Combine LRGB | Scale 1.0 each color, Color mapping: SII=Red, H-a=Green, OIII=Blue, Digital Development Auto, Adaptive Add, Background - Contrast - Stretch, Color Adjustment | Saturation - Brightness; Taken by: Tim Cann
This image uses the Hubble color maping referred to in Richard Crisp's article.
Now, let's look at two images of objects that, at the respective exposure times at least, might be said to be outside the limits of the 20Da:
Date: July 1, 2005; Object: IC5050 the Pelican Nebula; Camera: Canon 20Da; Telescope: Takahashi FSQ-106 f/5; Mount: Takahashi EM-200 Temma; Guider: STV e-finder; Processing: ImagesPlus v2.5; Exposure: 10-300 second exposures, Digital Development Auto, Adaptive Add, ISO800, NR=Off, averaged dark calibration. Taken by: Tim Cann
Date: July 1, 2005; Object: NGC6960 the Veil Nebula; Camera: Canon 20Da; Telescope: Takahashi FSQ-106 f/5; Mount: Takahashi EM-200 Temma; Guider: STV e-finder; Processing: ImagesPlus v2.5; Exposure: 20-300 second exposures, Digital Development Auto, Adaptive Add, ISO800, NR=Off, averaged dark calibration. Taken by: Tim Cann
You decide for yourself. The image of the Pelican is clearly underexposed at 3,000 seconds. I'd liked to have had the time to go back and do it for two or three times that. The Veil on the other hand, though underexposed, contains much more detail. Again, two or three times the exposure time would undoubtly reveal more detail and produce more color depth.
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Tim