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DSLR Astrophotograpy ….. My way. My camera. Why Canon?. Provides RAW files Not directly useable as an image “ Digital negatives”….unprocessed readout of pixels Well suited for dark subtracting and flat fielding…. not true of Nikon - PowerPoint PPT Presentation
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DSLR ASTROPHOTOGRAPY….. MY WAY
MY CAMERA
WHY CANON?
• Provides RAW files• Not directly useable as an image
• “Digital negatives”….unprocessed readout of pixels
• Well suited for dark subtracting and flat fielding…. not true of Nikon
• Canon uses CMOS (complementary metal oxide semiconductor) sensor• Less sensitive than CCD, but cheaper to make
• Generally consume less power than CCDs
• Provide excellent color
ONE SHOT COLOR (BAYER MATRIX)
http://www.cambridgeincolour.com/tutorials/camera-sensors.htm
HOW COLOR IS CREATEDDebayering the matrix….. greyscale data converted to RGB image
http://www.cambridgeincolour.com/tutorials/camera-sensors.htm
PROCESSING AFTER DEMOSIACINGIrreversible process best done on a computer and not in the camera
http://www.cambridgeincolour.com/tutorials/raw-file-format.htm
OTHER REASONS TO USE CANON
• Software readily available
• Acquisition (Images Plus, Backyard EOS, Nebulosity, DigiCamControl
• Processing (Images Plus, PixInsight, Nebulosity, Deep Sky Stacker
• Gain from the experience of others
• Yahoo Group Digital Astro
• Yahoo Group DSLR Astro Image Processing
• Cloudy Nights DSLR & Digital Camera Astro Imaging & Processing
• Jerry Lodriguss CCD books are excellent and website
• Books, adaptors, modifications, etc are widely available
WHY MODIFY THE CANON SENSOR?Stock IR cut filter limits Ha response of sensor
MODIFIED CAMERA IS A MUST
DOWNSIDES OF MODIFYING CAMERA• Must use custom white balance
• Auto mode will not work with custom white balance in older Canons… must use P or M mode
• Canon Warranty is void and they will not service the camera
• Cost is $200 - $300 (Hutech, Hap Griffin, Gary Honis)
COMPARING CANON CAMERAS
APS-C SENSOR (ADVANCED PHOTO SYSTEM)
LENSES AND TELESCOPES THAT I USE
• 17-40mm f/4 Canon
• 85mm f/1.8 Canon (Image scale 13.5 arcsec/pixel)
• 200mm f/2.8 Canon (IS 5.4)
• Borg 77ED refractor, f/5.5 (IS 2.5)
• TAK FSQ 106 refractor, f/5 (IS 2)
• TEC 140 refractor, f/7 (IS 1.1)
CONNECTING TO THE TELESCOPE
IMAGE ACQUISITION• Important to use a computer because it gives the best focus
• Images Plus Camera Control
• Many features….DSLR (Canon and Nikon), CCD, video
• Autofocus control for motorized focusers; temperature compensation
• $240, includes image processing software
• Very good video tutorials
• Backyard EOS
• Only for Canon cameras
• Manual focus aid plus framing aid, drift alignment, video, eclipse mode
• Only $30
BACKYARD EOS FOCUSING
TYPICAL EXPOSURES
• Usually stop down lenses a couple of stops
• Always use ISO1600 (never go below ISO800)
• Always collect RAW images (optional plus JPEG or TIFF)
• Usually 3-4 minute unquided exposures
• Total exposure time usually 1-2 hours (15-30 exposures)
• Dark site is important
IMAGE PROCESSING
• Images Plus
• Dark subtraction
• Debayering conversion to color FITS
• Grading
• File conversion to 16-bit TIFF
• Could do everything in Images Plus
IMAGES PLUS
REGISTAR• Use for aligning and combining (usually)
• Fool proof and very flexible
CCDSTACK• Use for digital development (non linear stretch), creation of luminance image,
deconfolution of luminance
PHOTOSHOP FOR THE REST OF PROCESSING