DSLR AstrophotograpHy…. 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 consumes less power than CCDs Provides excellent color

Creating a color digital image

One shot color (Bayer Matrix) Filtered sensors convert photons to electrons which can be measured http://www.cambridgeincolour.com/tutorials/camera-sensors.htm

Bryce Bayer (1929-2012) http://image-sensors-world.blogspot.com/2012/11/bruce-bayer-died.html

How color is created Debayering the matrix… greyscale data converted to RGB image Each pixel contributes to the luminance image which gives detail http://www.cambridgeincolour.com/tutorials/camera-sensors.htm

Processing after demosaIcing Irreversible processes 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) Importance of image scale… try to stay >2

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 JPEG or TIFF) Usually 3-4 minute unguided exposures Total exposure time usually 1-2 hours (15-30 exposures) Usually take 5-10 dark exposures, but no flats

Image processing Images Plus Dark subtraction to reduce sensor noise (no flats) Debayering conversion to color FITS Grading File conversion to 16-bit TIFF Could do everything in Images Plus

Registar CCDStack PHOTOSHOP (CS5) Use for aligning and combining (usually median) Fool-proof and very flexible; mosaics; aligning different formats CCDStack Use for digital development (non-linear stretch) Creation of luminance image Deconvolution of luminance PHOTOSHOP (CS5) Use LRGB method (Adam Block) Carboni’s Astronomy Tools, Gradient Xterminator, Noise Ninja, HLVG

Monitor calibration Important if others are looking at your images online Spyder4 Express (~$100)

Slides on website www.geoandpat.com