DSLR ASTROPHOTOGRAPHY…. MY WAY MY CAMERA WHY CANON? • Provides RAW files • Not directly useable as an image • “Digital negatives”… unprocessed readout of.
Download ReportTranscript DSLR ASTROPHOTOGRAPHY…. MY WAY MY CAMERA WHY CANON? • Provides RAW files • Not directly useable as an image • “Digital negatives”… unprocessed readout of.
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 ONE SHOT COLOR (BAYER MATRIX) Filtered sensors convert photons to electrons which can be measured http://www.cambridgeincolour.com/tutorials/camera-sensors.htm 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 BRYCE BAYER (1929-2012) http://image-sensors-world.blogspot.com/2012/11/bruce-bayer-died.html 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 • 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)