dslr astrophotography …. my way

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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 - PowerPoint PPT Presentation


DSLR Astrophotograpy.. My way

DSLR AstrophotograpHy. My way

My camera

Why Canon?Provides RAW filesNot directly useable as an imageDigital negatives unprocessed readout of pixelsWell suited for dark subtracting and flat fielding not true of Nikon

Canon uses CMOS (complementary metal oxide semiconductor) sensorLess sensitive than CCD, but cheaper to makeGenerally consumes less power than CCDsProvides excellent color

Creating a color digital image

One shot color (Bayer Matrix)http://www.cambridgeincolour.com/tutorials/camera-sensors.htm

Filtered sensors convert photons to electrons which can be measured Bryce Bayer (1929-2012)

http://image-sensors-world.blogspot.com/2012/11/bruce-bayer-died.htmlHow color is createdDebayering the matrix greyscale data converted to RGB image

Each pixel contributes to the luminance image which gives detailhttp://www.cambridgeincolour.com/tutorials/camera-sensors.htm

Processing after demosaIcingIrreversible processes best done on a computer and not in the camera


Other reasons to use CanonSoftware readily availableAcquisition (Images Plus, Backyard EOS, Nebulosity, DigiCamControl)Processing (Images Plus, PixInsight, Nebulosity, Deep Sky Stacker)Gain from the experience of othersYahoo Group Digital AstroYahoo Group DSLR Astro Image ProcessingCloudy Nights DSLR & Digital Camera Astro Imaging & ProcessingJerry Lodriguss CCD books are excellent and websiteBooks, 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 cameraMust use custom white balance

Auto mode will not work with custom white balance in older Canons must use P or M modeCanon warranty is void and they will not service the cameraCost is $200 - $300 (Hutech, Hap Griffin, Gary Honis)

Comparing Canon Cameras

APS-C sensor (advanced photo system)

Lenses and telescopes that I use17-40mm f/4 Canon85mm 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 acquisitionImportant to use a computer because it gives the best focusImages Plus Camera ControlMany features DSLR (Canon and Nikon), CCD, videoAutofocus control for motorized focusers; temperature compensation$240, includes image processing softwareVery good video tutorialsBackyard EOSOnly for Canon camerasManual focus aid plus framing aid, drift alignment, video, eclipse modeOnly $30

Backyard EOS focusing

Typical exposuresUsually stop down lenses a couple of stopsAlways use ISO1600 (never go below ISO800)Always collect RAW images (optional JPEG or TIFF)Usually 3-4 minute unguided exposuresTotal exposure time usually 1-2 hours (15-30 exposures)Usually take 5-10 dark exposures, but no flats

Image processingImages PlusDark subtraction to reduce sensor noise (no flats)Debayering conversion to color FITSGradingFile conversion to 16-bit TIFFCould do everything in Images PlusRegistarUse for aligning and combining (usually median)Fool-proof and very flexible; mosaics; aligning different formats

CCDStackUse for digital development (non-linear stretch)Creation of luminance imageDeconvolution of luminance

PHOTOSHOP (CS5)Use LRGB method (Adam Block)Carbonis Astronomy Tools, Gradient Xterminator, Noise Ninja, HLVG

Monitor calibrationImportant if others are looking at your images onlineSpyder4 Express (~$100)

Slides on websitewww.geoandpat.com


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