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 CREATED
Debayering
the matrix…..
greyscale data
converted to
RGB image
http://www.cambridgeincolour.com/tutorials/camera
-
sensors.htm
P
ROCESSING AFTER
DEMOSIACING
Irreversible 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
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