DSLR_Astrophotograpy..

assoverwroughtΤεχνίτη Νοημοσύνη και Ρομποτική

6 Νοε 2013 (πριν από 3 χρόνια και 5 μήνες)

54 εμφανίσεις

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