CCD Imaging and Processing 0 .0 2 Aschen 3.1 Alan Chen CFAS St ar - - PowerPoint PPT Presentation

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CCD Imaging and Processing

Alan Chen CFAS St ar Part y 20 0 2

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CCD Imaging and Processing

The camera Mat ching scope wit h camera Taking t he image Processing t he image Final result s

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The Camera

• Choosing t he camera

Many different opt ions t o st art imaging wit h

Digit al camera - easiest way t o st art

• Nikon CP9 9 5
• Olympus C-series
• Full digit al SLR

Webcam - excellent for planet s (check QCUIAG)

• True CCD version (not CMOS based)

» Philips Toucam Pro, Vest a Pro » Older Logit ech/Connect ix B&W Quickcam

Video camera - I.e. St ellaCam - semi-deepsky capable True CCD camera for ast ro-imaging

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The Camera

• True CCD camera

Several major CCD camera vendors

SBIG - probably t he largest and most recognizable Apogee - high end cameras FLI - high end cameras St arlight Express - great values SAC - very inexpensive t o st art wit h - lacking soft ware

support

All are good choices

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The Camera

• St arlight Express

MX7C - why is t his a good choice?

An excellent first camera

• Good for st art ers and advanced imagers
• Relat ively simple t o operat e, especially for color images

Affordable by CCD st andards

• 750 x58 2 resolut ion t ops in it s price range

Small and compact - 2” dia Light weight

• Balance kit not necessary for t he LX20 0
• Approximat ely t he weight of a good 2” eyepiece

Primary SBIG equivalent considered - ST-7E

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The Camera

• St arlight Express

MX7C (cont .)

One shot camera - color mat rix filt ers - CMY

• Synt hesizes RGB from t he filt ered signals
• Much less overall imaging t ime involved for color

» Color filt er wheel not required

• Probably not as accurat e a color balance as RGB imaging

Self-guiding capabilit y wit h St ar20 0 0 int erface

• Uses t he same chip for imaging and guiding
• Sensit ivit y reduced by 50 %

as a result

• Simple soft ware int erface t o self-guide

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Mat ching Scope and Camera

• General guidelines

Sampling

Depends on seeing

• Good seeing (i.e. 1

are-sec) can t olerat e higher resolut ion sampling rat es

• Sampling rat e (arc-sec/pixel) = 20 6 x (pixel size)/(focal

lengt h) » Pixel size is dependent on t he camera » FL can be varied by focal reducers and barlow lenses

• Scope and camera should provide a t ypical sampling rat e of

approximat ely 2 arc-sec/pixel » 1 2”LX20 0 @ f/3.3 = 1 .7 arc-sec/pixel (good mat ch!) » Rat es>2 is undersampling and rat es<2 is oversamplign

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Taking t he Image

• Imaging process

Set up t he opt ics/camera

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Taking t he Image

• Imaging process

Set up scope, camera, lapt op and align

No hot plugging - t urn everyt hing on aft er set up

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Taking t he Image

• Imaging process

Choose first object Slew t o it using HPP

HPP t arget s a nearby bright st ar t o cent er Use t his opport unit y t o focus CCD camera on st ar Slew t o object

Not e: Ast roart is referenced in t his present at ion

• Great support for St arlight cameras
• Relat ively inexpensive (~$1

50 ) » Handles bot h camera cont rol and image processing

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Taking t he Image

Take a quick 5 t o 3 0 second image of t he object

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Taking t he Image

Select a st ar anywhere on t he image t o fine focus

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Taking t he Image

• Select t he focus box - st ar is rough focused

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Taking t he Image

• Good focus has been achieved

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Taking t he Image

• Aut oguider set up

Example uses a video

camera as t he guider

Mint ron 1

2V1 (0 .0 0 0 1 lux)

St ar20 0 0 equally effect ive Scope set up

Correct ion speed Correct ion range Backlash

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Taking t he Image

• Taking t he image

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Taking t he Image

• To t ake t he

image, select image or sequence

Image

generat es a single image

Sequence allows

mult iple images t o be t aken and saved

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Processing t he image

• Ast roart : bat ch processing menu
• For t he MX7C

camera, t he Ant i- aliasing set t ing can be increased t o minimize t he point source issue for

• ne-shot cameras,

eliminat ing t he

• ccassional wild

st ar color

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Processing t he image

• Bat ch processing: select ing t he images

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Processing t he image

• Bat ch processing: result s in LRGB separat ion

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Processing t he image

• Pre-processing: select ing st ars t o aut oalign

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Processing t he image

• Pre-processing: select files t o combine

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Processing t he image

• Pre-processing: 30 x2min. images combined

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Processing t he image

• DDP processing - compresses signal range

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Processing t he image

• DDP processing - result of ddp filt er

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Processing t he image

• Unsharp Mask filt ering

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Processing t he image

• Unsharp Mask filt ering

Sharpens t he fine

nebulosit y and t ight ens t he st ar images

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Processing t he image

• St ret ching t he image wit h a hist ogram

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Processing t he image

• Color processing

Repeat t he procedure as in slide 22 t o combine all

• f t he R-frames t oget her, t hen t he G-frames and

finally t he B-frames

Upon complet ion, t here should be one L, R, G and

B frame (4 t ot al frames)

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Processing t he image

• Color processing

Trichromy command We have color!

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Processing t he image

• Color processing

Tweaking colors Sliders at t he far

right t o adjust color int ensit y and balance

Hist ograms can

also be employed for bet t er cont rol

Linear st ret ch

preferred for color frames

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Processing t he image

• Color processing - final result : saved as a jpg

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Processing t he image

• Color processing - t weaking in Corel Phot opaint

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Processing t he image

• Corel Phot o - resampling t o square t he pixels

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Processing t he image

• Corel Phot o - Eliminat ing image defect s

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Processing t he image

• Corel Phot o - Using t he clone t ool

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Processing t he image

• Corel Phot o - Gaussian blur

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Processing t he image

• Corel Phot o - save wit h compression - Done!

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M42: 8 0 mm St ellarvue