Transcript Front Yard CCD Astrophotography

Front Yard CCD
Astrophotography
January 11, 2007
My Recommendations for starting
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Learn!
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Purchase/read “The New CCD Astronomy” by Ron Wodaski
Purchase/read “Photoshop for Astrophotographers” by Jerry
Lodriguss
SBIG users group
Websites:
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http://www.rc-astro.com/ (Russell Croman)
http://www.robgendlerastropics.com/ (Robert Gendler)
http://www.mistisoftware.com/astronomy/ (Jim Misti)
Club expert/mentor (John Boudreau)
Webcam and planets/moon
What can I do?
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Start: Photographs of the moon and planets
Webcam
 Registax
 Good scope
 Moderate tracking ability
 Works from light polluted areas (bright objects)
 Good results with minimal investment obtained
from stacking hundreds of images
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What can I do?
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Deep-sky objects from Andover
Light pollution effects photograph quality (increased
sky background noise )
 Long exposure times >5 hours/object
 Practical implications of seeing conditions
 Good to high level quality equipment produce better
quality photos (expense/investment)
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Produce good quality photographs
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Digital Development Processing algorithms (DDP)
and photo-processing “workflows” can correct many
problems
Deep Sky CCD – Mount Selection
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Spend 60% of money on
Mount
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Periodic error correction
(PEC)
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30 sec exposure less
important
30 min exposure requires
good PEC and tracking
(auto guiding)
Telescope focal length
significant factor
Accurate auto-guiding
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Worm-gear design
Motor design
Deep Sky-Mount Suggestions
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I use Astro-Physics 900 GTO
Mounts others have used
Losmandy (G11 and Titan)
 Takahashi
 Paramount
 Mountain Instruments
 Meade (RX400, LX200)
 Celestron (CGE)
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Learn characteristics of your mountAuto-guiding
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Balance
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“Slight” east weighting
Appropriate selection of
weights to center moment
arms
Adjust worm gear /
mesh
Software or mount
firmware PEC correction
Deep Sky CCD – Telescope Focal Length (ref: “The
New CCD Astronomy”)
Length
Seeing
Aperture Targets Flexibility
400-800
Rarely
3-6”
Big targets
Good-add
Barlow
800-1500
A
consideration
5-10”
More
targets
Good if focal
reducers
available
15002000
Always
matters
8-16”
Many
more
targets
Good if focal
reducers
available
Deep Sky – Telescope Selection
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Better optical quality provides sharp correct color
round stars
Recommend match telescope with CCD camera (ref:
http://www.sbig.com/sbwhtmls/online.htm)
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Telescope Field of View
CCD chip size
CCD chip pixel size
Flat field needed
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Adapter for telescope (field flattener)
Optical design with flat field (modified Petzval)
Astro-Physics sells adapter for SBIG cameras that fits in front of
camera (http://www.astro-physics.com/ -CCD Telecompressor (CCDT67))
My Deep Sky Telescope Selection
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Takahashi FSQ 106 N
APO fluorite refractor
Modified Petzval - 88mm
circle flat field image
4” focuser
3600 camera angle adjuster
Aperture 106mm
Focal length 530mm
Compatible with large CCD
chips currently on market
Modified Petzval Design
Deep Sky-CCD Camera Selection
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Anti-Blooming Gate (ABG)
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Non-Anti-Blooming Gate (NABG)
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Easier to use
Less sensitive
More sensitive
Careful planning of exposure time
needed (experience)
Minor blooming can be fixed
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Software
Photo Processing takes more time
Camera Designs
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One-shot color camera
Filters located on chip – no filter wheel
 Easy to use –good example is planets via webcam
 Less flexible
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Black and white with filter wheel
Flexible – can use many different types of filters
 More complex to photo-process to color image
 Better control over quality and composition of color
image
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Match Camera, Telescope and
Mount
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Telescope focal length (ref:
http://www.sbig.com/sbwhtmls/online.htm)
Ability of mount to track and guide effectively
Compensate for longer exposure times needed for
ABG
 NABG better if short exposure times are needed to
match mount capability
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Light pollution-NABG offers advantage
Auto-guiding options
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Separate CCD and scope
for guiding
Camera with built-in
guide chip (Santa Barbara
Instrument Group, Inc
(SBIG))
Don’t guide
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Webcam
Short exposures (30 sec)
and stack 50 – 200 images
Improve signal to noise
My Camera Selection SBIG ST2000XM (ref: SBIG website)
CCD
Kodak KAI-2001M +
CCD
TI TC-237
Pixel Array 1600 x 1200 pixels
CCD Size 11.8 x 8.9 mm
Total Pixels 2 million
Pixel Size 7.4 x 7.4 microns square
~45,000 e- unbinned
Full Well Capacity
~90,000 e- binned
Dark Current 2.5e-/pixel/sec at 0 deg. C.
Antiblooming Standard
Readout Specifications
Shutter Electromechanical
Exposure 0.001 to 3600 seconds
Correlated Double Sampling Yes
A/D Converter 16 bits
A/D Gain 0.18e-/ADU unbinned
Read Noise 13.5e- rms
Binning Modes 1 x 1, 2 x 2, 3 x 3
Pixel Digitization Rate ~ 425kps
Full Frame Download ~ 4.5 seconds
My Camera Selection SBIG ST2000XM (ref: SBIG website)
My Camera Selection SBIG ST2000XM
My Camera Selection SBIG ST-2000XM
Photo Session-Focus
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Maxim DL Software
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View of star size and
number of small faint
stars
Optimize for maximum
intensity for star (signal)
Optimize for Full Width
at Half Maximum
(FWHM)
Focus Zen-Maxim DL
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Gross focus with imaging chip at 2 bin
Fine focus small selected area of CCD at full resolution
1bin
Set exposure time at >2 sec so that changes in seeing
are not major factor
Watch temperature
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FSQ in focus range is 35 microns
Temperature change >20F causes stars to bloat and loss in
signal
Focus-aid: Plan to purchase Robo-Focus
Photo Session – Object
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Study object
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Size (mosaic will need to be planned)
Color
Brightness
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Filter selection
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Globular cluster uniform
Galaxy Bright core faint outer region
Nebula have strong narrow band emissions
Luminance for white light detail (L)
Red, Blue, Green (RGB) for color
Halpha (656.26 nm) narrow band filter for red nebula
Narrow band filter composites
Match filters to object and combine (LRGB, RRGB,
HalphaGB, LHalphaRGB)
Photo Session – Frame and Lock
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Locate object
Roughly frame object on image chip
Find suitable guide-star (>25000 ADU for filter
transmitting lowest signal – Halpha)
Finalize object framing
Lock on guide star
Auto-guide
Photo Session-CCD Camera
Correction Frames
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Dark Frames. Correct
for dark current that
increases as a function of
time and temperature
(Thermal signal)
Bias Frames. Bias that
occurs when pixel is read
by camera (Zero light
exposure)
Photo Session – Flat Field
Correction for Optics
Taking Flat Field Frames