Three Ways to Do Amateur Astrophotography

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Three Ways to Do Amateur Astrophotography

• Photographic Film
• Affordable for beginners, buy film at local
  camera shop
• Hard to master due to development turnaround time
• Commercial CCD Cameras
• Charge-Coupled Device, electronic imaging sensor
  chip
• Much more light sensitive than film
• Immediate feedback, interactive imaging
• Expensive, typically out of range for beginners
• Webcams, best of both worlds!

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Example Webcam Images
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Webcam Facts

• Less expensive than film or commercial CCDs
• Contain image sensors similar to those in
  commercial CCD imagers, though lower quality
• Less light sensitive than commercial CCDs
• The Moon and planets (except Uranus, Neptune and
  Pluto) are bright enough that it is possible to
  image them using a webcam, however
• The smaller the object, the less detail you see
• Faint objects (star clusters, nebulae, galaxies)
  are completely undetectable to unmodified webcams

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Webcam Facts (cont)

• Can make videos, recording hundreds of images in
  a matter of minutes.
• Connect to any laptop or PC via USB port
• Inexpensive, about 50 for models that work well
  for astrophotography

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So webcams are inexpensive and good for making
videos of the Moon

• But,

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Theres More!

• Several free computer programs available on the
  internet make it possible to digitally stack
  multiple images together, making a single,
  quality composite.
• These programs typically contain many other image
  processing features, allowing control of
  contrast, brightness, and frame by frame
  selection.

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Choosing a webcam

• Number of pixels 640x480 is good
• Focus distance
• Cable length
• Price can vary from 10 to 100 nothing fancy
  needed though.
• Philips Vesta Pro works well and is available for
  about 50.

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Attaching a Webcam to a Telescope

• Webcam image sensor must be in focal plane of
  telescope
• Film canister and tape simple, but it works!
• Machined parts work best

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Telescope Mount and Tracking

• Tracking a clock drive counteracts the Earths
  rotation about its axis
• Polar alignment the better the alignment of the
  equatorial mount with the polar axis, the better
  the telescopes tracking is
• Guiding no mount is perfectly aligned, so
  guiding is necessary for long exposures

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Imaging an Object

• Centering object
• Usually easiest to find and center objects with
  an eyepiece first.
• Fine centering can be done prior to focusing
• Focusing
• By far the hardest part
• Find a critical detail to observe while focusing
  back and forth slowly

• Image capture software (usually included with the
  webcam)
• Image capture controls
• Exposure time
• Image resolution
• Frame rate
• Compression settings
• There will inevitably be some image noise (mostly
  thermal)

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Image Processing

• Image stacking
• Combine multiple images to filter out various
  types of noise
• Increase signal to noise ratio
• Requires images be aligned with each other
• Weed out bad frames from videos, improves overall
  image quality in final result
• Image alignment
• Align to highest quality image
• Auto-alignment using software
• Manually align tricky images

• Pixel value scaling operations
• Contrast
• Brightness
• Color correction
• Unsharp masking
• Increases visibility of small details that lack
  contrast
• Strong unsharp mask filtering can make images
  look grainy
• Moderate strength works best
• Many FREE software packages are available for
  this purpose

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Image Processing Examples
50 aligned and stacked images. Image noise is
cancelled out.
Medium strength unsharp mask processing. Brings
out details well.
Strong unsharp mask processing. Brings out
details, but increases graininess.
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Other Astronomical Uses for Webcams

• It is possible to get images of galaxies,
  nebulae, and star clusters by modifying the
  webcam (by soldering and with some circuit
  assembly). Warning Warranty becomes void! ?
• Webcams have been used to monitor light pollution
  (night-sky brightness)
• Occultation timing

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Resources on the web

• http//www.astro.uiuc.edu/uias
• The Univ. of Illinois Astronomical Society, with
  links to our publications on webcam
  astrophotography
• http//www.astrabio.demon.co.uk/QCUIAG/
• (QuickCam and Unconventional Imaging Astronomy
  Group)
• http//www.usno.navy.mil/pao/QuickCamAstro.shtml
• Webcam astrophotos by Geoff Chester, an excellent
  reference and great gallery of images.

• http//home.clara.net/smunch/wintro.htm
• Info on making modifications to webcams for long
  exposures
• http//www.djcash.demon.co.uk/astro/webcam/webcam.
  htm
• More images and info, using the Philips Vesta Pro
  webcam
• http//www.skypub.com
• Sky Telescope magazine, a great place to get
  started in both amateur astronomy and
  astrophotography