Astrophotography with webcams

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Astrophotography with webcams
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Astrophotography

• Traditionally done using film or CCD
• Film is typically cheaper than CCD, but there
  trial and error is often involved if you have no
  guidance or prior experience
• CCD is usually too expensive for the budget of a
  typical beginner
• Webcams can be a cheap alternative, providing
  some of the advantages of CCD, but at the cost of
  film

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Webcams for Astrophotography

• Easy to use for one shot color pictures of
  bright objects such as the planets.
• Can record images at higher frame rates than most
  CCDs, can be good for timing astronomical events,
  or imaging fast moving objects
• Inexpensive compared to other options

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Imaging bright objects with unmodified webcams

• Main challenge is to mount the webcam at the
  focus of the telescope
• Many webcams have easily removable lens
  assemblies
• A barrel from a broken eyepiece is perfect, a
  used film canister is workable, but not quite as
  nice
• Tape is your friend, though machining a custom
  mount is best of course

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Finding objects

• Finding planets is easy, they are very bright.
  When defocused a bit, they are VERY easy to
  center in the webcam view
• Finding dim objects can be much harder, in which
  case a parfocal eyepiece or eyepiecebarlow can
  be very handy
• If parfocal eyepieces arent good enough, a flip
  mirror may be necessary.

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Focusing

• Focusing is hard
• Poor seeing can make it even harder
• The CCD chip must be aligned flat in the focal
  plane of the telescope, or images will always be
  partially out of focus
• Tape can also be your enemy it stretches,
  wiggles, expands, and shrinks with temperature,
  thus affecting focus.

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Exposure adjustment compression

• Tricky to set exposure to get both dim and bright
  objects (i.e. Jupiter Moons..)
• Use uncompressed or lossless compression file
  formats for original images, so that you can get
  best processing results later

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Image processing, better pictures

• Adjust brightness
• Increase contrast
• Sharpen images
• Stack multiple images together to get better
  images than any single image
• Pick the best images from a movie, or from a
  sequence of exposures, stack only the best images
  to create a new image

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Modified long-exposure webcams

• Webcams can be modified for long exposures with
  some soldering and careful circuit assembly
• Long exposures are absolutely necessary in order
  to image dim objects
• Still cheaper than buying a commercial CCD
  camera, or even a kit.

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Other uses for astrocams

• Can be used for software-based autoguiding with
  normal CCD or film-based astrophotography
• Measuring light pollution by computer, sky
  brightness, etc.
• If camera mods are non-invasive, can still be a
  webcam! ?