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Astrophotography with Webcams

Astrophotography with Webcams. John Stone 4/6/2004. 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

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Astrophotography with Webcams

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  1. Astrophotography with Webcams John Stone 4/6/2004

  2. 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

  3. 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 (ISS) • Inexpensive compared to other options

  4. 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, 1” ID copper tube is good, and a used film canister can be made to work, but not quite as stable • Tape is your friend, though making a custom mount is best of course

  5. Mounting with masking tape… • Easiest way to start out, very low-risk • Remove the webcam lens • Tape the unmodified webcam housing to an eyepiece barrel, copper pipe, or film canister • Try it!

  6. Eyepiece barrel mounting works on most scopes… • While not as solid as using T-threads or other more robust mounting schemes, you can very quickly try out the webcam on various telescopes

  7. Finding objects • Having an accurately aligned magnifying finder is very helpful • Finding planets is pretty easy, they are very bright. • When defocused, they are VERY easy to center in the webcam view • Finding dimmer objects is much harder, a parfocal eyepiece can be very handy

  8. Typical field of view… • Field of view of a typical webcam on a 3000mm focal length telescope • If you look carefully you’ll see two moons on the left…

  9. Focusing • Focusing is hard • Poor seeing can make it even harder • Bumping cables will often destroy good focus • The CCD chip must be aligned flat in the focal plane of the telescope, or images will always be partially out of focus • Tape and other flexible construction materials can also be your enemy; they stretch, wiggle, expand, and shrink with temperature, thus affecting focus.

  10. 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 • Experience is the best teacher, every webcam is different, as are different targets

  11. Jupiter… • Short clip taken from my driveway in Urbana during mediocre seeing earlier this week • 2x barlow for 6000mm focal length • Dust mote just to left of center of chip

  12. 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 • Type “astrostack” into Google….

  13. Aligned/Stacked Jupiter(s)… • Processed sequences taken a year ago.. • Eliminated worst frames, aligned and stacked remaining frames with Astrostack • Taken with an 8” SCT & 2x barlow (4000mm focal length)

  14. Aligned/Stacked Saturn(s)… • Top image taken using UI 12” refractor, 4500mm focal length • Bottom image taken with 8” SCT /w 2x barlow, 4000mm focal length

  15. Modified long-exposure webcams • Webcams can be modified for long exposures with some soldering and careful circuit assembly – people call these modified cameras “Astrocams” • Long exposures are absolutely necessary in order to image dim objects • Still cheaper than buying a commercial CCD camera, or even a kit. • Quality is limited by noise, 8-bit readout, but still a fun way to get started

  16. 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! 

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