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I'm interested in doing some astrophotography and I'm looking into the equipment needed to get a photo like this: http://www.flickr.com/photos/cscunha1984/6619321531/in/faves-heyvian/

I'm not looking for brands or anything, just the recommendations on what a beginner* should be looking for in a telescope/tracking mount and so on. Would entry level equipment get me the photo above? If not, could you provide an example of what I could expect please?

How would these recommendations differ if I weren't interested in taking photos but just looking? I assume I wouldn't need the tracking mount. I ask because if the photography part makes it too expensive, I would be happy to just look.

*beginner meaning not only someone new to the field but also someone not looking to make a large initial investment.

Vian Esterhuizen
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1 Answers1

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If you prefer to make visual observation only, while some procedures are almost the same, the criteria for a telescope gets easier and the price is lower than with astrophotography. The light gathering of the telescope becomes one of the most important criteria and a dobsonian telescope could be a good choice for that, specially one with at least 6 inches of aperture.

Now, regarding the image: Its resolution is of 12.49 arcsec/pixel, according to http://astrometry.net; the resolution versus the image size and the equipment used to take the picture means that the image was heavily cropped.

The equivalent of that specific resolution is about a 55mm lens in a recent DSLR camera with a 1.6x crop factor. But only a very high quality lens would be able to capture an image like that without visible optical aberrations.

The equipment mentioned by the author in the referred picture is an 80mm aperture / 900mm focal length apochromatic refractor with a 12.3 Megapixels sensor of 23.6mm x 15.8mm and a German equatorial computerized mount. The US current price for that specific equipment is over 2000 USD.

There are a lot of criteria that is relevant in astrophotography, depending on your specific target, the usual criteria for amateur astrophoto includes:

  • Mount: Type, Precision, Periodical error, Stability, tracking past zenith, auto guiding port.
  • Camera capabilities: Resolution, sensor size, light spectra captured, auto guiding capability.
  • Filters: Wide-band, Narrow-band, Color.
  • Telescope design: Severity and type of optical aberrations present, light gathering capabilities, mirror flop, thermal stability.
  • Imaging Software: Alignment type, sub-pixel alignment, hardware requirements.
  • Automation: Image series capture, selection of images, focusing, change of filters.
  • Post processing software: formats supported, hardware requirements.

The specific values for each criteria depend on the specific target of your choosing.

Some of the procedures that are a must to learn:

  • Alignment: Polar alignment, drift method.
  • Levelling: If the mount is not on a permanent pier, should be levelled every time it is moved
  • Focusing: Bathinov mask method, Hartmann mask method, Knife edge method.

And, if your telescope design admits it:

  • Collimation: The alignment of the optical train.
Omar Salinas
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