Observing Projects 11B Uranus and Neptune in the Camera

A well maintained 8-inch telescope with modern coatings and operating under a dark sky can visually reveal stellar objects as faint as magnitude +14.0. Only one of Uranus' moons is actually brighter than that value, but any given telescope can actually photograph objects two full magnitudes fainter than its visual limit, so that 8-inch telescope can actually photograph down to magnitude +16.0.

If you are using film, consider two things. First use the fastest film you possibly can get. Second, store your film in the freezer until you are ready to use it. Freezing the film will push its photographic speed to double what it could do ordinarily. This is important in long-exposure astrophotography because you don't want the exposure to be any longer than it absolutely has to be. There are two reasons for this. First is that every second the shutter is open there is the opportunity for you to make a mistake. Secondly is that reciprocity failure will begin to set in if you leave the shutter open for the kinds of time that it might take to bring out the faint moons of Uranus and Neptune.

The optimized astronomical CCD is far better for this application because of its sensitivity and its speed. Make sure that chip is properly chilled and take progressively longer test images. Experiment with the settings to make sure you can process the noise out of your images and eventually you will begin to reach the level of the faint moons. Also always remember never to give up on a bad image because as your image processing skills at the computer get better, you will be able to pull good signal out of even the noisiest images. And when you're imaging down to magnitude +14, you're going to get a lot of noise.

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