Some Tips and Some Traps

From this point on, past experience of using CCDs helps enormously. After you have studied several hundred images, it is possible to get to know your camera pretty intimately. You recognize where on the chip there are likely to be hot pixels and blemishes and how it will perform in various sky conditions. Variations in transparency can be the greatest. Surprisingly, and up to a point, small amounts of mist can assist in achieving fainter magnitudes. The increased stability that it causes results in pinpoint stars, concentrating the starlight on a smaller area of the chip. Hot pixels regularly appear. Knowledge of the chip temperature and a pixel's location can often allow you to eliminate it as a supernova candidate. With three cameras this becomes increasingly difficult. The usual clue to the existence of a hot pixel is the lack of a point-spread function (PSF). Moving the histogram settings should cause a true PSF to increase and decrease in diameter. You should nevertheless be aware that true stars can look very pixular on those very good nights. Stars falling on gaps between pixels can also have odd appearances. Elimination as early as possible in the process is the key to success. This is because even after a candidate is suspected, a lot of checking is required. Your most valuable asset is telescope time under suitable skies. I do all other checks before I consider stopping a running script to test for a suspect. An excep-

Figure 12.8. Tom Boles with two Paramounts in the roll-off roof observatory.

tion to this might be if it were brighter than magnitude 15 and very far from the ecliptic. This leads nicely into a list of checks and the process that I routinely make.

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Digital Camera and Digital Photography

Digital Camera and Digital Photography

Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.

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