Beware of impostors!
If you find a suspected nova, look closely at the star image. Does it look "fuzzy" like the other stars, or does it look boxy or very sharp? If it's not fuzzy, it's probably an artifact, rather than a nova. Sometimes cosmic rays hit the detector, and make small, sharp spots that can be mistaken for stars. Look for evidence that the suspect is an impostor (artifact) instead of a nova. Some of the images contain artificial features or "bad pixels" from the CCD camera. They appear as sharp black rectangles or squares in the images. Nova candidates are fuzzy, not sharp.
Examples of artifacts are shown below.
Also beware of suspected novae near the edges of the image. The pointing of the telescope is not exactly the same for all epochs. A star may appear or disappear simply because it was cut off in one image and not another.
The images appear to shift slightly from frame to frame, and to change slightly in brightness. This is because the transparency and stability of the atmosphere change from night to night. If the air is turbulent, with pockets of cooler or warmer air, the star images become fuzzier. On a good night, the atmosphere is very transparent and steady, and the images are sharp.
Examples of good and bad nights are shown below.
|Good night||Bad night|
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