melissa

	Right Ascension: Declination: Apparent Magnitude: Apparent Diameter: Constellation: Exposure Time: Resolution Mode: Signal/Noise:	10h 24m 46.4s 18° 37' 55" 9.0 20.8 arc min. Hydra 2 seconds RGB Filter Medium 20

Planetary nebulae are shells of gas thrown out by some stars near the end of their lives. In fact, our Sun will probably produce a planetary nebula in about 5 billion years. They have nothing at all to do with planets; the terminology was invented because they often look a little like planets in small telescopes. A typical planetary nebula is less than one light-year across and the gas shell often appears to be red in color due to H-alpha lines. The Ghost of Jupiter planetary nebula was named because of its supposed resemblance to the planet Jupiter. This planetary nebula is one of the brightest in the sky. It's gas shell has an elliptical ring structure and is blue in color. If you look closely in the image above, a white dwarf can be seen in the center of the gas shell.

This image was taken on March 17, 1999 under fairly good sky conditions. The sky was clear, but the Moon was almost full and therefore very bright. The image was taken using RGB filters, with a two second exposure time for each filter. The exposure time is so low because this image was supposed to be a test image, with a better quality image to be taken later in the semester. However, due to cloudy skies and many students waiting to observe, there was never a chance for a better image to be taken. The image could be improved by changing several things. First, a higher signal-to-noise ratio would be better. The S/N ratio for this image is 20, while a S/N ratio of 100 or greater is preferred. Increasing the S/N ratio can be accomplished by increasing the exposure time. Also, changing the resolution mode from medium to high would create a better image. Lastly, taking the image on a night when there isn't so much light from the Moon would help image quality. Sometimes taking a flatfield for the image will help clean it up. In this case, a flatfield wouldn't have been too helpful because the exposure time was only two seconds which isn't enough time for variations within the camera to have a significant effect.