Comet Giacobini-Zinner, November 1st 1998

Downloadable versions (see NOAO Conditions of Use):
200 x 200 9 kb color JPEG(on this page)
400 x 400 36 kb color JPEG
1600 x 1600 456 kb color JPEG
1600 x 1600 2.5 Mb 8-bit color TIFF
1600 x 1600 7.5 Mb 24-bit color TIFF

Since the comet was moving across the sky fairly quickly, and since color images are made by combining successive exposures through three different filters, a conventional combination would have either a streaked comet or a set of colored dots for each star. To avoid this, the complete sequence of images, lasting over ninety minutes, was specially processed. All frames for one color were combined with filtering that removed the moving comet: this stars-only image was subtracted from each comet frame, and the comet frames were registered and summed with further filtering to remove any residuals. The two images, with stars only and with comet only, were then added together to produce a single-color image in which neither the comet nor the stars was trailed. These three frames were then united in the final color picture, shown here.

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