Anyone remember the Problicom program run by Ben Mayer in LA? There are at least a couple of us here on UA that participated in that program back in the 70s, 80s and early 90s. As Chuck mentions we'd take pictures of the same areas of the sky once a month and then "blink" them using two slide projectors and an occulting disk. Taking the pictures was easy but scanning them was a real pain as one could never get the images to line up exactly so the images were always jumping back and forth or up and down. And the many variable stars and "Kodak novae" (tiny defects in the images that looked like stars) did not help either. It's soooo much easier today. Just shoot a couple of digital images, stick them in a program like CCDSoft and the software aligns them precisely, blinks them and even highlights any possible novae. Memory lane... pw On 21 Feb 2007, at 09:57, Chuck Hards wrote:
Novae used to be discovered by "blinking". Two photographs of the same region would be taken, days, weeks, or months apart, and the researcher would compare the two by looking at each in rapid succession on a device called a "blink comparator". Any star seen on one but not the earlier photograph would appear to blink on-and-off.
It would be an easy, straightforward project to do the same thing on the computer, with digital images. Amateurs can easily discover novae, even today.
One popular low-tech approach from another decade was the projection comparator. Two identical slide projectors with a motorized, rotating shutter in front of the lenses, so that only one slide at a time was projected. This was the "astronomy club" method. Also easier on the eyes than staring into a bino or mono viewer for extended periods of time.