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Posted by Daniel Johnson on April 18, 2003 03:16:04 UTC

I can answer a few of your questions:

Get the narrow-band filter if you plan on visual observing from the city. I didn't find the broad-band very useful. Keep in mind that it will only help if you're looking at objects that emit at specific wavelengths (emission nebulae especially), and will be of little use on objects like galaxies, which (like the city lights) emit at nearly all frequencies.

Go for the eyepiece kind, not the rear-cell kind. One possible exception: I have the two-inch IDAS filter. It comes a little closer to giving realistic colors on photography. I've used it for a little film photography from my home town, though our light pollution isn't terrible compared with some. For that one purpose (photography on film from town), cosider the rear-cell type or (better yet) a two-inch filter. The latter will fit a two-inch star diagonal or two-inch T-adapter. But for planets you don't need a light-pollution filter, and they're the best objects for photography from town. Keep in mind that planetary photography is now done almost exclusively by digital means--digital cameras, camcorders, CCD cameras, or web cams. One averages many exposures electronically to get the final image, and film just can't compete anymore for planets. Film is still great for deep sky targets.

If you're doing film photography, get a TWO-INCH T adapter, and in addition you need an adapter to connect the T threads to your specific brand of camera. The two-inch T adapter will give you a slightly wider area without vignetting, though that's less an issue with 8-inch scopes than with larger ones. The 8-inch scopes have about a 1.5-inch light path through the central perforation in the mirror, so you lose a little light at the edge of your film frame with 1.25-inch T adapters.
You won't use eyepiece projection much--that's a technique that was used a lot in the days of film planetary photography. You'll want a photo reducer (f/6.3 for film) to reduce focal length, not an eyepiece projector--that is, you'll want to change magnification DOWN for faster exposures of deep-sky objects.
(Also, a film scanner is a great accessory, but not cheap. My CanoScan FS2720U serves me well. At $300, it was the cheapest film scanner that seemed worth getting 5 or 6 months ago. Prices may be falling--I haven't checked--but many film scanners were priced twice as much.)

I don't know about the specific Barlow you mention. General rule: DO NOT try to save money on an inexpensive Barlow. Go big or don't go at all. A cheap Barlow is worthless trash that you will curse forever. Celestron's Ultima has served me well. My friends rave about their TeleVue Powermates. TeleVue doesn't sell anything of poor quality.

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