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High-contrast Filters

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Posted by Daniel Johnson on November 10, 2002 05:16:37 UTC

Since Lumicon has now gone out of business, you would have to find their filters second-hand. I have both their broadband and high-contrast varieties, as well as their Oxygen-III variety. I was disappointed with the broadband filter but quite pleased with both the high-contrast and Oxygen-III filters. If you want to be able to see, say, the Orion nebula from within a small city's light, get a high-contrast filter (Orion's should do the job). The Oxygen-III gives a slight gain over the high-contrast for a few objects, such as the Veil nebula, but I find it most useful when I'm at a dark-sky site. None of these filters makes the Veil visible from my home town (city of about 200,000 people) but the high-contrast makes a huge difference for several nebulous objects in town, and both the high-contrast and O-III filters are good for dark sky sites.
If you can get only one filter, go for high-contrast. Realize that these filters are most useful for only emission nebulae and perhaps a few reflection nebulae, but they don't help much with galaxies or globular clusters. One possible exception: if you're lucky enough to have local city lights that match the blocking properties of some particular filter, that filter might help for many kinds of objects. But city lights vary a lot in their type, and most cities have a mix of many different lights--it's hard to know what wavelengths of light pollution you have locally, unless you own a spectroscope!
In short, get the high-contrast if you want an all-around filter for visual use in and out of town on emission nebulae (including the Ring, Orion, and so on).

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