I'd have to think on that definition, and test it at the eyepiece...I don't think that they actually lighten similarly-colored tones- filters should darken them also; just not as much. Contrast is still increased. Feel like a testing session this weekend, if I can clear it with the boss? I was at SPOC tonight, using the 32", but didn't use colored filters on Saturn since I was with a training group- though I did bring my "arsenal" (eyepiece/filter box). One of the best views of the Eskimo nebula I've ever had- and I didn't have to freeze my *ss off to see it, either... On 5/9/07, Kurt Fisher <fisherka@csolutions.net> wrote:
Chuck,
Okay, here's the short rule-of-thumb for colored filters that I was looking for:
"What you see is that a filter lightens tones of objects colored similarly to the filter and darkens tones of objects colored dissimilarly." Kodak. 1998. Using Filters (Kodak Workshop Series) (The Kodak Workshop Series) (Paperback).
So, a red filter on Mars lightens the reds and darkens the blue polar ice caps and the blue-green maria.