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| This 48mm filter for 2" eyepieces has a moderately wide 560 Ångstrom passband for use in slight to moderately light polluted areas. This filter is primarily for visual use on emission nebulas with medium to long focal length 2" eyepieces. It typically has a peak transmission approaching 96% at the visually important emission lines of hydrogen-beta at 4861Å and doubly ionized oxygen at 4959Å and typically a somewhat lower (but still good) transmission approaching 88% at the 5007Å doubly ionized oxygen line. While its 48mm thread size will fit a number of off-axis guiders and camera adapters, its transmission at the photographically important ionized nitrogen and hydrogen-alpha lines near 6570Å is only fair, making it less than ideal for photographic work. It has fair performance on reflection nebulas due to its moderate passband, but a wider passband filter would show more reflected starlight detail. It has very steep passband cutoff slopes that yield higher contrast than competitive filters of a similar passband width that have more gradual transition slopes. Enter your telescope focal ratio in the formula box to the right to see what focal length eyepieces will work best with this filter.
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Terms of Sale | PRIVACY POLICY 7/1/2004 | Fine Print
Toll-Free Telephone Astronomics: 800-422-7876; Christophers, Ltd.: 800-356-6603
Alternate Telephone: 405-364-0858 24 Hour Fax Line: 405-447-3337
Telephone Hours: Monday 8 AM - 6 PM CST
Tuesday-Friday 8 AM - 8 PM CST
Saturday Noon - 5 PM CST
Store Hours: Monday-Friday 9 AM - 5 PM CST
Saturday Noon - 5 PM CST
Astronomics / Christophers, Ltd.
680 S.W. 24th Ave.
Norman, OK, 73069
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