Product Description
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.
Click on the Light Pollution Filter Formula under the Formula tab above and enter your telescope focal ratio in the formula box to see what focal length eyepieces will work best with this filter.
Tech Details
| Max City Exit Pupil | 2mm |
|---|---|
| Max Dark Site Exit Pupil | 4mm |
| Min City Exit Pupil | .5mm |
| Min Dark Site Exit Pupil | 1mm |
| Weight | 2 ozmm |
Reviews
Review by: Rex
Living in a red light pollution area about 15 miles from downtown Washington DC- using some form of filter for light pollution is a necessity while doing visual and imaging work. With this filter I am able to get ~30-40% longer exposures, however as noted in the description, there is a loss of fine detail- especially with reflection nebulosity (M45 comes to mind). Color balance isn't shifted too badly and is easy to correct in post processing. Overall a good all-round filter if you have to deal with light pollution regularly. With the rise of LED lighting however, I think this filter, and my Orion Skyglow are becoming less and less effective as time goes on. (Posted on 10/31/2018)