| The relatively narrow passband of this Bandmate 1.25" UHC (Ultra High Contrast) filter provides 2x to 4x higher contrast than the wider passband of the typical broadband filter. The filter has excellent transmission at the visually important emission lines of hydrogen-beta at 4861Å and doubly ionized oxygen at 4959Å and 5007Å, with high blocking of the unwanted longer wavelengths where light pollution from city lights lurks. The relatively narrow passband and high transmission combine to make faint emission nebulas such as the Helix, Rosette, Veil, and North American stand out briskly against a dark background from moderately light polluted observing sites. Brighter nebulas (such as the Omega, Dumbbell, Lagoon, etc.) stand out well under city lights. It can also be very useful in hunting down and enhancing very faint nebulas from a dark sky observing site. The filter works best with telescopes 4" to 5" and larger in aperture. Users of smaller 4"-8" telescopes will especially appreciate the high efficiency, and larger scope users will love the rich star fields and detailed subtle nebular shadings that are left intact. The filter is designed primarily for observing emission nebulas. It is not designed for astrophotography or for observing the primarily violet reflected starlight of reflection nebulas. The filter substrate is ground and polished optical quality BK7 glass. This yields sharp star images, even when the filter is placed in front of the star diagonal. Such a location results in a long light path between the filter and eyepiece. This can reduce the image sharpness in lesser filters whose glass substrates are not polished to the same plane and parallel accuracy as TeleVue filters. Multilayer ion beam coating technology and the high quality optical glass produces low scatter in its stable hard coating. This reduces passband changes due to temperature and humidity. Each filter is checked optically and cosmetically to assure performance and each is individually serialized. Special filtering in the TeleVue passband design reduces the red tinge in stars so often seen in lesser filters. It also allows for sharp and bright views of star clusters embedded in nebulas, such as M8 (the Lagoon). This TeleVue filter does not dim these stars to the extent traditional filters do. The TeleVue nebula/star brightness balance is more realistic. In addition to better views of embedded star clusters, the TeleVue Bandmate UHC filter shows more stars in the background field than traditional filters. Here are a few comments about this effect from on-line customer comments. “The nebulae were being equally enhanced with the Bandmates but not at the expense of filtering out the background star field to the degree seen in competitive filters. In addition, the star colors appeared, in the Bandmates, truer. How is this done? Not a clue, but the difference is more than just subtle. The resulting views through the Bandmates were to me more realistic and aesthetically more pleasing. I noticed this most on M42 and the Dumbbell where the field stars add greatly to the enjoyment of the over all view. To date the two Bandmate Nebula filters are the best that I have ever used."
“I was very surprised at how many stars were visible with the filter in place. Also, the stars are esthetically pleasing and were not artificially tinged red which I’ve heard happens with other filters. The filter was placed before the diagonal making it a breeze when changing eyepieces." 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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