Optolong UHC Filter 1.25" Mounted

Home / Optolong UHC Filter 1.25" Mounted

Article number:	10101
Availability:	In stock
Delivery time:	In Stock!

This UHC, or Ultra High Contrast, filter from Optolong provides a bit more contrast than the CLS filter, but works in much the same way. By reducing the contrast-killing effects of light pollution caused by both artificial and natural sources, the background sky becomes darker, increasing the visibility of your favorite deep-sky objects. Skyglow, which is caused by neutral oxygen in the atmosphere, as well as light from high and low pressure sodium vapor lights and mercury vapor lamps are suppressed significantly, which means you can view or image from areas of heavy light pollution.

Optolong’s UHC filter lets desirable wavelengths pass at a peak transmission of 95%, including emission lines at OIII, H-Beta, NII, H-Alpha, and SII. This filter also has a substantial red passband, so objects like the Orion Nebula look terrific!

The Optolong 1.25” UHC Filter is made with Schott glass that has been multi-coated with an ion-assisted deposition technology to ensure scratch resistance and stability on the central wavelength, or CWL. Each filter cell is made of lightweight, strong metal and is CNC machined, sand-blasted, black anodized, and then laser engraved. The result is a super thin filter cell that will produce a clear aperture of 26mm.

Quality Filter Materials:

Schott B260 substrate material from Germany, 2.0mm thick
CNC machined and black anodized aero-metal filter cell that is ultra-thin to provide largest clear aperture; Laser-engraved to prevent fading
Multiple layers of anti-reflection non-cementing coatings applied via electron-beam gun evaporation with Ion-assisted deposition

Optolong Filter Manufacturing Processes and Parameters

Filter substrate is fine-optically polished to 1/4 wave and <30 parallelism over both surfaces
Surface quality, according to MIL-O-13830, is 60/40
95% transmission of main nebula emission lines (i.e. H-alpha 656nm, OIII 496nm and 500nm, SII 672nm and H-beta 486nm
0.1% transmission of off-band, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm)
Optolong’s planetary rotation system is a homogenous and precise coating procedure that ensures both high transmission of pass-band and optical density of off-band
Thin metal cells have a clear aperture of 26mm for 1.25” filters
Each filter comes with a plastic case with high pressure EVA case lining

The UHC (Ultra High Contrast) broadband filter is designed to improve the visibility of various deepsky objects. By selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lightings including mercury vapor lamps, both high & low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). Together with the highly transparent in main nebula emission lines at OIII(496nm and 500nm), H-beta (486nm), NII(654nm and 658nm), H-alpha(656nm) as well as SII(672nm), the filter is suitable for enhancing the contrast and details for both visual and photograghic purpose at sub-rural area with heavy light pollution.

Main Use and Performance

Suitable for color CCD cameras and unmodified DSLRs.

UHC with narrower passband provides higher contrast than CLS. Thus it is more suitable for urban environment where you suffer from severe light pollution.

UHC has a substantial red passband and offer superb views for objects like the Orion Nebula (M42).

Light pollution filter do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.

WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning.

2. UHC Spectrum for Reference