A. About Optolong's UHC FIlter
The Optolong UHC (Ultra High Contrast) broadband filter is designed to improve the visibility of various deep sky objects. It does this by:
- Selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lighting (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)).
- Being highly transparent to the main nebula emission lines at OIII (496nm and 500nm), H-beta (486nm), NII (654nm and 658nm), H-alpha(656nm) as well as SII (672nm).
B. Main Uses and Performance
- Suitable for enhancing the contrast and details for both visual and photograghic purpose at urban and suburban areas with heavy light pollution.
- Suitable for color CCD cameras and unmodified DSLRs.
- UHC has a narrower passband and thus provides higher contrast than a CLS (CIty Light Pollution / Light Pollution Reduction) filter. Thus it is more suitable for urban environments where you suffer from severe light pollution.
- UHC has a substantial red passband and offer superb views of objects like the Orion Nebula (M42).
C. Spectral Curve Transmission Characteristics
- 95% transmission of main nebula emission lines:
- H-beta 486.1nm, OIII 495.9nm and 500.7nm, H-alpha 656.3nm, and SII 672nm.
- 0.1% transmission of major transmission lines of artificial light pollution:
- Hg (Mercury) at 435.8nm, 546.1nm, 577nm, and 578.1nm.
- Na (Sodium) at 598nm, 589.6nm, 615.4nm, and 616.1nm.
D. Technical Specifications
- Both surfaces are fine optically polished, accurate to 1/4 wavelength or better, and parallel to within 30 seconds or arc.
- 2mm thick Schott B270 optical glass substrate material.
- Very high surface quality of 60/40 or better (US Military Spec MIL-O-13830).
E. Optical Coating Specifications
- Multi layer anti-reflection coated.
- Non-cementing optical substrate coating.
- Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) so that there is no deviation due to temperature changes during use.
- Precise and homogeneous coatings ensure high values of desired passband and blocking of unwanted offband.
- Every single filter is tested and passed by Optolong before shipping to dealers.
- 2" astronomy filter with standard M48.5x0.75 male filter thread (no female thread, so it cannot be stacked with other filters).
- Ultra-thin filter cell to minimize vignetting; clear optical aperture of 45mm.
- Precision CNC-machined metal filter cell with sand blasted black anodized finish, anti-reflection treatment, and laser engraving.
- High quality protective plastic storage case.
WARNING: Optolong filters are not designed for direct solar observation. NEVER use these filters for observing the Sun, or permanent eye and equipment damage will result.
Jul 4, 2019
Very PleasedPros: Cons: Comments:
I purchased this Optolong broadband type of UHC for my ST-80 clone for visual use as I was concerned that a narrowband UHC- which I use on my larger telescopes-would dim the image too much due to the small aperture. I was quite pleased with the results. I used this combination in red zone skies, looking for the Lagoon Nebula and looking to test it further with the Trifid Nebula, with good results.The Lagoon was initially found without the filter, visible as a small cluster of stars without nebulousness,rather plain looking. With the filter the nebula was readily visible. The stars were dimmed but not a lot, much less so than with a narrowband UHC, It was a lovely sight. I then found the Trifid Nebula with the filter still on, quite easily recognizable. While the Trifid nebula was dim the dark lanes could be made out.
Stars viewed with the filter remained sharp throughout the field. Build quality appears to be very good. Overall I am very pleased with this purchase.
This review was provided courtesy of AgenaAstro.comMar 16, 2018
optolong cls clip filterPros: Cons: Comments:
It's size is not perfectly matched to Nikon D600 full-frame.
(slightly larger than camera's region).
So, it was a bit difficult to place it correctly inside the camera using tweezers. The frame metal is very thin and week~!
For the case of D600 full-frame, there is about 10-15% Vignetting effects on the edge of image frame, but the CLS-filter is working anyhow.
This review was provided courtesy of AgenaAstro.comFeb 13, 2018
Excellent Clip-in Filter for Nikon D7100Pros: Cons: Comments:
This filter’s performance exceeds my expectations. I shoot from a suburban backyard with light pollution from Baltimore to the Northwest, Annapolis to the North, and Washington DC to the West. I am getting images with this filter I could not have dreamed off before I bought it. Note that you cannot use this filter with some Nikon lenses with protruding pins on their bayonets. Works great with a T-adapter.
This review was provided courtesy of AgenaAstro.comAug 4, 2017
Excellent Broadband filter!Pros: Cons: Comments:
"UHC" is a descriptor whose meaning has become muddled by manufacturers. Originally UHC applied to a narrowband (~28nm bandwidth) filter. Today broadband filters such as the Optolong UHC (~48nm bandwidth) are also given the UHC label. The Optolong UHC is an optically excellent filter but it is important that the buyer understand that it is a broadband filter and what that means for use. At exit pupils larger than about 2mm the Optolong UHC does not enhance contrast of nebula as much as a narrowband UHC filter, but it does enhance contrast noticeably. However, if you increase the magnification so that the exit pupil is less than ~1.5mm the Optolong UHC enhances contrast of nebula more than a narrowband filter. So this Optolong UHC filter is a great filter because of its flexibility. It is useful at low magnifications, but it is very useful at high magnifications. The optical quality is excellent. The image is sharp and the threads are of excellent quality. I also really like the case it comes with. It is very easy to grab the filter without touching the glass.
This review was provided courtesy of AgenaAstro.comJan 15, 2017
ExcellentPros: Cons: Comments:
Optolong filters are totally quality...I bought this filter for my OSC cameras the combination of the UHC nebula and the L-pro are the perfect duo if you live in a heavy polluted are like me.,
This review was provided courtesy of AgenaAstro.comSort by