Optolong Variable Polarizing Filter - 2”
With the Optolong Variable Polarizing Filter, you can easily modify the brightness level of the Moon, Venus, and other bright objects. A typical Moon Filter is like a pair of sunglasses; they work okay, but sometimes the scene is too bright or too dark, and there isn't a lot you can do about it. That's why many astronomers prefer the flexibility of a variable polarizing filter. It will let you to set the percentage of attenuation by turning the top section of the two-piece filter. Simply attach the 2” threaded filter to a like-sized eyepiece or astro accessory barrel, and then slowly rotate the top half of the filter—it turns 360°—to achieve the results you desire. Now you can apply more filtering to a full moon and less to a beautiful crescent—it’s your call!
The Optolong 2” Variable Polarizing Filter also works great to cut brightness when you are using your telescope for terrestrial observations or photography. If you have ever done photography through an SLR or DSLR camera, you may have already been introduced to the qualities of a polarizing filter, since it is a very popular accessory for polarizing the light and making the sky appear bluer. You will especially appreciate a polarizing filter when viewing over water or photographing a scene that includes a river or body of water. Simply turn the filter until you achieve the most glare-free results—you will really see the difference!
The Optolong 2” Variable Polarizing 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. The 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 45mm.
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
- High-value transmission of pass-band and optical density of off-band is assured through Optolong’s planetary rotation system, a homogeneous and precise coating procedure
- Thin metal cells have a clear aperture of 45mm for 2” filters
- Each filter comes with a plastic case with high-pressure EVA case lining
Optolong is the Astronomy Filters division of Yulong Optics, an optical filter design, and processing company out of Kunming, China that has provided filters for over 700 optical companies since 1999. All Optolong filters pass European Union RoHS requirements and have been certified by TUV Rheinland and Bureau Veritas.
Optolong 2" Variable Polarizer Filter
- Filter Case
Dimensions & Specifications
Filter Size: 50.8 mm (2")
Filter Type: Moon/ND/Polarizing
Filter Shape: Round
Mounted or Unmounted: Mounted
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