Optolong Neutral Density ND3 Filter - 1.25”
The 1.25" ND-3.0 is a neutral density filter designed by Optolong that has the option to be used with a solar wedge or on an eyepiece to counteract the brightness of an object overall without modifying the color balance. Neutral density filters are a favorite among Moon observers because they retain an object’s true color since all wavelengths of light are transmitted uniformly. However, they can be very useful for a wide range of observations. Use the ND3 filter to split double stars, observe Venus, or experience a more detailed view of the Moon. The Optolong Neutral Density Filter has an ND-3.0 rating, and so it has a 1,000 reduction factor and a transmission of 0.1%.
The Optolong 1.25” Neutral Density ND3 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 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
- 1000 reduction factor, 0.1% transmission
- Optolong’s planetary rotation system is a homogenous and precise coating procedure
- 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
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 1.25" ND3 Filter
- Filter Case
Dimensions & Specifications
Filter Size: 31.75 mm (1.25")
Filter Type: Moon/ND/Polarizing
Filter Shape: Round
Mounted or Unmounted: Mounted
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