Optolong IR Pass (685nm) Filter - 2"

The Optolong IR Pass 685nm Filter blocks wavelengths below 670nm to enhance contrast and surface detail and reduce the effects of seeing when used in IR-LRGB imaging of the moon and planets. Atmospheric seeing and distortion diminish as you move further away from visible light into the infrared, and since CCD and CMOS sensors are sensitive to IR light, imaging in the infrared will improve your results.

The IR Pass 685nm filter offers a 95% transmission at bandpass.

The Optolong 2” IR Pass 685nm 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 at passband
• High value transmission of pass-band and optical density of off-band is assured through Optolong’s planetary rotation system, a homogenous 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

About Optolong

While Optolong is a relative newcomer to the astronomy industry, they are no strangers to optics and filters. Optolong is a division of Yulong Optics Company, a high tech company specializing in optical filter design and production. Their products include bandpass filters, flourescence filters, edge filters, longpass and shortpass filters, beam splitters, anti-reflection coatings, optical mirrors and, of course, astronomical filters.

Established in 1999 and based in Kunming City, China, Optolong/Yulong provides nearly 2000 types of optical filter coatings annually to customers worldwide in a wide variety of industries and applications.