Optolong 2" L-Pro Light Pollution Filter

The Optolong L-Pro (L-Professional) 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 light 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 transparency of the main nebula emission lines at OIII (496nm and 500nm), H-beta (486nm), NII (654nm and 658nm), H-alpha(656nm) and SII (672nm), the filter is suitable for enhancing the contrast and details for both visual and photographic use in areas with heavy light pollution.

Optolong L-Pro is multi-bandpass filter which offers better color balance by maximizing the transmission band. The balanced transmission allows astrophotos to be taken with minimal colour cast on broadband emission objects such as galaxies, reflection nebulae and globular star clusters.

Main Use and Performance

Suitable for visual observation and astrophotography.

L-Pro filter has a very low transmission reduction rate against continuous spectrum space objects, and thus is quite effective in suppressing light pollution sources when shooting galaxies, reflection nebulae and globular star clusters. The same holds true for visual star observations.

L-Pro filter alone can suppress infrared wavelength, and thus can be used at ease for “L” image shootings with CCDs.

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.

In general Astrograph recommends the L-Pro as an ideal partner for use with One Shot Colour Cameras (OSC) CMOS Cameras for supression of light pollution and enhancement of emission objects.

WARNING: Optolong filters are not designed for sun observation. DO NOT LOOK AT THE SUN WITH AN OPTOLONG FILTER.

Technical Data

• Optical glass

• Spectrum: 380-750nm

• Surface Quality: 60/40 (Refer to MIL-O-13830)

• Fine-optically polished to ensure accurate 1/4 wavefront and < 30 seconds parallelism over the both surfaces

• High transmission at major nebula emission lines (i.e. H-alpha 656nm, OIII 496nm&500nm, SII 672nm and H-beta 486nm).

• Precision off-band blocking, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm).

• Thickness 2mm (add 0.7mm to the back focus specification of a corrector)

  Multi-layer anti-reflection coating

  Non-cementing optical substrate coating

  Optolong L-Pro filter adopts precision coating based on Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL(central wavelength) no deviation affected by temperature change.

  Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band.