Optolong Filters L-Para 2" (85360)

The Optolong L-Para 2" filter is a dual narrowband light pollution filter designed to significantly enhance astrophotography, especially in environments affected by urban or suburban light pollution. It is optimized for both standard and fast optical systems, including setups with focal ratios as low as F2, making it compatible with a wide range of telescopes and imaging trains. The filter isolates the key emission lines of nebulae-OIII at 500.7 nm and H-alpha at 656.3 nm-each with a narrow 10 nm bandwidth. This design allows for high transmission of nebula light (over 85%) while effectively blocking unwanted light from sources such as mercury, sodium, and LED lamps. The result is images with a dark background, vivid colors, high contrast, and minimal halos around bright stars. The L-Para filter is ideal for capturing emission nebulae, planetary nebulae, supernova remnants, and galaxies, even under Bortle 1 to Bortle 7 skies.

Key Features and Specifications

Coating of optical system: Multiple anti-reflection layers for durability and high performance

Frame: 2-inch metal cell (M48 x 0.75 thread), compatible with most filter wheels and drawers

Mount material: Aluminium for strength and lightweight design

Transmission: Greater than 85% at OIII (500.7 nm) and H-alpha (656.3 nm) emission lines

Surface accuracy: 4 (high optical quality)

Connection (to eyepiece): 2-inch diameter for broad compatibility

Type: Dual narrowband UHC (Ultra High Contrast) filter

Material: Optical glass, 1.85 mm thick

Blocking range: 300-1000 nm, with optical density OD > 4 for strong rejection of unwanted light

Photographic use: Yes, highly suitable for deep-sky astrophotography

Anti light-pollution: Yes, effective against mercury, sodium, and LED light pollution

Visually useful: No, designed for imaging rather than visual observation

Nebulae & galaxies: Yes

Planetary nebulae: Yes

Hydrogen nebulae: Yes

Supernova remains: Yes

Galaxies and star clusters: Yes

H-alpha: Yes

This filter is an excellent choice for astrophotographers seeking to capture detailed and vibrant images of emission nebulae and other deep-sky objects, while minimizing the impact of light pollution and halos from bright stars.