Optolong L-Pro Filter 2''

Optolong Filter This filter is designed to improve the contrast of deep-sky objects and attenuate background sky brightness, thanks to sophisticated transmission that lets through light from the lines where deep-sky objects glow (H-alpha, O-III, N-II, H-Beta, S-II...), while blocking harmful light emissions (e.g., the Hg line or sodium vapor lighting wavelengths). It also reduces background brightness caused by atmospheric oxygen (“sky glow”). Use of this filter is recommended in areas with light pollution and is suitable for both visual and photographic use.

Compared to other light pollution reduction filters, such as UHC or CLS filters, this is a multi-band pass filter that has only a minimal impact on color rendering. Therefore, it is suitable for photographing objects that emit continuous light: not only emission nebulae, but also galaxies, star clusters, reflection nebulae, etc. You can achieve exposures up to 3 times longer compared to shots taken without a filter.

Coating features: The coatings are not cemented onto the optical substrate, but applied via electron-beam evaporation followed by ion-beam assisted deposition (IBAD process). This special process allows for extreme durability and scratch resistance, ensures the stability of the central wavelength (CWL), and prevents thermal drift. Furthermore, it allows for high transmission in the passband and high optical density in the blocked frequency range. Caution: this filter must never be used alone for observing the Sun!

Main features

Optolong quality for a reliable and satisfying observation experience.

• Type: Filter
• Material: Schott glass
• Optical coating: multiple
• Connection (telescope side): 2"
• Frame: 2"
• Transmission: 95

Main technical specifications