The new Optolong L-Ultimate is a dual-band astrophotography filter designed to drastically reduce the effect of light pollution. Its two ultra-narrow 3nm passing bands isolate the nebulae emissions in H-Alpha (red) and OIII (green-blue), maximizing signal and making the sky background dark. The L-Ultimate filter has been optimized for excellent halo performance. The L-Ultimate is designed for use with optics not faster than f/4. For example, with a RASA at f/2 there will be too much band shifting for the desired signal to pass through. It blocks the artificial light from mercury vapour lamps, both high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). Maximum transmission of the main nebula emission lines at OIII (500nm) and H-alpha (656nm). Two transmission bands with a bandpass of 3nm. Designed mainly for astrophotography. Ideal for urban areas with extreme light pollution. It incorporates an IR/UV-Cut filter that is necessary in astrophotography, especially for astronomy cameras that are sensitive to the infrared radiation. Ultra-thin filter cell to maximise the compatibility with most filter wheels. Multi-layers anti-reflection coating. Cell in Aerometal Material, CNC machined, sand blasted, black anodized and laser engraved. Plastic PP Case, high pressure EVA Case Lining. Light pollution filters do not eliminate the effects of light pollution or increase the object’s brightness. It does increase the contrast between nebulae and night sky. The interferential coating is deposited on the substrate using electron-beam gun evaporation with Ion-assisted deposition coating technology. This increases the filter durability and resistance to scratching, as well as stability on CWL (central wavelength) and no deviation affected by temperature changes. The planetary rotation system offers precision and homogeneity of coatings ensuring high transmission of pass-band and high optical density off-band. WARNING: Optolong filters are not designed for sun observations. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTERS. You could become BLIND if you fail to observe the warning. The L-Ultimate has excellent control of halos around bright stars. Credit: Tommaso Massimo Stella. Specifications Passing band Dual-band H-alpha and O-III 3nm Glass thickness 1.85 mm Optical flatness 1/4 λ (wavefront) Bandpass transmission ~90% Coating Fully multi-coated Surface quality 60/40 Parallelism 30" Glass type Monolithic optical substrate (non glued) SKU OP-9998 (1.25"), OP-9999 (2") Gallery NGC7000 in LHaRVB by Nicola Martino | Optolong L-Ultimate, Takahashi FSQ-85EDX, ZWO ASI2400MC Pro OU-4 by Tommaso Massimo Stella | Optolong L-Ultimate & L-eXtreme, TS PhotoLine 102, Takahashi FS60CB, ZWO ASI294MC Pro Sh2-132 by Andrea Maggi | Optolong L-Ultimate W63 by José Jiménez | Optolong L-Ultimate, modified Canon EOS 5D Mark IV
