Check the listing for details. Optolong L-Ultimate 1.25" Dual Bandpass Light Pollution Reduction Imaging Filter. Condition: New. Listed at 289.00 USD. Optolong 3nm L-Ultimate Dual Narrowband Filter for Astronomical Color Camera Light Pollution DecreaseAdvantage:- The advantage of L-Ultimate is that it only passes through the emission lines OIII (500.7nm) and Ha (656.3nm) of the nebula, and in this case, all other light contaminated rays are cut off, so that only the signals of the emission and reflection nebula can be obtained during imaging. Therefore, it can make the sky background of the image darker, and maximize the contrast and signal-to-noise ratio between nebulae. In areas severely affected by light pollution, this product can also selectively filter out light pollution and noise signals through nebular emission lines, ultimately avoiding the impact of light pollution on astronomical photography.- The difference between this product and the same series of dual narrowband L-eNhance and L-eXtreme lies in that L-Ultimate is a dual 3nm bandpass filter that only passes through Ha and OIII emission lines, which can obtain a darker sky background in photography, and has stronger suppression on star points, contrast between nebulae, and contrast enhancement. The filter has also been optimized in terms of halo performance, so there will be no obvious halo when shooting bright star targets.Specification:- Filter material: optical glass- Filter thickness: 1.85mm- Bandwidth value: OIII 3nm; Ha 3nm- Cutoff range: 300 - 1000nm- Cutoff depth: > OD4- Degree of finish: 60/40- Surface shape: λ/4- Depth of parallelism: 30 secondsPackage Included:- 1 x Filter