The 1.25 "dual-band Optolong L-Extreme filter is an excellent tool especially for photographing bright emission nebulae with digital SLRs and monochrome cameras in conditions of high light pollution.
This filter transmits over 90% of the light in the spectral lines emitted by ionized hydrogen (Hα) and oxygen (OIII) atoms. The half-width of the transmission bands is only 7 nm, therefore the OIII line is very well separated from Hβ. The narrow half-width (FWHM) in combination with the efficient cutting of spectral lines characteristic of sodium and mercury lamps, allow for the recording of sharp and contrasting images even near large cities. In addition, the narrow bandwidth provides a significant gain of contrast during bright moonlit nights or when photographing emission nebulae glowing in transmitted bands, eg near bright stars.
In order to further improve the optical parameters, this filter is covered with a full multi-layer anti-reflection coating applied using ion implantation techniques. Thanks to this, the coatings are not only perfect in terms of optics, but also very durable and scratch-resistant.
• high transmission dual-band filter for Hα and OIII lines
• efficiency of cutting out light pollution at the level> 99%
• scratch-resistant multi-layer anti-reflective coating
• filter type: dual-band filter
• filter diameter: 1.25 "
• Half bandwidth: 7 nm
• pass bands: Hα, OIII
• maximum transmission:> 90%
• blocking range: 300 - 1000 nm
• efficiency in blocking light pollution:> 99%
• Filter material: Schott B 270 glass
• type of coating: full multilayer coating (FMC)
• filter thickness: 1.85 mm
• surface quality index: 60/40
• parallelism: 30 "
• RMS execution accuracy: λ / 4
• frame material: aluminum
• Optolong L-Extreme 1.25 "filter