A set of three narrowband filters with a half width of 7 nm. Narrowband filters do not eliminate the effect of light pollution and do not increase the brightness of objects - but in many cases they greatly increase the contrast between an object and the night sky in the background.
The kit includes a hydrogen filter (H-alpha band), oxygen filter (O-III) and sulfur filter (S-II). Together, they allow the observation and - above all - a color photograph of nebulae (emission, planetary nebulae, remnants of supernova explosions) even in conditions of the highest pollution with artificial light. Three SHO filters form the so-called Hubble palette (SHO assignment with respect to RGB channels: sulfur signal - S - falls into channel R, hydrogen signal - H - falls into channel G, and oxygen - O - is assigned to channel B ).
• FWHM: 7 nm +/- 0.5 nm
• glass thickness: 1.85 mm +/- 0.03 mm
• 1/4 λ accuracy for the wave front
• transmission: about 90% for the 656 nm line (hydrogen filter), about 90% for the 672 nm line (sulfur filter), about 90% for the 500 nm line (oxygen filter)
• Transmission <0.1% for the length beyond the filters' pass-through
• cut infrared in the range of 700 - 1100 nm
• MC coatings
• filter holder (length): 5.5 mm + 3.5 mm thread
• thread: M48 * 0.75
• size: 2 "