H-? filter in a 2-inch frame for visual observations and astrophotography of Deep Sky objects in the H-Beta band (approximately 486.1 nm). It improves the quality of images of weak objects such as Horsehead, allowing them to be seen even in conditions of significant light pollution.
- transmission for a length of 486 nm (corresponding to the H-beta line) equal to 91%
- a filter in a metal frame with filter threads on both sides of the luminaire
- high precision of optical surfaces (parallelism)
- covered with good quality anti-reflective layers
- transmits light with a range from 470 to 493 nm
- intended for use in telescopes with a minimum diameter of 20 cm
(measurements on the Varian Cary 100 spectrophotometer, July 2015)
Connection of ALL astronomical filters with the exception of solar film filters (which are filters for the lens) is accomplished by screwing the filter into the frame of the eyepiece from the opposite side than applying the eye (ie from the side that we put in the eyepiece extractor) . The filters can be additionally connected with each other, because they have threads on both sides of the luminaire.