The L filter is a standard Baader UV/IR blocking filter and can be used for focusing, as well as for taking a luminance image. The C filter is clear glass, and is only used for focusing.
Mechanical properties:
- the only parfocal filters with plane-optical polished substrates. Each filter is precision optically polished to 1/4 wavelength
- Baader LRGBC filters are separately hard-coated. The individual filters are not cut out of large plates
- cut out filters have micro-cracks at the edge of the coating layer which tend action to absorb moisture by capillary action
- all Baader filters are individually coated, hence the coating edges are sealed - meaning the penetration of moisture is impossible
- during long term aging tests, Baader filters (including B + W filters/Schneider Kreuznach filters) were boiled in water for an hour and remained completely intact, in marked contrast to cut out filters
- the hard scratch-resistant coating on Baader filters can be cleaned as often as required
- Optical properties: no reflections - as is the case with competing RGB filters
- the balanced RGB design allows imaging at the same exposure times - very important for automated serial exposures
- maximum colour contrast for each of the three RGB channels due to extremely steep slopes for all transmission curves
- OIII emission lines in the B and G channel are double weighted, with maximum transmission - for the highest deep sky quantum yields
- R filter delivers maximum transmission and contrast in H-alpha and SII, but blocks IR from 680 to 1200nm
- blocking between g and R filter reduces light pollution of mercury and sodium vapour lamps at 580 nm, darkens the sky background, and improves colour balance and colour separation
- Blocking between the G and R filters range reduces the light pollution arising from mercury and sodium vapour lamps at 580nm, darkens the sky background, improves colour balance and improves colour separation.
