Baader Clear Filter 2" mounted, full transmission also in IR

Baader CCD Clear Glass Filter

Clear glass filters let through the complete light spectrum and also allow the use of infrared light. The most important application areas of the filters are:

♦ Deep-sky photography with reflector telescopes without corrector
Normally an IR cut filter is needed for astrophotography because lenses or correctors are not corrected for the infrared light. The sharpness would be greatly reduced. The CCD chips are sensitive well into the infrared. With purely reflecting telescopes without a corrector, the complete IR light can be used, you gain up to 15% more light and have significantly more information on the chip at comparable exposure times. The clear glass filter protects the camera sensor from dust.

♦ Luminance images taken with monochrome astro cameras with reflector telescopes without corrector
It makes sense to use a filter with the same thickness for the luminance recording as for the color channels. This saves refocusing. Baader filters with the same diameter always have the same thickness.

♦ Focusing with narrow band line filters
Setting the correct sharpness with dark filters is a problem. The C-filter replaces the 2" narrow band filter of the same thickness for precise focusing. Then simply replace the clear glass filter with the Baader narrow band filter and you´re ready to go.

Mechanical properties:

♦ the only filters with homofocally plane-polished substrates. Each individual filter is polished to 1/4 wavelength for fine optics
♦ Baader filters are hardcoated separately. The individual filters are not drilled out of large plates as usual.
♦ drilled out filters show micro cracks at the edge of the quenched and tempered layer, which tend to absorb moisture due to capillary action
♦ all Baader filters have individually coated heat-treated edges, so moisture penetration is impossible
♦ Baader filters were boiled in water for one hour during long-term ageing tests (for example at B+W Filter/Schneider Kreuznach) and, in contrast to drilled filters, remained completely undamaged.
♦ scratch-resistant hard coatings of Baader filters can be cleaned as often as required - preferably with Baader OpticalWonder cleaning liquid

Optical properties

♦ no reflections in comparison to competing filters
♦ maximum contrast due to extremely steep edges on all transmission curves

♦ Clear glass filter in protective container