Filter for digital cameras and webcams for photographing the calcium line of the solar spectrum
The Calcium GEN-II filter opens up the interesting border area between the photosphere visible in white light and the chromosphere of the Sun, which is reserved for narrow-band H-alpha filters. In addition to the structures known from white light, such as sunspots, the network of chromospheric flares distributed across the entire surface of the Sun, which precedes the formation of sunspots, as well as supergranulation cells and Ellerman bombs, become visible.
The calcium line is at 394 nm and therefore in the near UV range. This means that observation of the Sun is only possible with a camera! Never use the filter visually, as the eye is blind to harmful UV radiation but can be damaged by it.
The filter achieves the best results with a monochrome camera (which is more sensitive in this spectral range than a colour camera) and on pure mirror telescopes (as fast lens telescopes in particular are not optimised for this edge range of the UV spectrum). However, many refracting telescopes still produce sharp images in the calcium window; with unmodified DSLRs, extremely long exposure times may be necessary because many camera models do not allow transmission below 400 nm.
Scope of delivery: The filter comes with an AstroSolar film with ND3.8 (size 20 x 30 centimetres). This film is used to pre-filter the intense sunlight and must be used by attaching it to the telescope tube. The film and filter are only suitable for use with a camera, not for visual observation!
New: The Calcium GEN-II replaces the previous K-Line filter from Baader. Thanks to modern manufacturing techniques, a single filter now achieves better quality and a narrower half-width of only 5 nanometres instead of the previous 8 nm, meaning that stacking two filters is no longer necessary. This also makes it possible to use the filter in standard filter wheels/drawers.
The filter offers all the advantages of CMOS-optimised Baader filters:
- Increased contrast, tailored to typical CMOS quantum efficiency and s/n ratio
- Reflex-Blocker™ coatings for maximum insensitivity to retro-reflection from nearby auxiliary optics, even under the most adverse conditions
- Identical filter thickness to existing standards, with the utmost care taken to ensure homofocality
- Blackened edges all around, with filter front indicator in the form of a black outer edge on the telescope side to additionally prevent any reflection from light falling on the filter edge
- Each filter is individually precision-polished and coated, with a sealed coating edge (NOT cut from a larger plate, which would leave the coating edges exposed).
- Life-Coat™: even harder coatings to enable an age-resistant coating with an unlimited service life – even in the most adverse environments
