The Baader C2 SWAN-Band-Filter isolates the two C2 lines at 511 and 514nm.
These two emission lines, named Swan bands after their discoverer, dominate the spectrum of a comet's gas tail in the visible range. The filter allows only the light from the two carbon bands to pass through and, among other things, blocks the ubiquitous stray light, similar to a nebula filter in deep-sky observation. Structures in the gas tail thus become clearer even under good observing conditions.
At the same time, it completely blocks the OIII line at 501nm and below, which other Swan-Band filters allow to pass. This allows for even higher contrast, and comets with gas tails can be distinguished even better from those dominated by a dust tail (and where a SWAN filter provides only a small contrast enhancement).
For ambitious comet observers, a SWAN filter is part of the basic equipment.
Baader's CMOS-optimised filters are characterised by:
- increased contrast
- narrower half-widths (FWHM)
- Reflex Blocker™ coatings for maximum insensitivity to retro reflection from nearby auxiliary optics, even under the most adverse conditions
- FWHM carefully designed for each filter category to enable 1:1:1 exposures, matched to typical CMOS quantum efficiency and signal-to-noise ratio
- 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 front 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 with exposed coating edges)
- Life-Coat™: even harder coatings to enable an age-resistant coating with an unlimited service life – even in the most adverse environments
This new CMOS-optimised filter generation is designed to become the new standard in amateur astronomy.
