- Comet filter for the two brightest C2 emission lines at 511 and 514nm (called "Swan-Band") in the gas tail and gasplume of comets, respectively
- Blocks the adjacent OIII line, which does not predominantly occur in the tail of comets
- CMOS optimized for increased contrast
- Front-Reflex-Blocker™ hard coated and planeoptically polished – with sealed coating edges (Life-Coat™)
- Blackened edges all around
The SwanBand filter is indeed a very special filter with central wavelength at 512 nm and ≤15nm half-width - for the first time without any O III transmission. It is therefore suitable for a variety of unusual applications some of which require further investigation, whether as an "O III parallel filter" to better remove stars from the image, or as a solar filter in a previously inaccessible section of the spectrum. We would be pleased about your experience reports also apart from the comet photography.
Contrast gain for comet hunters
The Baader C2 SWAN-Band-Filter with ≤ 15 nm Half-Band-Width 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.
The Baader SWAN-Filter has got all the advantages of the CMOS-optimized Baader filters:
- CMOS-Optimized Baader Filter
- Increased contrast
- Ever more narrow passbands
- Reflex-Blocker™ coatings, for largest ever freedom from halos, even under most adverse conditions concerning aux-optics
- FWHM on each filter category carefully designed to allow for 1:1:1 exposures, matched for typical CMOS quantum efficiency and s/n ratio
- Identical filter thickness to existing standards, with utmost care for parfocality
- Blackened edges all around, with filter-lead-side-indicator in the form of a black frontside outer rim, to additionally eliminate any reflection due to light falling onto the edge of a filter
- Each filter coated individually, with sealed coating edge (NOT cut out of a larger plate with coatings left exposed read more)
- Life-Coat™: evermore hard coatings to enable a non-aging coating for life – even in a most adverse environment
