Baader C2 Swan-Band Filter (15 nm) O-III parallel - 1.25" - for observation and photography

Baader 1.25" C₂ Swan-Band Filter (15 nm) O-III parallel, for photography and observation

Enhances contrast when observing comets

The Baader C₂ Swan band filter with 15 nm half-width isolates the two C₂ lines at 511 and 514 nm.
These two emission lines, called Swan bands after their discoverer, dominate the spectrum of the gas tail of a comet in the visible range. The filter only allows the light of the two carbon bands to pass through and blocks the omnipresent scattered light, similar to a nebula filter in deep-sky observation. Structures in the gas tail thus become clearer even under good observation conditions. At the same time, it completely blocks the [O III] line at 501 nm and below, which other Swan band filters allow to pass. This allows an even higher contrast, and comets with a gas tail can be distinguished even better from comets dominated by a dust tail (for which a Swan filter only provides a slight increase in contrast). For ambitious comet observers, a Swan band filter is part of the basic equipment.

Comet C/2022 E3 (ZTF) was photographed from a large city and with an almost full moon. You can clearly see the amount of doubly ionized carbon (wavelengths 511 and 514 nm) emitted by the comet. The expansion of the ion cloud is very clearly visible.






The Baader SWAN filter offers all the advantages of the CMOS-optimized Baader filters:

Increased contrast, matched 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 greatest care taken with regard to homofocality

blackened edges all round, with filter front side indicator in the form of a telescope-side black outer edge to additionally prevent any reflection from light falling on the filter edge

individually fine-optically polished and coated, with sealed coating edge (NOT cut out of a larger plate with exposed coating edges as a result)

Life-Coat: even harder coatings to enable an ageing-resistant coating over an unlimited service life, even under the most adverse conditions

Safety informations: PDF Download