2" (15 nm) C2 swan band filter - Parallel O III
- Blocks adjacent OIII line, which does not appear predominantly in comet tails
- CMOS optimized for higher contrast
- Hard-coated, plano-optically polished Front-Reflex-Blocker™ - with sealed-coated edges (Life-Coat™)
- All-around blackened edges
Contrast gain for kite 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 only lets light from the two carbon bands through and, among other things, blocks the ubiquitous stray light, similar to a nebula filter in deep sky observation. This makes the structures of the gas tail clearer even under good observing conditions. At the same time, it completely blocks the OIII line at 501 nm and below, which other swan-band filters let through. This allows even greater 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.
Just in time for the introduction of the new C2 Swan-Band filter, a bright comet, comet C/2022 E3 (ZTF), was offered as a test object. Our customer Andreas Bringmann was one of our first testers - more information in TAB Review
This image was taken from the big city and with a nearly full moon. You can clearly see the amount of "doubly ionized carbon" (carbon excited to glow radiates only in the 511 nm and 514 nm wavelengths) emitted by the comet. The filter shows the full extent of the ion cloud around a comet:
C-2022E3_ZTF passes Hassaleh at Auriga (Baader C2 Swan-Band 15nm), image obtained with Celestron EdgeHD 11", Takahashi FSQ-85ED | Moravian Instruments G3-16200 MK I, ZWO ASI6200MM Pro | 10Micron GM3000 HPS & Baader C2 Swand-Bad Filter, 2" (15nm), © A. Bringmann
The Baader SWAN filter has all the advantages of the CMOS-optimized Baader filters:
- Increased contrast, tailored to typical CMOS quantum efficiency and s/n ratio.
- Reflex-Blocker™ coatings, for increased freedom from halos, even in the most adverse conditions of auxiliary optics.
- Filter thickness identical to existing standards, with maximum care for parfocality
- All-around blackened edges, with an indicator of the filter entrance side in the form of a black outer edge on the telescope side, to additionally eliminate any reflections due to light hitting the edge of a filter, making additional front masks unnecessary.
- Each filter individually coated, with the coating edge sealed (NOT cut out of a larger plate with coatings left exposed, read more)
- Life-Coat™: increasingly hard coatings to enable a coating that will not age for life, even in the harshest environments.
