Baader Calcium GEN-II 1¼" Filter (Calcium)

As an unstacked single filter, shows the finest solar details in calcium-K (Cak) light
    For photographing the sun only in conjunction with the included AstroSolar photo film ND3.8 or a separately available Herschel prism
    Increased contrast tuned to typical CMOS quantum efficiency and s/n ratio
    Reflex-Blocker™ coatings, for the greatest possible insensitivity to retro-reflection from the nearest auxiliary optics, even under the most adverse conditions - with sealed coating edges (Life-Coat™)
    Identical filter thickness to existing standards, with the utmost care. Homofocality
    Filter individually finely optically polished and coated, with sealed coating edge (NOT cut out of a larger plate - with exposed coating edges, see more here)
    Delivery includes AstroSolar photo film ND 3.8, format: 200 x 290 mm - for pre-filtering sunlight
    The calcium filter Gen-II must NOT be used in the beam path WITHOUT pre-filtering.
    Visual observation is not possible with the calcium filter because the eye is practically blind in this spectral range. Never point the telescope directly at the sun using only the calcium filter (without an additional attenuation filter).

Calcium GEN-II Filter 1¼"

The calcium GEN-II filter opens up a view of 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 over the entire surface of the sun, which precedes the formation of sunspots, is also visible, as are supergranulation cells and Ellerman bombs.

The calcium line is at 394 nm and therefore in the near UV. Therefore, observing the sun is only possible photographically! Never use the filter visually as the eye is blind to the harmful UV radiation but is damaged by it.

The filter achieves the best results with a monochrome camera (which is more sensitive in this spectral range than a color camera) and with pure reflecting telescopes (since particularly bright lens telescopes are not optimized for this edge region of the UV spectrum). However, many refractors still produce sharp images even in the calcium window; With unmodified DSLRs, extremely long exposure times may be necessary because many camera models do not allow transmission below 400nm.

All calcium filters require an additional solar filter in front of the actual calcium filter. So that you can start observing quickly, the Baader GEN-II comes with a sheet of AstroSolar photo sun filter film OD 3.8, 20x30 cm (#2459278, € 34) for building your own lens filter. Alternatively, ready-made BDSF: Baader Digital Solar Filter OD 3.8 (80mm - 280mm) are also available. It is also possible to use suitable refractors behind a Herschel prism. The ND3 pre-installed in the Herschel wedge can be replaced by a weaker filter to enable shorter exposure times. Corresponding filters are already included in the Baader Cool-Ceramic Safety Herschelprism 2" Mark II Photo (#2956510P, € 645,-).

The Calcium GEN-II replaces the previous K-Line Filter 1¼" (stacked) # 2458355. Thanks to modern manufacturing techniques, a single filter now achieves better quality and a narrower half-width of only 5 nm instead of the previous 8 nm; stacking two filters is now possible no longer necessary. This also makes it possible to use the filter in standard filter wheels/drawers; the low-profile filter holder is only 6 mm high when screwed in.

To use the 1¼" filter on cameras with a 2" connection, you can either use a filter drawer like the Baader UFC system or a filter wheel. It can also be screwed in front of many Barlow lenses and in all 1¼" receptacles such as Baader plug-in connector 1¼" / T-2 with safety kerfs (#2458106, € 31,-). The adaptation between two T-2 threads is possible with the combination of double T-filter holder 1¼" (T-2 component #31) (#1508030, € 33,-) and T-2 internal thread ring 10mm (#2958110, € 29, -) possible; for cameras with 2" filter thread, the M48 threaded ring on T-2 (T-2 component #29) (#2458110, € 22) is also required.

The Baader Calcium GEN-II offers all the advantages of the CMOS-optimized Baader filters:

    increased contrast, tuned to typical CMOS quantum efficiency and s/n ratio
    Reflex-Blocker™ coatings, for the greatest possible insensitivity to retro-reflection from the nearest auxiliary optics, even under the most adverse conditions
    identical filter thickness to existing standards, with the greatest care regarding. Homofocality
    blackened edges all around, with filter front indicator in the form of a telescopic black outer edge to additionally avoid any reflection from light falling on the filter edge
    Each filter is individually finely optically polished and coated, with a sealed coating edge (NOT cut out of a larger plate - with exposed coating edges, see more here)
    Life-Coat™: even harder coatings to provide an aging-resistant coating over an unlimited service life - even in the most adverse environments

    MANUFACTURER Baader Planetarium
    ITEM NUMBER (#) 2961590
    EAN CODE 4047825048783
    NET WEIGHT (KG) 0.108
    PASSAGE AREA CaK-II
    FILTER THICKNESS (WITHOUT MOUNT) 2 mm
    HWB (HALF WIDTH) 5nm
    ZWL (CENTRAL WAVELENGTH) 394 nm
    COATING (ANTI-REFLECTION) dielectrically coated, optically polished
    SPECIAL FEATURES for photographic use only behind another solar filter
    FILTER SIZE 1.25"
    TYPE OF USE Sun
    FILTER COLLECTION mounted (LPFC 6mm)
    FILTER TYPE Narrowband
    INDIVIDUALLY OR IN A SET?    Single filter
    FILTER SHAPE round