Ca K filter transmission profiles

Measurements made with a Sol'Ex spectroheliograph. Slit : 10 micron x 4 mm. Imaging lens : 125 mm focal length. Collimating lens 80 mm. Grating : 2400 l/mm.
ASI290 camera. 12-bit acquisition. Sampling : 0.0925 A/pixel.
Accuracy +/- 0.1 A on CWL, FWHM and bandwidth at 10% transmisison.

The filter is exposed to nearly perfect collimated light beam : converging light beam with a 0.5° cone (solar disk), equivalent to f-115 ratio. The surface of the filter sampled is set by the slit size (10 micron x 4 mm)

Barr Associates Ca K filter (2-cavity filter)

Alluxa Ca K filter (3-cavity filter)

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