Antlia CaK 3nm 393.3nm filter review
The Sun is the only star where amateur telescopes can be used to view or photograph details in the stellar atmosphere. In 1814, the German physicist, optician, and inventor Joseph Fraunhofer first observed lines in the spectrum of the Sun and assigned a nomenclature to the most noticeable lines. Some of his notations are still used today. There are special telescopes and light filters with which you can photograph the Sun in various spectral ranges. I decided to purchase one of these filters for photographing the Sun in the calcium line (CaK, or K-line) – Antlia CaK 3nm 393.3nm 1.25″.
IMPORTANT!
1. Antlia CaK 3nm 393.3nm filter is NOT INTENDED FOR VISUAL OBSERVATIONS! IRREVERSIBLE LOSS OF VISION IS POSSIBLE! FILTER FOR ASTROPHOTOGRAPHY ONLY!
2. Antlia CaK 3nm 393.3nm light filter cannot be used without first filtering sunlight, otherwise you can damage the filter and camera! It is necessary to use an aperture filter (I recommend Baader AstroSolar Photo ND 3.8), or a Herschel wedge + an additional ND filter.
The filter is available only in a 1.25″ form factor, which is quite enough for shooting the Sun with most lunar and planetary astronomical cameras. The filter is supplied in a very impractical magnetic box that tends to open up.
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