Antlia 1.25 Inch CaK II 3 nm Filter for Solar Photography in Calcium Light

Antlia 1.25" Calcium Filter for Solar Photography

The filter allows solar photography in the calcium line around 393.3 nm. In calcium light, sunspots are imaged similarly to white light, but with more contrast. The flares, solar granulation, flares and even bright prominences in the edge region of the "solar disk" become visible to the photographer.

Never look at the sun only with the CaK line filter. A lot of invisible but harmful UV radiation enters your eye. The filter is intended exclusively for photography.

We suggest the use of a monochrome astro camera because it does not have a UV/IR block filter, i.e. it can be light sensitive up to the UV range. Also the Bayer filter of the color cameras darkens light noticeably below 400 nm, apart from the fact that three quarters of the pixels are generally not designed for shorter wavelengths due to the matrix.

Important note: The photographic solar filter film from Baader is necessary for light attenuation. The visual film (16x denser) would darken the image of the sun too much. For refractors without correctors, you can also use a Herschel wedge instead of the film, whereby the often built-in ND3.0 filter may have to be replaced by an ND1.8 filter.

Images by a customer

Our customer Stéphane Langlois from France took nice images with this filter, using a non-aluminized 200 mm Newtonian on a Sky-Watcher AZ-EQ6 Pro mount and a ZWO ASI533MM camera:

This image shows the solar disk as a single object. The large image shows more detail than the following one.

The exposure time of the individual images of only 0.3 ms prevents blurring due to seeing, even even with a total exposure time of 30 seconds.


This image is a comparison between (from left to right):
Baader Solar Continuum Filter, Baader K-Line filter (8 nm FWHM), 3 nm CaK filter by Antlia.

The increase in contrast is remarkable.

We congratulate Stéphane Langlois on his impressive results!

Special image by a customer

Stéphane Langlois also used this filter to take a picture of objects that would normally require a much more expensive filter:

This heavily exposed image shows the solar disk as a uniform disk, but you can see some prominences! The ones at "3 o´clock" and "4 o´clock" are striking, but prominences can also be seen at "half past seven" and "half past ten".

You can recognize them much more easily if you click on the image to display it in large size.


In this image, Stéphane Langlois has marked the prominences, as the fainter ones are not so easy to recognize. Again, a click on the image will help.

In the Solarfilter for H-Alpha and Calcium section you will find extremely narrow-band H-alpha filters, with which you can see the prominences much more clearly and also the filaments on the solar disk that are invisible on the calcium image, but these filters are practically only suitable for refractors and are considerably more expensive.

We congratulate Stéphane Langlois on this amazing result!

Safety informations: PDF Download