A Bresser Messier AR 120xs f/4.51 achromatic ED refractor configured as a Ca K-line telescope

We configured a Bresser Messier AR 120xs f/4.51 achromatic ED refractor fitted with a skywatcher motor focuser and mounted on a Skywatcher Solar Quest solar finding and tracking mount, as a Ca K-line telecope by attaching an Antlia Solar Herschel Wedge with an integral 3nm Ca K-line filter. An Altair 678M camera with 3840 x 2160 pixel resolution was used. This gives a Dawes Limit of 1.14 arc/sec, a field of view of 0.96 x 0.54 degrees and a resolution of 0.9" x 0.9"/pixel. AstroDMx Capture was used with live flatfield correction to capture two overlapping 1500-frame SER files. The best 70% of frames in each SER file were stacked in Autostakkert 4, stitched with MS ICE, wavelet sharpened in waveSharp 3 and finished in Gimp3.

Bresser Messier AR 120xs f/4.51 achromatic ED refractor fitted with a skywatcher motor focuser and mounted on a Skywatcher Solar Quest solar finding and tracking mount

Antlia Solar Herschel Wedge with an integral 3nm Ca K-line filter

The Sun in Ca K-line light monochrome image

The Sun in Ca K-line light colourised image

Although the A Bresser Messier AR 120xs is a fast achromat, the fact that it is dealing with only a 3nm bandwidth in the UV means that the Ca K-line light is not subject to chromatic aberration when used in this configuration. Substantial amounts of the chromospheric network are visible.