The scope used was a William Optics Super Zenithstar 81mm ED Doublet APO refractor at f/5.5 with x0.8 flattener/reducer fitted with an Altair magnetic filter holder version 2.
An SVBONY SV605MC cooled, monochrome CMOS camera was placed at the focus of the telescope which was mounted on a Celestron AVX EQ, GOTO mount. An SVBONY SV165 guide-scope fitted with a QHY-5II-M guide camera was mounted on the imaging scope. PHD2 auto-guiding was controlled by a separate Linux laptop for convenience.
AstroDMx Capture controlled the mount via an INDI server running on a Raspberry Pi computer. The hand controller was connected to the Raspberry Pi and AstroDMx Capture communicated with the INDI serve on the Pi via the local network.
AstroDMx Capture sent the scope/mount to a bright star; a Bahtinov mask was fitted and focus was checked and adjusted if required. This had to be done with each of the Red, Green and Blue filters. The RGB filters were a set by Pegasus Astro and are not quite parfocal.
As part of a test of the fully automatic finding and centering via multiple plate solves if necessary, to achieve a user-specified pointing accuracy. In this case a value of 2 arcseconds was specified and the scope/mount was sent to M13. M13 was automatically centred in the field of view.
In turn, AstroDMx Capture captured 50 x 25s exposures with R, G and B filters, being sent to a bright star for Bahtinov mask focusing after each filter change, and returning to M13 by the fully automatic process.
Dark frames were captured and Flat fields were also available. The Red data were calibrated, registered and stacked in Deep Sky Stacker. The stacked Red image was then used as the reference image for stacking the Blue and the Green images. The results were perfectly co-aligned Red, Green and Blue stacked images.
The stacked images for each colour channel were stretched a similar amount in the Gimp 2.10. The channels were combined into an RGB image in the Gimp and the RGB image was further processed in the Gimp, Neat Image and GraXpert.
RGB M13
