White light solar imaging with a low cost aluminised PET solar filter.
A low cost aluminised PET (PolyEthylene Terephthalate) filter was mounted over the objective of a William Optics Zenithstar SD doublet APO, 66mm, F=388mm refractor. An SVBONY SV705C CMOS camera was placed at the focus.
The scope was fitted with a Pegasus FocusCube version 2, a Raspberry Pi computer (running an INDI server) plus a Goodmans power supply for the Pi. The hand controller was connected to the Raspberry Pi. The system was mounted on an AVX GOTO mount which was, as usual placed on marks on the concrete to provide an acceptable polar alignment.
AstroDMx Capture, via the INDI server on the network, sent the scope/mount to the Sun. An arbitrary Region Of Interest was drawn around the Sun. AstroDMx Capture controlled the Pegasus motor focuser and brought the Solar image preview to focus.
AstroDMx Capture captured a 5000-frame SER file of the whole solar disk.
The best 20% of the frames were stacked in Autostakkert!, wavelet processed in Registax 5.1 and post processed in the Gimp 2.10. The filter produces an essentially white image which was given a yellow hue by adjusting colour temperature in the Gimp.
Solar image
The filter needs to be tested further, but it performed quite well and produced an acceptable image with the SV705C camera
