Have been working up the first element of a galaxy imaging system – a Starlight express 694 camera. Am still waiting on a coma corrector and for the EQ8 to appear and have not yet finally decided on the scope, so initial testing was with an 8 inch f4 Newtonian on a tripod mounted EQ6, without coma corrector and with a 50mm guidescope.
The EQ6 was out of its comfort zone at 1.17 arcsec per pixel in wind. Modelling had shown that the optimum sub (for maximum SNR) was 2 minutes, but that the system should still be effective with subs down to below 20 seconds, so short subs were used to help overcome mount deficiencies. The attached image is a native scale central crop with a bit over 30 minutes total imaging time using both 20 and 35 second subs in about 2.7 arcsec FWHM seeing+tracking. The only processing used was a stretch and modest deconvolution/sharpen to remove the worst of the remaining tracking excursions (decon pushed some stars into saturation and upped the apparent noise). No calibration (dark, bias, flat) of any sort was used and the dark current can be seen as a few horizontal drift lines from individual warm pixels (deliberately retained in stacking) – that really is the total extent of obvious thermal noise straight off the chip. There is a large amount of headroom with short subs and only three stars in this image reached saturation. I clearly needed more than 30+ minutes of data, but clouds and wind ruled that out – the results are still promising for first light.
Overall, am very pleased with the camera - works exactly as advertised. The modelling was also spot on and accurately predicted how it would perform in a system. Very short subs are practical – sensitivity is high and noise is very low. Image scale is OK with the 200mm f4 and will be about right with the final scope (10 or 12 inch f4). This fairly crudely processed technical image is the first step towards the new system – there will be lots of hurdles to come, but so far so good….
Thanks for reading. Regards ray