Rho Ophiuchi at Canyon of Eagles

This evening was another Austin Astronomical Society members-only star party at Canyon of Eagles. I went with the goal of trying to re-image the Rho Ophiuchi Nebula. My last attempt, in August 2013 using the same camera and lens, was a disappointment due to image noise.

This time, I used my homemade cooler box and made sure I took a series of dark frames. My ISO and aperture settings were the same as last year, as was the total integration time. However, in an attempt to further reduce noise, I halved the individual exposure times to 300 seconds, enough to detach the histograms from the black-point. With an ambient temperature of about 85F, I was able to cool the camera enclosure down to a steady 66F. The noise had the same diagonally-banded characteristics but at a lower level. This allowed me to boost the shadows more before the noise became problematic. All image acquisition control via Astro Photography Tool.

I am considering purchase of an adapter to connect my QSI-540ws directly to the Canon lens; there is still no comparison between the noise level of the astronomical camera and a DSLR.

Rho Ophiuchi - Canon 60Da / Canon EF 70-200mm f/4L - 28 x 300s, ISO-800, 200mm, f/4.

Thanks to Dave and Ed, my neighbors for the evening, for sharing visual views through the large Dobsonian.