I had grand plans for an original target this summer. Then, reality kicked in. A few technical issues and not enough clear nights at my countryside site forced me to me switch to the backup plan. Oh well, practicing scales does not hurt.
My objective was to try to pull out the fainter nebulae in the "Gulf of Mexico / Caribbean" area. I thus wanted to expose longer than my usual unguided 30s subs. I improved my PEC curve to take into account an annoying 10s period of amplitude 1-2", and my tracking error is now about 1.1" RMS, which is acceptable given the diffraction and turbulence. I typically measure polar alignment drifts < 0.5"/minute (I have to re-setup every night), so that I can safely expose 90 seconds given the 2.4"/pixel plate scale of the EOS6D/ESPRIT100ED combination. I know I'll have to guide someday, but I'm having fun that way
. With the longer exposure times, I should have dropped the ISO from my usual 3200 (lowest read noise on the 6D) to e.g. 800 to gain in dynamic range. Lots of star cores are burnt. Next time.
In the end, the limiting factor for the depth of the image turned out to be the thermal noise. We had several heat waves in France this summer, so that the images were acquired at EXIF temperatures ranging from 18 to 25°C, with most images taken at 23-25°C. That makes me want to build a contraption to cool my 6D
. No big deal, though, compared to the devastating forest fires...
I'll try to add more data taken during hopefully cooler nights later this year. In the meantime, I had to apply some pretty heavy denoising, so that the final product is still a bit grainy. I hope you like it anyway!
NB: I'm particularly happy to confirm that the 2nd modification of my 6D has indeed solved the peanut star issue caused by the initial modification, as reported in
this post.
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