13 Mar 2014. Despite quite a lot of moonlight, I ventured out to play with my PicGoto and to try and see if my focus was drifting as my scope tube cooled down. I first tried Bhatinov Grabber and focusing with the Bhatinov mask. I couldn’t get the Grabber to work, but I did focus fairly well (I thought). I used the PicGoto from Sirius to get to my first target, M47, and commenced imaging. After an hour I stopped and invoked Nebulosity fine focus and found the focus was way off! So it does look like I have significant thermal drift. After refocusing I acquired another 37 subframes. I stacked and processed the two sets separately with otherwise the same parameters, and the difference is obvious. Periodic focus checking is going to become part of my imaging workflow. I also imaged the M3 globular cluster after this and got an image I think looks pretty good (but you'll have to go to Astrobin to see that one). My PicGotos were right on every time. Now it looks like even though there is some good weather again, I’m going to have to wait for the Moon to tone itself down a bit before I go back to deep sky targets.
I’m expecting some electronic components to arrive in the next day or two that will allow me to build a voltage switcher for the PicGoto so I don’t have to drive the motors at 12 V when all I’m doing is tracking the sky; this should prevent the RA motor from getting hot. Hopefully my next entry will describe this.
This is the poorly-focused image. I think focusing degraded as the optical tube cooled.
I think the focusing is tighter in this image, in which I used Nebulosity's "fine focus" feature to fix things.
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