The CSC predicted clear skies last night, but reality disagreed, and it was completely overcast. Tonight seems better – the sky is clear and steady, and it’s dark earlier because today is the day we went off Daylight Savings time. It’s cold out – 1 degree Celsius.

Yesterday during the day I adjusted the RA worm gear, increasing the slack to the OVision specs, hoping that will improve the Periodic Error of the mount, so tonight I am doing a PEMPRO run to get new PE data and generate a new PE Correction curve. I’ve just started a 15-minute data gathering run, and am typing this from inside while the data collect.

The initial run gave under +/- 4” error, with a reasonably repeating curve (which already seems better than the rather ragged guiding track I was seeing the other night, before adjusting the RA slack). Better, the frequency plot of the error showed it is largely periodic on the worm cycle, so it will respond well to PEC. So I uploaded a calculated PEC set to the mount, and did another data gathering run with PEC turned on.

Oops. The new run had a weird spike in data right at the start, and I realized that I had slewed the scope but then not taken the slack out of the RA gear. So it took until the RA drive “crossed the gap” of the RA backlash before accurate tracking was underway. Lesson learned, and I started the run again.

Great results – PE with correction is now showing at +/- 1.1”.

With these encouraging results in hand, I tried a quick couple of test images on some conveniently-located subjects. M2 was almost in the field anyway, so I started there. A quick Bayer conversion of the output from the one-shot colour camera reminded me that I haven’t yet taken G2V calibration data for colour balancing.

So, I used TheSkyX to locate a nearby G2V star and took a bunch of exposures of it, for later calculation for colour balancing.

Then I ended the evening by gathering some more exposure time on M27, 100 minutes in 10-minute subs. Watching the frames collect, I’m very pleased with the guiding now. The ragged jumping around of the other night is gone, and the stars are showing up nice and round.

I have a collection of dark frames for this chip temperature (-20) already, and will add a few more to the set. Then, I’ll do flat frames on a future cloudy night – it’s cold out and when these exposures are done I’ll call it a night. Supposed to be clear tomorrow night and, if so, I will add another 100 minutes of data.

Update: captured a bunch of flat and bias frames on the following evening, and the attached image is updated with calibration.

Data capture in progress, showing pretty good guiding: