It was clear last night, the first truly clear night in a long time, but very cold. Ambient temperature was -18c. I opened the dome and started things up, to have a series of mount problems. Guiding was very ragged, jumping around a lot.
I suspect this was Periodic Error Correction being unhelpful – that the PE curve has changed since I adjusted and rebalanced the mount, and PEC was now working against me. I used an hour to gather new PEC data but never did get to the point where I was happy with the correction. However, the uncorrected PE was reporting as fairly small (+/- 3), so I decided to just do some guided capture without the PEC. Turns out that worked very well.
This is the time of year that B33 (Horse Head) is visible over the house, between the trees, so I started that for the season. Unfortunately the previous problems meant that I only had an hour left and, sure enough, after 55 minutes image capture started to fail as the target began to encounter tree branches.
So, just as a sketch, this is the start. This is 55 minutes of Red light, as 11 5-minute subs. Guided but no PEC – I’m quite pleased with the guiding. More light and other colours as the season progresses – it’s forecast cloudy again for several nights now.
It was a cold -18 last night, but the first clear night in ages, so I bundled up and went out to the observatory to do some imaging. With a nearly full moon, narrowband imaging was the best option since it is nearly immune to light pollution, so I set up a nice frame of the Barnard 33 (Horse head nebula) and NGC2024 (Flame nebula) area and took 1.5 hours of exposure in Hydrogen Alpha light.
I’m very pleased with this result, considering the conditions. I plan to add colour later when skies permit, and use this H-Alpha either as luminance or to supplement the Red.
The exposure would have been slightly longer but I bumped my head on the scope during the last 15-minute subexposure, ruining it. Serves me right. I also got an error message from the Gemini system right at the end of my session (“motor stalled”), and must investigate that during daylight. I’m guessing that the cold made things stick enough that the motor got tired when I started slewing around the sky after the main session. I’ll do a motor health check in the next day or so, in daylight.
It’s clear tonight and no moon, temperature about 0 C. I used the evening to start testing out the wide-field imaging train.
I eventually plan to image with the C9.25 and, for that, will use the Van Slyke off-axis guider to avoid differential flexure of a guide scope. I tried that tonight with the SV80 refractor. It didn’t work – there isn’t enough back-focus in the refractor to hold the large VSI OAG. I tried the old Mead OAG and it works ok, except I couldn’t find a way to attach it to the filter wheel – so I did some tests of straight monochrome imaging and OA guiding. Continue reading