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.
Cloudy for the last week, and forecast cloudy tonight. Went out during the day and did a bit more work in the dome, installing dew heaters on the primary scope, guide scope, and finder. Winter’s cold is about to arrive (-16 tonight), so I wanted the dew heaters in place to fight frosting on the rare nights it’s clear and I am willing to brave the cold and go outside. Both tomorrow night and the next night are forecasting possibly clear (I’ll believe it when I see it). Full moon too, but narrowband imaging will still be possible.
I had hoped to do some PEC testing, colour calibration, and trial imaging tonight. The sky cleared around 5PM, on schedule, and was supposed to stay clear until about midnight. Poor transparency, but no moon – it’s ‘way past 3rd quarter, and won’t rise until later.
First, I re-did another test of Periodic Error using PEMPRO, about 6 worm cycles of data. Then calculated a PE correction curve and uploaded it to the mount. With this curve in place I did another test with Periodic Error Correction turned on, and got residual error of +/- 1 pixel – about as good as I can hope for, and easily correctable with guiding. Next, I imaged a G2V star in RGB to help calibrate my colour filter exposure times.
By the time I did this the sky was getting quite hazy, so I’m not sure these numbers will be accurate, but they’ll be a start. By the time I finished the G2V captures, the sky had 90% clouded over – at only about 7:30 PM. That was disappointing, only 90 minutes of clear sky and none of it very good. So, I closed down. No images to share tonight. It’s very frustrating weather. At least with the Skyshed POD it’s only a matter of a couple of minutes to start and stop a session, so it’s possible to get some use out of even these short sessions.
It’s finally clear out. Not really clear, not a good sky for imaging, and only a couple of days past the full moon. But there are enough stars visible to at least capture some data for periodic error testing and programming.
So, I just spent 1/2 hour outside opening the dome and getting things connected. (Startup is still delayed by an annoying problem with Windows Vista not remembering where certain drivers are, making me manually reinstall them at each boot.) Got the scope going, calibrated, and focused, and started a PEMPRO data aquisition run, then came inside to monitor by VNC. I plan to gather a good hour’s data, about 15 worm cycles, then do a mount program, then do a test of the improved tracking. Continue reading →