First calibration evening

It was clear tonight and won’t be for the next few nights, so it seemed wise to get some dark time when it’s available. I set up the 80mm imaging scope to start some polar alignment.First it took rather a long time just to get all the software and hardware connected – it’s been about 8 months since I used the imaging setup, having spent available time either doing outreach or planning the observatory. Eventually I remembered what connects to what and got Maxim, one camera, and PEMPRO running.

1. Did PEMPRO mount, scope, and image scale calibration to make sure it understood the current setup.
2. Then I used the PEMPRO polar alignment feature to take drift samples with the scope pointing South and East.
   1. First pass:
      • Azimuth: 5-minute sample wants adjustment 4.6 arc-minutes East
      • Altitude: 5 minute sample, wants 3.5 arc-minutes lower
   2. Second pass, 10-minute samples
      • Azimuth: adjust 0.2 arcmin East; leaving that as good enough
      • Altitude: Lower 2.6 arc min
   3. Third pass, re-checked altitude one more time, another 10-minute sampleΩ
      • Raise 0.7 arcmin.
      • Did that, caling this close enough for now. I have both axes within 1/2 arcminute of true polar alignment, that should be more than enough, and I’ll be redoing this later after removing the mount for other work.

Then, just for the heck of it, I did a few experimental images, unguided, unfiltered, no flats, just to see what works. I didn’t use PEC because I haven’t re-trained it since adjusting the worm backlash. Focused manually with a Hartmann mask.

• M1: 3×60 dark, 5×60 Lum, 2×180 Lum. Wrong scope for this – not enough resolution – so it’s a small image, but it confirms the polar alignment is pretty good. No star trails in even the 3-minute exposures.
• NGC6888 (crescent): 3×100 dark, 5×100 Lum. Very dim object, needs much more exposure than this – barely visible. Good round stars though.
• M45 – helped me discover a new problem, another thing for the to-do list: While trying to slew around to M45, the camera on the scope hit the Gemini electronics panel, which is in an unusual position because of the way it mounts on the pier adaptor.

  To-do list item: make some angle brackets to move the panel to the main pier body somehow, so it doesn’t stick out as far. Be careful not to over-extend the rather short reach of the DEC motor cable.

Ok, I’m cold – shutting down. About 4 hours outside yielded about 3.5 hours of useful work – I love having this permanent structure.