It is clear tonight, after an unusual spell of foul spring weather (rain, freezing rain, snow, sleet). My plan for tonight is to begin to track down the poor tracking and guiding performance I experienced the last couple of sessions.
First, I got the ST-4 guider signals working by checking cables and connectors. I think the connector at the Gemini control box tends to lose connectivity with long sitting – probably through minor corrosion on the contacts. Working the connector in an out several times seems to have cleared it up, and the mount is now responding to guiding signals well. Continue reading
Wednesday evening I had a second chance to get outside, and tackled collimation. It was, indeed, off, and I tuned it up using CCDInspector and the QSI camera. This software makes such adjustments simple and repeatable.
It occurs to me that collimation will affect focus, so I should probably generate a fresh set of focuser V-Curves, but I haven’t done that yet.
For a test I took an hour of M1. Still no flats, so this is only dark-frame calibrated.
Trying to get this to work confirmed that I have a problem with guiding: Maxim won’t calibrate, giving the dreaded “Star Moved < 5 pixels” error. This usually means the ST-4 guide cable or connection is faulty, and I suspect that is the case here since it will calibrate and guide with Pulse Guiding, which goes over the serial Gemini connection instead of the guide cable. So looking at better guide signals is on the list for a future session.
Before that, however, I want to look at tracking – I’m getting elongated stars and think the mount should be able to do better. I’ll re-check polar alignment (since it has been 6 months and lots of temperature changes), re-check the worm clearance, and re-do PEC correction.
After a hard winter, we have finally had some clear nights with reasonable temperatures, and on evenings that I’m free, so I’m finally getting back outside. I have a bunch of work to do putting things back together and back on the air.
Re-assembling the optics, I have an AT8RC 8″ Ritchey-Chretien mounted on the G11. The AT reducer/flattener was not working well – bad distortions – and I read multiple reviews online about this device having some design problems (and apparently being recalled), so I removed it and am working direct for now. The camera is a QSI583WSG.
Saturday night was about connection and focusing, and generating the “to-do” list. Continue reading