CG5 Mount Assessment and Weather Balloon

Equipment configuration was CG5 with Vixen 80. Imaging and guiding package was 60Da main camera and ASI290MM guide camera on a ZWO OAG. Mount and guide camera were attached to and controlled by PHD2 software on Doug’s computer, and the main camera was attached to my computer and controlled with BYE software.

A from-scratch setup began in earnest shortly after sunset, and I noted the time as 2042 as setup preparations were in the final stages. Temperature was 68.7F and Dew Point was 51.4F. There were no winds to speak of, but contrails and high thin cloud bands streaked the sky. We were hopeful that they would blow away. The Astrospheric forecast was for average transparency and below average seeing. The dew threat was low because the current temperature and dew point plots were fairly well separated and were not forecast to converge until around sunrise.

At 2045 Doug noticed a very bright object in the sky located about 3-4 degrees southeast of the Moon. It appeared motionless and unchanging in brightness until suddenly disappearing at 2050. Duration of the observation was 5 minutes. We discussed possible stars and could come up with nothing that would be nearly that bright in that location. We consulted Stellarium and it did not show anything located in this area. I reported our observation to HAL, and several guesses came in. Justin Taylor reported that he observed it for 20 minutes, and that it appeared not quite circular when viewed with binoculars. Of the guesses, we rejected satellite,  ISS and iridium flare, because of the duration of the observation and it’s seemingly stationary position. We rejected swamp gas, because it was way to bright. Weather balloon was the guess that seemed most plausible. John Nagy later provided an email with Sonde weather balloon tracks showing them launching from NWS Sterling and coming near our area. The balloon would have been about 100,000’ altitude when we observed it, and the sun would have set below the horizon at 2030. The high altitude and setting sun explain how it was brightly lit, and why it suddenly disappeared as the Sun sunk further below the horizon. Weather balloons can be tracked here:

Initial polar alignment was accomplished with compass and inclinometer apps during set up. Polar alignment refinement began at 2115. There was some difficulty in acquiring Polaris as cloud bands passed. It was eventually bright enough to see and was visible just inside of the CG5’s alignment scope FoV, probably as the result of a more precise initial alignment we did with the apps.

At 2137 we began focusing the main and guide cameras. We were able to easily find stars, but achieving good FWHM numbers proved a little difficult due to passing cloud bands. The final main camera focus position exposed about 35mm of the bright portion of the Vixen draw tube.

By 2215 we moved on the PHD2 to complete calibration, further polar alignment refinement, and a guiding assistant tool run in order to prepare for the actual mount assessment. Most of the difficulties we experienced  could be attributed to interference by the passing clouds. We decided to do a 2-star alignment in the event that it would be useful in driving the scope around for other activities. I think that it is safe to say that we did not rely on the alignment and we were tempted to avoid other useful adjustments that might have perturbed the alignment. The workplan was to do the next polar alignment refinement with the PHD PDA tool, but finding ourselves at the conjunction of the meridian and equator after calibrating, we elected to keep the telescope in that location and use the drift alignment tool instead of going back to NCP for a PDA refinement. A good polar alignment was quickly achieved with the DA tool. We saw brief periods of very good guiding, and some very bad. The guiding assistant tool reported that the PAE was 37’, but we did not believe that to be true. The backlash measurement failed because there was no South guiding response.

We began the actual mount assessment by taking guided exposures of varying durations with the main camera at 2347. We saw some very good and some very bad main camera exposure results. We were not able to reach any conclusions about the mount’s guiding performance because the clouds had increased, and PHD dropped the guide star a couple of times.

.We concluded the session at 0045. The temperature was 62.8F and the dewpoint was 55.8F. There was no dew on metal surfaces. Clouds were considerably thicker and covered much of the sky.

I think that we correctly assessed during the session that any results from this session would be inconclusive due to the clouds. We mentioned that we were surprised to be able to get the result that we did given the adverse cloud situation. That notwithstanding, the session was very useful in that we had a great practice run with the actual equipment and with the tools that we will be using. Next time we should be able to get through the work plan more quickly, which will open possibilities for experimentation as ideas come to us, or maybe even to test with a second scope.

Two thoughts that came to me during the session that leaked out before I could communicate them were to experiment with uni-directional Dec guiding, and try various exposure settings. We can try those next time.

This makes me think that maybe we were doing unidirectional guiding, and that was reason the backlash measurement could not detect a south response. Would you mind checking? Open PHD2 and navigate to Top Menu/Guide/Advanced Settings/Declination and check the Dec guide mode. Auto is the usual mode, but I am thinking that you might find it set to North only. We can experiment with Auto and South only next time.

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