My objective for this session was the same as last session, which was to image an easy target early as a warm up for Omega Centauri and maybe a couple of more targets that are not accessible from more northerly latitudes. As was the case for WSP Night 2, high winds made accomplishment of these objectives impossible.
I used the same setup as the previous session – G11/NP101/ASI6200. I also accepted the polar alignment from the previous session. I was not able to complete guide camera focus or calibration the night before, but I was able to work through them this time.
After trying multiple methods, PHD kept throwing calibration errors. I eventually accepted the calibration and moved on. I was getting RMS errors of about .60” for Dec (2x what I usually get) and about 3.50” for Ra (about 4x the usual). The scatter diagram confirmed this result, and suggested that stars would be highly elongated along the Ra axis. Even the shortest duration test shots further confirmed this result, so I gave up trying to image.
Next I tried imaging with the EOS 60Da. In setting it up earlier I discovered that the adapter that mates the camera to the ball mount on the wind up tracker was not in the camera bag. I decided to try a series of short, unguided exposures with 60Da and the 14mm f/2.8 lens. I pointed the camera at the intersection of the south point on the horizon and the meridian, and set up a series of 8-second exposures at 9 minute intervals. The images (all were individual, unstackable frames) were interesting in that I could watch the progression of the southernmost viewable objects rise, culminate on the meridian and set again. Passing clouds and heavy winds resulted in images of such low quality that I will not publish them.
There are a lot of objects with NGC and C designations in this area. Most were not visible and even the best ones were very low quality. I continued imaging until Eta Carina culminated at 0134, at which point Omega Centauri came into view from the east side of the frame. While it was neat to watch the progression, the images were nothing to look at.
The winds had picked up quite a by the time I was shut down at 0145.
I cannot be sure, but I believe that the flexure of lightweight tripod caused by high winds and a heavy payload was the source of my guiding problems. I purchased the GM8 mount with the lightweight tripod to support the NP101 scope. I think that even this setup would not have guided adequately in the winds that I experienced during this session. To make matters worse, my equipment stack on top of the lightweight tripod for this session included the G11 (2x the GM8 weight), a set of dovetail plates and rings that weigh about 10 lbs, and the camera/focuser/OAG package on back of the scope weighs nearly five pounds. I have successfully used this combination for imaging in non-windy conditions, but it was not able to hold the scope steady under last night’s winds. I checked the scope’s stability with a gentle shake this morning, and it was obviously flexing.
As a remedy, two things come to mind. First is to always use the heavy weight tripod that I bought with the G11 to carry this payload but even this tripod might not be able to steady the scope under the winds encountered last night. The next item that comes to mind is an observatory tent. An Explore Scientific sales rep stopped by and mentioned that they sell one for about $260. This would open the range of conditions under which I can image.
I encountered no other issues that require attention today.