This morning at about 0900 I checked the detailed weather forecast in Astrospheric to get a sense of the prospects for imaging the full moon near midnight/at the meridian over the next two nights, and found that it doesn’t look too good. I did notice in Astrospheric that at 0900 today transparency was forecast as above average and seeing was average. Better conditions for imaging Venus than I have had recently. I also noticed that at 1000 the seeing was forecast to be below average. I hurried along to try to catch the better seeing.
The temperature was 60F when I went out at 0915, and had risen to 62F by the time that I finished the session at 1010. Surface winds were calm when I went out, but had picked up considerably by the time I finished the session.
The ASI290 was already on the Meade/G11, so I only needed to uncover, connect a battery, and go to work. Maybe 10-15 minutes from walking out the door to having Venus in the flip mirror/eyepiece, and then visible on the Firecapture display. Venus was steadier on the Firecapture display than I had ever seen it, so I got pretty excited about what result I might achieve.
While I was getting Firecapture set up for the UV first run at 0940, the surface breeze picked up a little, and I could see on the display that the seeing had already deteriorated somewhat. By the time that I got to the last IR run at 1000, and I would expect the IR to be steadier than the UV, it was just horrible. I couldn’t even tell that I was imaging a 50% phase disk any more.
The Good: I captured three runs of UV, one with the sky hump way left (similar to a DSO sky peak, just wider), one with it near the center, and one with it way right. Since Venus is only very slightly brighter than the sky in UV, this is an experiment to see what exposure produces the best results in the stacked image. I also did two runs of IR, one with the hump centered, and one with it toward the right. Venus is quite a bit brighter in IR than the sky.
The Bad: I still haven’t fixed the non-rotating filter wheel, so I had to remove it from the scope and manually turn it.
The Ugly: I checked my backyard weather station data and found that up until about 0915, the winds had been a steady 2-3mph since 0200. At that point, the winds steadily increased to about 11mph by 10am. I think that the winds aloft affect seeing more than surface winds, but maybe they are somewhat correlated. The effect on seeing was more dramatic than the change that occurred when you and I were imaging Jupiter and Saturn last summer!