Yesterday afternoon the forecast was suggesting that I would have average transparency and above average seeing at about 0300, which for me were better conditions for planetary imaging than for DSO imaging. Being anxious to try out the UV/IR cut window, I started getting ready for planetary imagine. First, I replaced the AR window in the ASI290 with the UV/IR window and “cleaned” my optics. I also put the Meade back on the mount, and then I reset the polar alignment that was perturbed by changing scopes. Dew was already starting to form as I was polar aligning, so I left the dew heater on high hoping to find dry optics if I was able to image.
After polar alignment, I slewed to Deneb to check collimation, which was good, and for a goof I slewed to Albiero to see what kind of star image I could get with the ASI290. I shot one RGB run at 60s/filter.
My final prep was to set an alarm for 2:45 and hope for the best.
When I got up and checked the sky, and half-way hoping for clouds so that I could go back to sleep, I found that the sky was mostly clear with some residual clouds moving off to the east, so I went outside to image. While I was at the scope from 0300 to 0520, the temperature fell from 68 to 66 degrees. The dew point was tracking about 2 degrees lower than the temperature, and the relative humidity was 98%. There was dew on the optics except for a thin band about 1 1/2” wide around the outer edge of the corrector plate. There was an occasional slight breeze. I was comfortable in t-shirt and shorts for a while, but started getting chilled toward the end.
I was able to acquire Jupiter rather quickly. I was happy to see that it was fairly steady, and In spite of the dew the image seemed clear, and was easy to focus in red. The GRS was just about to rotate out of view to I quickly shot two RGB runs at 30s/filter to capture. After fine turning my exposures (gain 350, exp 15ms), noticed that Jupiter had crossed the meridian, so I executed a meridian flip before shooting 11 RGB runs at 30s/filter. I then changed my exposures to gain 400, exp 6ms so that I could compare the two captures. In both cases I kept the histogram down to 50% to get my frame rate up to about 70 fps.
Next I slewed to Mars and captured 10 RGB runs at 30s/filter with gain 400 and exposure of 15 ms.
The dew situation had not improved by the end of the session. I was headed back inside by 0520.
In hindsight, I have for some time been pretty sure that there would come a time where I would need the blow dryer to clear my optics. That time was tonight and I wish that I already had the dryer. My optics cleaning didn’t go so good. I was difficult to find a clean spot on the display large enough to accommodate Jupiter.I was very careful in my cleaning, so I don’t know why dirty optics was a problem.
Order blow dryer