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I have wrapped an Astrozap, dew heating band around the iStar objective and D-ERF filter cell ready for the next imaging session. Yje three thumbscrews of te filter cell both hindered and helped The 4-port, HitechAstro dew heater controller is now tied up beside the mounting to reduce the considerable changes in cable tension. Why no tab, screw eyes or hooks for support on these devices?
I'm using black cord to tidy up all the trailing leads. Better than zip ties. Which have to be cut off when they don't suit the occasion. Cord can be easily undone, moved, retentioned and retied as many times as desired.
I plan to make a slip-on, tubular, closed cell foam dewshield, to act as a dual-purpose insulator. This will enclose the heater band to further aid dew removal. The dew heater will not be running when I am not in the observatory. So I will be able to carefully monitor heat build up and its effects on dew removal.
Here's a good choice of camping mat material for a dewshield: The aluminium coating will slow thermal radiation to the cold night sky. While the foam will reduce convection. I like the look of the alu coating and the foam looks rough enough to block grazing reflections. The foam could even be given a quick coat of matt black paint inside if needed.CAMPZ foam Mat black/alu | CAMPZ.dk
I can slip a thermometer probe on a lead in there. For greater accuracy than my human touch. It is not easy to push a finger inside the taught heater band once it safely tightened in place. Opening the band to check how warm it might be will only increase heat loss.
The D-ERF filter cell has three large clamping knobs. Which would make fitting a metal dewshield slightly difficult. As it would require trimming around these knobs. Besides, a metal dewshield will act as a conductor and draw more heat out of the objective cell and the lens overnight. I shall make a lightweight, insulating plug of foam to close off the dewshield overnight. The nylon threads of the clamping knobs could be trimmed a little to reduce their protrusion. Some sort of glue for the foam would be good to make a much neater job than tape or string. More on this tomorrow.
Thursday 20th 38-44F, Heavy overcast with rain and wind. Imaging looks extremely unlikely. Though such weather can be thought of as a useful goad to making more progress on construction and set-up. It was a horrible day so I worked on other projects indoors.
Possible sunshine tomorrow. But then, they promised sunshine today and there was none.
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