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From the clear sunny day of the 18th:
The Lacerta 2" Herschel prism has reached 100F after many hours of the 7" tracking the sun under cloudless skies. Hot enough to feel very warm but not unpleasantly hot. It would cause no injury if bare skin were left in contact.
The dome is at 58F inside, at the top of the pier [in shade] to the 48F in deep shade outside. Which is measured, in free air, between the joists, under the veranda on the north side, to avoid ever receiving any sunshine.
Pointing my [inexpensive] laser guided thermometer "gun" at the inside of the domes plywood panels, directly facing the sun, showed they were at about 100F. Most of the rest of the panels were at about the dome's internal, air temperature. The temperature of both vertical rows of panels was rather even from top to bottom.
There is room for hope here. In that shading need not cover very much of the dome's exterior to have quite a large effect. The panels covered by the open shutters remained relatively, much cooler. No real heat is being transmitted through the shading shutters. Only a vertical row , of panels, on either side of the open shutters is warmed.
So [in theory if not in practice] simply extending the shutters by about 2' will shield the only panels needing such treatment. [i.e. Shade] The dome is, of course, always "facing" the sun for maximum [effective] slit width during observation and imaging sessions. Or, more pedantically, the shutters and slit are always aimed towards the sun.With regular cranking on the friction wheel to move the dome to follow the sun.
Physically extending the shutters with solid material is now proven to work against panel heat gain. The downside is the ease with which a breeze could catch these large extensions if made of solid material. Louvres might have almost as much wind drag since each blade, of m any, would each act as a wing. Though the actual angles of the blades would vary considerably to be effective in producing shade. The answer is to have more blades and make them both narrower and much closer together.
I am basing these thermal assumptions on early spring sunshine. Even hours of full sun obviously has less heating effect at this time of year. Though the thermal differential of the panels relative to the dome's interior should be higher with cooler air. In summer the solar gain is increased but air temperature is also higher. Yet to be proved. With my new emphasis on solar observation and imaging I need to control hat gain. Which would tend to case turbulent images due to warm air rising through the slit.
Other options include painting only the panels on either side of the open shutters white. Hanging a shade curtain or reflective foil. Netting? Possibly in layers? The ability to breathe, shade and avoid high wind drag is all in netting's favour. A new set of drawer slides could extend outwards to cover only the necessary panels. While leaving the netting supports lying on top of the shutters when not in use. Too clumsy and bulky.
A triangular "sail" of netting might work. It could be tensioned back at the furthest, lower corner from the shutters. If attached to the shutters then there would be plenty of space behind it for air movement. Laying a shade net flat on the panels would be pretty hopeless. I have some green, greenhouse shade net. Which wood pass almost unnoticed on the dome.
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