20.05.3030 Pt.2: Themal issues and poor seing conditions.

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11.47. 64/59F As the cloud is denying me the ability to capture anything worthwhile, for most of the time,  I am playing with white screens for the plywood, dome shutters. They were showing 44C on  my remote thermal 'gun.'

So I have stapled a large white, agricultural storage bag [providing two layers of non-woven cloth] to the lower half of each shutter. I have also opened the ground floor doors fully and the doors to the veranda for maximum ventilation.

I wish I could see some obvious reduction in the thermal agitation clearly visible on the monitor. The sun keeps going completely out of focus into a soft mist of white haze. [See the B&W image right.]

I have changed from the Lunt B1200 BF to the PST BF to shorten the exposure and avoid using Gain [0] 1.85ms for 320fps.

As I am not capturing, but the camera is still recording and exposed to at least some of the sun's [filtered] heat, I have turned the dome slit to the east. This will provide shade for the telescope objective.

The ZWO ASI74MM camera is showing 39C even when not actively capturing video. It dropped back to 36C. A small cooling fan for the camera  would not be difficult to arrange. Not to achieve low temperatures but just to remove excess heat.


I have my shed's pitched shed roof  right alongside the observatory to the east. Presently showing 32C on the western, non-direct sun pitch. Whoops! 50C on the side facing the sun! It is no wonder the seeing condition go rapidly downhill as soon as the sun reaches the shed roof! It is not until the sun reaches the meridian, due south, that  the sun is  no longer over the shed roof from the telescope's viewpoint. Wind direction will decide whether the heat s still brought into the field of view.

There is tall, prickly hedge on the far side of the shed. Which I have been trimming each year. Perhaps I shouldn't? It could easily be allowed to grow upwards to provide cooling shade for the shed roof. This is the most critical direction. Because the morning is [supposedly] the time for best seeing. Before the sun has a chance to heat the ground and nearby buildings.

The shed roof could well be the explanation for my rapid loss of good seeing in the mornings. The roof is covered in dark red, corrugated, fiber-reinforced, asphalt sheets, called Onduline. It certainly gets hot! There is no obvious lightweight alternative for roofing except white painted, corrugated steel sheeting.

Further measurement showed 50C on the bare plywood panels of my observatory walls. I'd have to take a wide brush and white paint to everything to reduce local heating of the air around the telescope.

I spent the cloudy afternoon cutting back 20' willows. They were blocking the sun yesterday evening as the seeing conditions settled slightly. Being nearer to the observatory than the background trees they had to go. Most were only an inch or so in diameter at half way up their skinny trunks.

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