I built a removable insulating cover for my MK-66. That way I can cool it down faster without the cover and put it on just before observing.
However, I still have the feeling that I have some turbulence left in most cases . When I manage to properly cool it, it performs very well .
The whole purpose of insulating an OTA is to NOT let it cool, or rather to slow the rate of cooling. Insulation by definition cannot cannot accelerate or assist cooling, only slow it down.
Think about what is happening with a bare OTA - the tube cools down much faster than the primary mirror and baffle tube, so a heat differential is created between the cool tube and the warm internal components, and so a heat plume is generated inside the OTA as the heat is transferred through the air inside the OTA. Now if the OTA is insulated, the tube will not cool faster than the primary mirror and baffle tube so a heat differential is not created and hence there will be no heat plume generated.
The entire purpose of this is not to prevent the cooling of the OTA, just to slow it right down. You can still wait for the OTA to cool, but depending on the size and type of scope you have, your location and the starting temp of the OTA this can take anywhere between one to four hours. But by insulating the OTA, there is no waiting cool down period so you can rip the maximum magnification that seeing conditions will allow from the very start.
The trick with insulating the OTA is not to make the wrap too light or thin as this will not provide the necessary insulation properties required. Better to have thicker/more effective insulation as this improves the slowing of the cool-down rate. But this also does not mean that the insulation that is required needs to be an expensive material. I've made a stupendously effective wrap out of a re-purposed yoga mat that I rescued from the tip! The best part of this mod as an ATM project is for you to explore the materials you readily have at hand, and the upshot of this could be that you spend either nothing or very little on the wrap, or a nominal amount to buy new materials.
PLEASE NOTE that this insulating trick/mod is ONLY for closed tube OTA's such as SCT's and Maks, not for open tube OTA's. Refractors could benefit as well, but not by the same margin because their internal components are totally different.
Edited by maroubra_boy, 18 April 2021 - 07:27 AM.