[Wavytone]

Hi Lewis...

There really is a reason why telescopes and observatory domes should be white.

A bare aluminium OTA is about the worst choice possible as it’s an excellent thermal conductor. I guess you also aren’t aware that cooling a mak is also not the best thing to do to stop the internal tube current. It has been pretty well established that insulating the OTA of maks (and SCTs) will both stop the internal tube current and prevent the OTA from cooling rapidly - this helps significantly with keeping the corrector dew free.

If I were you I’d have it powder coated in pearl white, there are places that will do it for a reasonable cost. Or have some sort of close-fitting insulating sleeve that fits over it.

Secondly pearl white will stop the scope getting hot if it’s in the sun, and minimises the radiative cooling to the sky at night.

I know some will dispute this however some years ago I had the chance to test about 100 cars and some samples of sheet metals with an optical pyrometer to find out how they perform in the real world in order to assess the range of temperatures that would occur in trains stabled in maintenance centres, and power required for air-conditioning night and day winter or summer.

Pearl white was consistently the best followed by the lacquer whites.