cooling down time

[Daniel-K]

i know my reflector needs about 40 minuites to cool down but what about my 66 semi apo?

[Moonshane]

I work on about 5 minutes per inch of aperture so perhaps 15-20 mins? in honesty though unless imaging, I suspect you could observe as quickly as you can set up with that sort of scope, especially at lower powers for which it is presumably designed?

[umadog]

Your apo needs very little cool-down time. Tube currents are generally less of an issue with a refractor. There are various reasons for this. For instance, the refractor is a sealed tube, the glass is at the top, the light only has to go down the tube once, etc.