Quote:
Originally Posted by Stefan Buda
Yes, I would definitely expect the same problem when the ambient temperature is dropping. However not blowing away the boundary layer may result in poorer images. A planetary scope needs to be designed very carefully regarding thermal issues.
|
That's very interesting. I would never have thought that cooling fans would cause astigmatism by blowing air locally on a glass surface. I guess it makes sense, the bigger the volume of glass the more amplitude in change.
So the challenge is to mount a large chunk of glass so it keeps its position mechanically but still has room to expand and breathe. How do you do that? Cement it with a compound that has the same or very close properties as the glass you're using. Like a crumple zone?