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Old 14-02-2014, 07:14 AM
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SkyViking (Rolf)
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Location: Waitakere Ranges, New Zealand
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Quote:
Originally Posted by Rac View Post
Looks good. I've been thinking along the same lines for my scope. In my case i should be able to just use the brass spider vanes and just insulate them at the middle. Although i could the your fan idea with mine first.

Are you going to do something similar for the primary.

Raymond here from Whangarei btw.
Thanks Raymond, yes when you have thicker vanes it should be no problem to use them directly. Although you could also just glue thin copper strips to them. It probably doesn't make a difference if the vanes are already relatively thick.
Using a fan first is worth a try though, it might be enough, all depends on the local conditions and your particular scope (mirror size etc.)

I'll see how it goes with the primary this winter, that's when the optical surfaces are most prone to condensation.
Another reason to perhaps make a primary heater would be to be able to turn it on after an imaging session so that the primary doesn't gather dew in the early morning. I believe in winter this happens regularly after the cold mirror is covered up and I close up the obs. It's not good for the coating, so keeping the mirror just above ambient for the rest of the night would be a solution. Then I'd just turn the heater off the next day when everything is warm again.
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