Cooling Fans for Cat's and Mak's

[John]

I'm thinking of getting a cooling fan for my C8 cat to speed up cool down.

The one I'm looking at fits into the visual back and draws air out of the OTA, presumably shortening the time that it takes for the scope to reach temperature equilibrium (about 1 hour at the moment).

These things claim to cut the cool down time in half. Does anyone have exeperience of using something like this ? - is it likely to work ?.

While I can see that it would help reduce the temperature of the air inside the OTA more quickly I can't see how it could do much to cool the optical glass elements - but maybe thats less important ?.

John

[Kaptain Klevtsov]

Hi John. Saw something similar for the OMC140 when I had that and I was intrigued to discover where the cold air gets into the 'scope. From what I could see the fan fits in the EP hole and sucks, but I have no idea where the air gets in through.

From a heat transfer point of view, any air movement inside the 'scope would be good and replacing the warm air with cold air from outside would be better. The air movement would have a dramatic effect on the cooldown time of the primary mirror as it usually sits in a stagnant pool of warm air.

Have you tried having the 'scope pointed down with no EP fitted? I read somewhere that this lets the warm air float up out of the 'scope helping it to cool more quickly.

Captain Chaos

[John]

Have you tried having the 'scope pointed down with no EP fitted? I read somewhere that this lets the warm air float up out of the 'scope helping it to cool more quickly.

Captain Chaos

Thanks for that suggestion CC - I'll give it a try. Up to now I've been letting the scope sit horizontally as it cools but I can see the logic in your suggestion - after all hot air rises !.

The other thing I am concerned about in using a fan is getting dust into the OTA - as you say the air must come in from somewhere.

John

[tom.yates]

Im with cc , I always point the scope lens to the ground and the focuser end up with no diag let the air rise up out of the tube.

[SteelRat]

Heheheh, it's amazin the stuff you can pick up here due to the common sense of others. Good job I'm used to being a dullard