Skywatcher 250px cooling fan

[Paulb3098]

Hi, looking to fit a cooling fan on my 250px. Can anyone recommend a model / brand / make ?

Thanks

Paul

[brantuk]

I'm in the middle of fitting one to my 16" dob Paul. After a bit of research I decided on the Noctua brand and I got this model: NF-S12A ULN (ultra low noise). For a smaller dob you would want a slightly different size and rating, but they have plenty in the range to choose from.

Below I've included a very interesting link about the theory of dob fans and the website I used that gave me good service and quick turn around.

http://www.quietpc.com/noctuafans

http://www.fpi-protostar.com/bgreer/fanselect.htm

Hope that helps

[sbooder]

The predrilled holes on the back of the mirror cell fit an old PC tower chassis fan a treat.

[Paulb3098]

Thanks guys, really interesting article, especially about the baffle.

Paul

[sbooder]

This is my old Baffle, I have not taken a pic of the new one yet but they are both made from foam bedding mat a lot lighter than the plastic ones.  I covered mine in flocking, not really needed but I go flocking mad, anyone here will tell you.

[TractionMan]

I'm in the middle of fitting one to my 16" dob Paul. After a bit of research I decided on the Noctua brand and I got this model: NF-S12A ULN (ultra low noise). For a smaller dob you would want a slightly different size and rating, but they have plenty in the range to choose from.

Below I've included a very interesting link about the theory of dob fans and the website I used that gave me good service and quick turn around.

http://www.quietpc.com/noctuafans

http://www.fpi-protostar.com/bgreer/fanselect.htm

Hope that helps

Great links! I'm likely to add a fan to my dob as well. Might add that the Noctua fans are very nice indeed. Got a few of them in my latest PC build and I'm more than happy with them.

[AlexB67]

Interesting read. The argument for fitting one seems quite compelling, even on a 10 inch pyrex more that I ever thought. Reading a bit further found some interesting reads that I now lost in my history, but suggested a heatsink is  not a bad idea, and another blog posting that even the one fan rear config can't keep up very well.  I saw some pretty hefty configurations with multiple fans mounted on the side as well, rear and a heat sink, only with that was the mirror able to keep up, don't think the aperture was that large either. Still a simple rear mounted fan would presumably go a long way towards an noticeable improvement and would be easy to do.

Seeing I got boxes of fans kicking around and even some heatsinks it could be some interesting DYI to think about.

[michaeldurban]

whilst we are all showing our stuf...

[michaeldurban]

Mind you...I installed the mod (as shown above) and it worked perfectly.

I did find that when you cool down the scope it is better to turn the fan off after

an hour or so..

At first I left the fan on whilst stargazing and found that my mirrors started to dew up.

I thought this was because the fan didn't work properly.

But what actually happened was that cool moist air was sucked away from the grass, dewing

up my mirrors.

So now I switch it off after a while, and I don't have that problem anylonger.

[sbooder]

Mind you...I installed the mod (as shown above) and it worked perfectly.

I did find that when you cool down the scope it is better to turn the fan off after

an hour or so..

At first I left the fan on whilst stargazing and found that my mirrors started to dew up.

I thought this was because the fan didn't work properly.

But what actually happened was that cool moist air was sucked away from the grass, dewing

up my mirrors.

So now I switch it off after a while, and I don't have that problem anylonger.

I find that sometimes just for a few minutes that turning on the fan while viewing can get rid of tube currents then turn off again.

[knobby]

Mind you...I installed the mod (as shown above) and it worked perfectly.

I did find that when you cool down the scope it is better to turn the fan off after

an hour or so..

At first I left the fan on whilst stargazing and found that my mirrors started to dew up.

I thought this was because the fan didn't work properly.

But what actually happened was that cool moist air was sucked away from the grass, dewing

up my mirrors.

So now I switch it off after a while, and I don't have that problem anylonger.

Are you sucking or blowing ?

I might try sucking, so as to pull the heat away from the mirror rather than blowing cold air towards it ?