Fan mount on 300P

[mitchelln]

I've just noticed that the mirror support on my 300P has mounting holes for a fan. Is this a worthwhile mod?

I assume that the fan should draw air from the mirror side exhaust it backwards and not blow over it to reduce it throwing dust over the mirror?

Is it still a good idea to have some sort of filtering?

Thanks!

[umadog]

Yes! You will drastically reduce (i.e. roughly cut in half) the cooling time even with a slowly revolving fan: http://www.fpi-protostar.com/bgreer/fanselect.htm

Your tube is open-backed, so the most efficient way to cool the mirror is to have the fan blowing air at the mirror (blowing up the tube, towards the mirror). You don't need a filter and don't have to worry about dust on the optical surface. Not a problem. One reason I say this is because once I saw a guy who'd bought an insanely powerful fan (clearly he hadn't seen the graph in the above link) that had obviously been sucking up nearby flying insects judging by splatter marks on the back of the mirror. All the splatter marks were located in the area surrounding the fan. In general, I don't think anyone reports dust problems when using a fan.

[mitchelln]

Great! Thanks for your reply