Fan speed control

[Photon]

In the posts for Dew control it has been recommended to run the mirror cooling fan to prevent dew build-up on the secondary mirror.
There are Fan Speed controllers for computer fans that could be adapted for scope use, some controlling up to 4 individual fans and some with remote control. The following link shows some of the devices available and coupled with a bit of Astronomers ingenuity might be a useful device.
http://www.directron.com/speedcontrol.html
If anyone has had any experiece with similar devices maybe they could let us know?
Ian gillespie

[davidpretorius]

thanks for the link Ian, I must admit since having the peltier / fan system, the eyepieces may still be fogging up, but neither mirror has this winter so far.

[Photon]

Hi David, Yes it seems like a good way to go and less complicated than having heaters everywhere. I started looking for a speed controller to just keep the fan ticking over with a column of air moving through the OTA and little vibration. The speed can be adjusted to just keep the dew from forming rather than have the fan running full pelt. A ready built computer fan controller may be an easy way to go.
Regards IanG

[davidpretorius]

I hardly notice any major viewing issues at full blast on the fans, it is only at high mag imaging, it becomes an issue