Temperature Sensor for Primary Mirror

[astronut (John)]

I am about to install a temperature sensor on my 12" mirror.
Where would be the best place to mount it?

Thanks, John.

[wasyoungonce (Brendan)]

Not really knowing what is the best place...my guess would be to experiment. Try 2 sensors, one near edge, one near centre (rear of mirror of course), both at the same time.

Measure the delta (difference) between them...that way you can make an appropriate decision?

Anyway...FWIW that's what I'd do..

[Calibos (Keith)]

I'm interested in the answer to this question too.

My Dewbuster Dew Controller was already the hub for most of the gear installed on my Dob. (3v GLP power output, 4x 12v power outputs, 6x Dewstrip Outputs and a Temp Sensor controlled output for Secondary Mirror Dewheater)

Well, I realised that the Secondary heater was never needed presumably because my Dew/Lightshield on my UTA and cooling fans moving air up the tube keep dew off the secondary all by themselves. Around the same time as I realised this I was also trying to figure out where to fit a PC fan controller to drive my Cooling and boundary layer fans. I put 2 and 2 together in my head and I think I got 5

The dewbuster uses PWM (Pulse Width Modulation) to vary the temperature for the dewstrips. This is often the method used by fan controllers to slow down computer fans. I realised I can wire my fans to the Temp sensor controlled Secondary heater output on the Dewbuster and by swapping the wires in the temp sensor connector and affixing the temp sensors to my Primary and LOTA I can have a fully automated cooling/boundary layer system on the scope. ie. When the primary is warmer than ambient the Dewbuster will power the fans full speed. As the primart temperature approaches ambient it will slow the fans down and when the primary achieves ambient the Dewbuster will power off the fans altogether.

In Irelands climate I generally won't have to worry about tracking a falling temperature all night which can be a problem in other parts of the world where the mirror can never catch up with ambient and get to that magic 2-3ºC delta...even with fans. I''ll be able to catch up with ambient and maintain parity easily here. I also know that there isn't really a problem leaving the fans on all night anyway as long as they are vibration damped. However, fans can gobble up electricity voraciously, I have a lot of Dew,12v and motor gear on the scope but only able to mount a 20AH battery onboard and I have this terrible habit of forgetting to manually turn off the fans even when I'd be pretty sure the scope was already at ambient.

Using a primary and OTA mounted temp sensor to monitor the temperature and power up/down the fans automatically would be a boon for me and my 20AH battery

[badabing82]

I'm also in the process of looking into this as here in perth the temp drop can be quite severe in the summer months with close to 20 degree drop in some cases..... in any event what data logger and temp probes is everyone using? at reasonable cost?

[Moon (James)]

in any event what data logger and temp probes is everyone using? at reasonable cost?

I'm going to give it a try with:
Logger : ThermoHD
Probe : Temper1 (also check eBay)
Thermal Paste : Stars
James