Hi all
I was out tonight with the new baby - a C8 XLT for its first light (with me anyway), and noticed that it really took ages to come down to temp. Not as long as the 12", but a while nonetheless. It's still around 10 deg C outside at 9:30pm so it's not even cold yet. It'd brought it outside from the lounge room - where the heater was going to keep the house warm - at around 20 deg C. My guess is that the mirror temp was about the same at that point.
Without a well-placed temperature probe inside the SCT's mirror cell, it is going to be hard to set up a way to gauge ambient/mirror temperature differential, but I'm thinking of a new idea. Given that winter temps are likey to be around the -5 deg C mark (or colder) where we (Macarthur) view from, why couldn't I use my 12v compressor-driven Engel car fridge to pre-cool the
whole unit to a measured -5 deg C (or whatever the forecast minimum was going to be) and keep it there until the outside temp was down to the same? I could then bring it out and we'd be at or about ambient. Driving to a viewing site I could keep the SCT in the fridge until I got there and then not have to wait until it cooled off naturally.
I know it initially sounds silly, but being nice and small I can mount the whole SCT, in the fridge, in an upright position - i.e. the corrector plate facing up. I can even manufacture a bracket to hold the scope in position by its dovetail so the fridge effectively becomes its carry box.
My question is this: what if I miscalculated the forecast temp at set up time and the mirror temp was
below the ambient outside air temperature by a measurable margin when I set up? I can set the fridge/freezer to cool to at least -40 degrees below ambient, so there is a lot of scope in the temp range I can set. The seals are very good and condensation is nearly totally absent. It's a very dry cold.
Does anyone have any ideas on this?
Cheers
Chris