|
I don't know much about the feathertouch focuser but I can tell you a thermistor sensor is a 2-wire ~10kohm resistor that varies logarithmically with temperature and will not have any polarity.
Sensor position would probably be based on which part of the optical chain has the most bearing on changes in focal length due to changes in temperature. If it's a lens or a mirror or an eyepiece that would probably heat/cool slower than the ambient temperature so you'd want to position the sensor hard up against a solid part in the vicinity so it also heats/cools at a similar rate. If the issue is the air itself inside the tube, that will heat/cool a lot faster, then you'd want the sensor to be lightly mounted against the tube itself.
Hope these comments are of some assistance, but hopefully someone familiar with the gear can give a better answer.
|