PDA

View Full Version here: : Feathertouch thermister question


graham.hobart
28-05-2013, 07:36 PM
G'day fols. My temp probe came today for my Feathertouch focuser along with a temp probe, and a grey and a black cable- grey long black short. It didn't come with any instructions on how to set it up and the software has a guide on calibrating it but not how to connect it.
Anyone can help me sort the cables out? I have the focus boss set up with the hand box and the little junction box thingy.
Also how are folks attaching the thermister?
Graz

StutzJr
01-06-2013, 12:50 AM
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.