FMx + Optec TCF - strange temperature reported at end of focus run

[Paul Luckas]

We're experiencing an intermittent temperature controlled autofocus idiosyncrasy where the final reported temperature is -274.0

11:42:38 19:42:38 ** Beginning Focus Run **
..
11:42:40 19:42:40 ...Current position: 3758
11:42:40 19:42:40 ...Current temperature: 13.9
..
11:46:38 19:46:38 Focus position = 3761 Avg HFD = 2.44 Avg FWHM = 1.72
11:46:38 19:46:38 Temperature: -274.0 Filter: Clear (slot 1)
11:46:38 19:46:38 ** AutoFocus Completed **

The initial reported temperature is correct, but by the time we're at the end of a 2-4 minute focus run (using FMx via ACPS) something has gone amiss. I thought the problem might be hardware related, eg a faulty temperature probe or use of 50 foot TCF control cable, but at this stage I've only seen the problem occur during a focus run.

We're using FMx's Acquire Star feature, running periodically from ACPS. Latest versions of all software.

Has anyone seen this and have any clues?

Paul

[Dick Berg]

Hi Paul,

I had a similar issue with temperature reported from my focuser (a TCF-S). I don't remember the value reported, but when the ambient temperature sensor attached to the focuser went bad, it reported a screwy number that was clearly not the real temperature. I bought a new probe from Optec, but it turned out that it was only the connection to the focuser that had become loose enough to cause the problem. You might check that connection.

Coincidentally I think, -274 is a few tenths of a degree C below absolute zero.