Quote:
Originally Posted by g__day
I have only seen this happen once before (and there is a thread about this on the ZWO forums - the attempted resolution seems to be update the firmware.
The issue is when the temperature is between 23 - 26 Ceclius (like right now) the ZWO focuser (EAF) temperature probe can shift like a pendulum over a 1 - 2 minute cycle reading between 16.2 and 22.4 degrees.
I see the temperature readings fall to 16.2C - at around 0.1C every 1-2 seconds - then when they hit 16.2C they rise at the same rate until they get to 23C - then they fall and the process continues over and over and over!
My software has a trigger saying if temperature varies by 0.5 C trip and autofocus and otherwise adjust focus every 0.1 C automatically by 4 steps.
So I noticed too many autofoucsers then I looked at the temperature on my focusers. The Moonlight focuser on the scope clled by SGP is reporting a rock steady 24 degrees - the ZWO controlled by APT is seeing the ZWO change temperature by 0.1 degrees every 1-2 seconds!
So I turned both temperature compensation and refocus on 0.5 degree temperature changes off in APT.
Have other folks witnessed this and did the firmware update 1) succeed and 2) solve the problem.
The ZWO thread has a user measure the 100K resistor they use and point out the exact problem there - dating back over a year!
Many thanks,
Matthew
PS
Switching to Autofocus on filter change - where I am running Luminance 3 x 5mins, Red 3 x 5 mins, Green 3 x 5 mins and Blue 3 x 5 mins - so rather than autofocus (which takes 2-3 mins) every 30 minutes - I am trialling doing it every 15 mins now to see what that does to my image quality - using ASTAP to compare!
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Hi Matthew,
I'd say it's more likely a Hardware issue than software. Are you using an external temperature sensor that plugs in to the focuser or are you relying on the sensor built in to the ZWO EAF? If it's the internal sensor it may be confounded by heat generated by the motor and electronics within the EAF and if that varies with time so will the temperature.
If you are using the external probe I'd check the wiring and connections for any poor or intermittent contact by lightly wiggling the connector end and then the sensor end of the cable and along the cable itself. You can even use a feather or something similar to lightly move the cable without transferring any heat from your fingers etc. If there is a significant change whilst wiggling then you may have faulty contacts or wiring. You may even have poor/loose thermal bonding between the thermistor and its case.
If you are using an external temperature sensor it may be possible to test it further with electronic test gear to rule in or out a sensor issue as I believe the external sensor uses a 100 kOhm NTC thermistor.
Best
JA