Auto focus not working

Last night my first two subs auto focused perfectly fine, as im shooting 20 min subs i focus afeter each one to deal with any thermal shift (a problem with the fsq106), these were fine, then every attempt to get focus after for several hours ran through the procedure founf the focus then the subsequent sub was out of focus, eventually after several hours the v curve totally disappeared and all i was getting was a flatish line. Any thought on why it would work fine then completly fail progressivly worse and worse?

Sometimes this happens with excessive backlash or by virtue of some mechanical anomaly that does not actually allow the focuser to return the calculated focus position. But if it worked fine at first, the most likely culprit is gravity.

Do you have backlash compensation enabled? If so, make sure it’s larger than necessary so it’s good to overshoot.

Also, did you look at the sky and check for clouds when you saw focusing issue?


l use a backlash of 30 set to ‘in’ with my 106. My graphs went a bit funny at one stage - I was getting slippage, so it’s worth double checking all the grubs holding the motor to your focuser are tight (and that they’re located squarely on any flat surfaces). My v curves have been spot on since I took those steps.


Backlash on my 106 is basically zero but that is after I replaced the entire focuser with a Starlight.
Takahashi optics are super but their focusers are pretty crappy. I had this sort of issues a few years back
before I dumped the Tak focuser and equally crappy Robofocus.

thanks for the tips, i have made sure all bolts etc are tight and there is no movement in the system, a focuser upgrade as desirable as it is, is not on the cards and would have to have inbuilt motorised rotation to be consideed.

Do you have an especially small chip and FOV? I have used the 106 for many years and have found a rotater to be seldom needed.

well i spent some time looking in greater detail at the focuser in action and it was slipping on inward travel, i have tweaked and tinkered and its now equal again, something must of got loose somehow, it was not apparent.

i really would like to be able to frame better even with my 8300 chip it would be of advantage, but needs to be remote.