Focus Modual Question

General
1

I am using an Optec Direct Sync ACF focuser with a FocusLynx controller. It seems when using the temperature compensation feature the focuser is trying to follow the temperture drop using the hundreds of degree change instead of tenths. I have confirmed with Optec that their temp probe isn’t that sensitive, and the FocusLynx controller algorythm is also using only tenths of a degree. The focuser does change a small number of steps with hundreds of degree change, but after about 40 minutes the focus isn’t as crisp anymore. I have to run a auto-focus routine, then it seem to track ok again for a while. I believe I have the temperature compensation value set correct, I used the data from two nights of doing the auto-focus about every 10 minutes. Since Optec says both the temp probe and the controller is using only tenths of a degree moving in hundreds has to be coming from SGP. I believe the focuser trying to follow such small temperature changes when it’s not that accurate is inducing errors into the routine. Is there a way to have SGP track the temp change and move the focuser only following tenths of a degree not hundreds?

Thanks
John

2

I fully agree with you: we don’t want that the noise in the temperature signal causes permanent corrections of the focus position, IN and OUT. Each reversal in direction will even cause the backlash compensation to operate. Thus unnecessary corrections of the focus position are causing a lot of traffic. This situation is unfavorable.

I made a related feature request in november 2017: Focuser Temperature Compensation - Focus Position threshold - Feature Requests - Main Sequence Software

Unfortunately, at that time there was no discussion based on facts. I hope that this subject will be revisited.

I think a focus position threshold is even better than setting the number of the significant decimal places of the temperature value. If we are allowed to set a focus position threshold we could account for the Critical Focus Deviation (CFD) of the optical system that is used - this is the relevant quantity for the decision whether a focuser temperature compensation has to be applied or not.

Bernd