Experiencing challenges with maintaining sharp focus when using Voyager’s autofocus routine during significant temperature drops. It seems that the autofocus needs more frequent adjustments than expected; particularly in the early hours.
Has anyone else faced this? Are there any configuration tips ; strategies to improve focus consistency as temperatures shift overnight? I have checked SCT autofocus HFD Parameters determinationsfmc documentation guide but the issue remains unresolved .
Additionally; I am excited if there are specific settings that can make the autofocus more responsive to subtle temperature variations.
By what you have posted, I assume you are using an SCT? I used to image with a C925 and to be honest they are challenging to keep in focus with temperature changes. They tend to have a lot of focus shift with changes in temp, and you can not successfully just use temperature change as a focus trigger as the focus run will be triggered by the temperature change at the end of the current exposure, but the tube will likely take time to cool down (Or warm up) and the focus will keep shifting for some time.
I found the best way with mine was time triggered focus runs and lots of them, trading a handful of exposures each night lost to focus runs, for the subs that were shot all being in better and more consistent focus.
SCT are not really well suited for AP. With this telescope you must have at least a couple of hour of thermal stabilization before you use. If for example you have an observatory and you open and start doing sequence without waiting for thermal stabilization the focus is unpredictable and this is not a question of Voyager’s autofocus.
Is not unresolved just doing the first light wizard at thermal stability.
We use 4 C14’s here and have quite a bit of experience with this. Is this an Orange Tube or a newer variant or different brand? The orange Celestron’s are challenging, but the key is to improve your workflow. Our 24in PW CDK has less of an issue with temp/focus changes, but we still had to find the right mix of when and where to inject focus requests.
For SCT’s I usually tell students to open up at least an hour before obs. and point the scope at Zenith. If you’re doing skyflats, this takes care of this. Focus first, even if your target isn’t up. Focus at start of series. If it is a big series, focus every 1-2hrs. If you focus in Clear every time, it shouldn’t eat up much time in Voyager. One gotcha with SCTs is with wide temp changes (we’re in New England), I do have to manually change focus because our electronic focuser can’t travel far enough for the whole year. That triggers a collimation check, sometimes a model update. The EdgeHD’s are not as prone to this issue, but still worse than a refractor. We do not use temp compensated focus.