Simple Autofocus Feature

I wonder if the following feature could be considered? If there is already a way of doing this, please accept my apologies for bothering you. (And please let me know how!)

Following a night’s imaging, my focuser has usually racked a fair way inwards from the position it started in at the beginning of the session. When I start imaging the following night, it is usually too far inwards (from the previous nights imaging) to get a decent focus run straight off. So, at the start of every session, I have got into the habit of backing the focuser out by a couple of hundred points using a Coarse Focus control setting. This is repetitive, and occasionally I forget to do it.

I wondered if it might be possible to build in an end-of-sequence step that backs the focuser out by a user-adjustable number of steps. Of course, I appreciate that this might not be a ‘bullet-proof’ solution since a sequence might abort early in the evening before temperatures have fully dropped. Nevertheless, there is usually no real harm in being a bit too far out at the start of an autofocus run (I’d certainly rather be a bit too far out than in). And in any event, so long as the ‘feature’ was fully user adjustable, people could choose to use it or not. Maybe we could have a ‘Return to Sequence Start Point’ feature rather than a ‘fixed amount’ feature.

What do you think?

I would think a “restore to starting position” would do what you want without needing a custom number of steps.


I agree. That would probably be the best solution.

I keep an Excel spread sheet on my desktop on which I record and plot the focuser step and the temperature periodically when I’m imaging. When I get ready to start a sequence, I look at the temperature, refer to my spreadsheet, and use “GoTo” to set my initial position. Works great.


Yeah, I’m not sure why for temperature enabled focusers there’s not an option to do a temperature based start point. That would be an obvious fix. Don’t recall if that was one of the requests on the focus improvement thread.



I made a similar request with this thread:


I think doing this based on the temperature compensation curve makes sense, assuming your focuser can reliably move to an absolute position. Moving to the same position as you started at last night would only work some of the time if you’re in a place like NC, where it can be 65 at the start of one night and 45 the next, at least at this time of year.

Perhaps, but I just wanted something simple. I image ~200 nights a year and find that I generally can back out by a set amount to get a decent starting position. (I have this set up as my ‘coarse’ adjustment.
I wondered if we were more likely to get the feature if I asked for something that wasn’t complicated.

I am late to the party here - and maybe I have misunderstood. You know that you can start at a fixed focuser position every night? I do it that way and I am never too far off focus. In fact, I have it set a little to the right (looking at the graph) of the expected focus position - that way I never have any problem when it runs the auto focus at the start of the sequence. My chosen focus position is OK (even though off exact position) for the plate solve to work OK.


Not at all Kinch. And thank you. In my original post, I did wonder if you could do what you say. How do I set up SGP so that I have a defined starting position?

In the filter set up - you will (should) have entered the focus position that you want to start with (and the offsets if you need them for other filters). In this case position 1030 for Lum.


In the focuser properties, select " Set absolute focus position for first filter use"

In this case, when my sequence starts up and it does an auto focus prior to running the sequence - it takes the focuser to “1030” ….and then starts the auto focus run.
The “1030” (or whatever you have) just needs to be in the ball park so that a plate solve can also work to bring the scope to 1st location.

Hope that works for you.


I would also love to see a rough position table implemented based on temp, typically I start at position 9000 to end on 8800 or so which is to much to recover from the next night, so if you start the system backup I need to remember to move the focuser into whatever the Temp is range …

@Jared, @Ken, Any update on this request to have the focuser moved to a more-or-less correct position based on temperature at the beginning of a session? I also have a spreadsheet of about 20 temperatures with their focus positions, and manually move the focuser at the start of every night, but sometimes forget or it’s a temperature I don’t have and autofocus either takes a really long time, or sometimes doesn’t work.
Would be really nice for SGP to automate this.

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