That part is not the real problem. It's more understanding C++ and the layout of the code. KStars/EKOS is a complex beast and not the best starting point to learn I'm afraid

(Just wanted to have a look at what is needed to add also the Hour Angle to the "Mount & Alignment" overview, instead of issuing a wish. But even that looked to me like Olympus Mons to an ant )

Unless your belt is tight... I don't see how there wouldn't be backlash. I have mine loose enough to get off so I can do large adjustment. I just put a 'bar' on one side of the belt to take out some slack, but slide the bar out and I have slack enough to get it off the gears.

Most focuser motors have a gearbox, this is where the backlash comes in. It’s not typically from the belt.

Well, that is probably true for the pro units, but if you have a 3D printer, and too much time on your hands?

Off topic: That's a cool idea for design. I can't do it on mine, but I'm assuming that's a rotator as well?

On Topic: I also use a 3D printed focuser, and I have similar issues with backlash, though usually it's pretty good about it. I'll put it on my list of things to look at doing. But I've been quite involved with a local makerspace lately, and that doesn't show signs of letting up.

I'm also doing the same. Mine is the Deepskydad AF1. So far, it's been working great. The focuser module hasn't worked very well lately, once the module creates the "donut" it gets lost and reverts back to the original position. So I've been using my bahtinov mask. But to the subject of backlash, the bar in the photo below seems to do the job. I'd like to have some sort of pulley setup with a spring, but this works.

I'd happily volunteer to code a unidirectional focuser, if I get one or volunteer testers!
If you're interested, respond on this thread or message me.
I've been thinking the same thing for a while.
I warn you, though, that I believe backlash is only part of the problem.
I believe the HFR calculations (and, of course, seeing) are noisy and contribute to the lack of good v-curves.
Hy

above should have said:
**one or more volunteer testers**

Definitely willing and going to test whatever you come up with
As for the HFR calculation, ISTR that one of the last commits had improved that and its stability/reliability.
(Also nice might be a separate tool to measure backlash, though it would already get much easier with an unidirectional focus method by just reversing the direction)

count me in!
currently traveling, but starting Tuesday my thing should be up and running again...

Michael

Sorry I've never gotten back to you on this--been working on something different.
That said, I have gotten a crude linear focus algorithm working on my development raspberry pi.

However, the reason I'm writing, is I've found that the mainstream focus is working a lot better for me now, and I wonder if that's true for you others.
I've switched to using the full-field focus (there was a bug in that scheme, but Jasem fixed that month or so ago), with Annulus of 20% & 75% -- so it uses a "donut" area,
not the inner 20% (to avoid a galaxy or nebula I might be pointing at) and not the outer 25%. I've been using about 10s exposures with moderate gain (75 on the ASI1600).
I don't think there's anything magic about these numbers, and it might be fine without the annulus.

In any event, it's been OK for me, are you folks still having issues?

Yes, I had also noticed that. The curves IMHO look smoother, so somehow there had been some additional noise that is gone now.
Haven't tried the field modus lately as I was looking at field curvature issues, and wanted to make sure the focus is set at some 2/3 distance to the border. Though that should in principle also be possible with filed modus and a narrow donut around 66%.

So no urgent issues anymore. But if you have the linear mode in place already - maybe that could easily be extended to a backlash measurement? (Assuming with 'linear' you mean just scanning through one direction).