Hi Fabio,

The Kstars Handbook with the 3.6.5 focus changes is now published. The links I sent before now point to the latest version. Here's the link again for the Focus section...

docs.kde.org/trunk5/en/kstars/kstars/tool-ekos.html#ekos-focus

Thank you for letting me know.
In the meantime I am taking my time to get familiar with the autofocus routine using the info you gave me.

Thanks again!

Hi all,
unfortunately my woes with autofocus continue.
I'm now trying to setup offsets and I tried to use the builder tool.
Only, every time I open it it's empty and I don't understand how to select which filters to include.
Any help is appreciated.

Pick one filter you want to calculate offsets for and "lock" the other filters to your pick in the "Filter Settings" popup. Launch the Build Filter Offsets popup (from Filter Settings).

(You shouldn't have to do this - I'm fixing it at the moment. Hopefully will be in the next release).

Thanks for the explanation, eventually I did get it but yeah, it wasn't really obvious and the kstars handbook fails to mention it. No worries.

Something I've noticed is that the focus module keeps forgetting my preferences, in particular the full field vs subframe setting, and my preferred focus starting point (though that varies based on my optical train)

I recently got an Askar V, so I have 6 different combinations of effective focal lengths between 270 and 600mm. At 270mm good focus is achieved with my ZWO EAF at approximately 5300; at 600mm, it's around 25000. Haven't yet had a chance to try the other combinations, but it would be nice to specify a focus range limit for a particular optical train: 5000-5600 for the 270mm combination and if focus fails, keep scanning the acceptable range while waiting for the clouds to clear or me to remove the lens cap. When I looked at my telescope a few minutes ago, it had somehow decided to search around 6200 which of course wouldn't work...

And with my particular rig, using full field instead of auto star selection seems to be critical to getting good focus. Every night I have to set that in the focus module, and every evening when I power up my computer that setting has not persisted.
kstars 3.6.6 Beta / commit cec08899d468665e327287296b4e7a4edb5c40d1

Hi Chris,

There was a recent fix for radio buttons put into Focus that I think, should have fixed the full frame vs subframe issue. I don't know how upto date your commit is, but it might be worth pulling the latest. If that doesn't work then can you send me a screenshot of how you set the buttons and how they are set when you restart your system and I'll work out what's going wrong.

Auto Select Star is only relevant to Sub Frame where you are using 1 star for Focus. If you are using Full Field then the system ignores Auto Select Star and always uses all the stars within the selected mask.

The start position is obtained from the focuser. It sounds like you have 1 focuser and many scopes. And what you're asking is that the start position for the focuser is driven by the Optical Train not the focuser device. Is that right?

I can reproduce it with github.com/KDE/kstars/commit/0d95014454c...424f04963241b7e33b48 (Date: Tue Jul 18 01:49:23 2023 +0000)

Here's what I expected, and how I set Ekos before cleanly shutting down Kstars


And this is how it looked after I started Ekos... somehow it goes back to subframe, even though I wanted full field (subject to my configured mask)


As for the focuser, that sounds like a good interpretation of my suggestion. I have 6 combinations of optical elements I can connect to the main body, and I've defined an optical train for each combination. Perhaps it's a niche use case but I'd like to link the focus starting position to the optical train, at least as a hint to autofocus. For now I have those set points in a text file since I rarely (maybe once a month) swap optical elements around and it's not a big deal to just go to the focuser tab and set the focuser absolute position.

Hi Chris,

Thanks for the screenshots. I've pushed a fix for the Full Field / Sub Frame issue.

I've started looking at the focuser position issue, but its more complicated so will take longer.

Yep, that full/sub-frame button fix works. Thanks!

I won't be too sad if somehow linking focuser position to optical train doesn't happen any time soon. It was just a "hm, this would be nice to have..."

Refine curve fit is pretty amazing, and really ought to be enabled by default. Enabling it has dramatically improved focus the last few nights.

Thanks for the feedback Chris. Usually I don’t make new features “default” until they have bedded in. Glad to hear it’s working well for you.

Just looking at your v-curve. Where you get a horizontal line of points on the right (points 1, 2 and 3). That could be un-corrected backlash. If it’s a 1off then fine but if you get that regularly I would suggest increasing your backlash compensation by 2 * your focus step size and seeing if that “fixes” this.