Linear Autofocus Abort Issue

[Hy Murveit]

Matt,

I wrote up a little guide to contributing to Kstars (broken up into 5
posts) here:
https://indilib.org/forum/development/6171-how-to-start-developing-for-kstars.html
based on my experience and instructions I got from Jasem when I was getting
started.

In general, you send your PRs to jasem who will submit them after review or
send you back suggestions.
For things related to focus, I'd appreciate being cc'd.

This sounds like a good issue to fix. Why do you think this only affects
the Linear focus algorithm (as opposed to the other focus algorithms) or do
you think it affects all of them?
It's true that I don't think I tested for this issue when I wrote
the Linear focus algorithm.

I believe that right now Eric (TallFurryMan) is refactoring the focus
module and adding tests, and it may not be ideal to be making changes until
he sends in his refactor for review, but you can coordinate that with Jasem
and Eric.

I'm happy to answer any questions as well,

Thanks for your help!
Hy

PS, Though it'd be good to fix this, if you're looking for best focus
performance, I'd recommend using the Full Field HFR calculation, which
would not involve any star selection.

On Thu, Apr 2, 2020 at 4:30 PM Matthew Wong <snoopy_94555 at yahoo.com> wrote:

> Hello,
>
> This is my first time posting here, so go easy on me and let me know if
> I’m at the wrong place.
>
> I noticed that while using the linear algorithm for autofocus, if the auto
> select star fails, it would abort the autofocus as expected. However,
> unlike when autofocus fails to achieve focus, this abort does not return
> the focuser to its initial position. When used with the scheduler, the
> autofocus keeps retrying after failure. With enough retries, it moves the
> focuser to its stop. I’m not even sure if this is a bug rather than user
> error or faulty expectations, so I figured I’d bring it up here first.
>
> In any case, I took the liberty to read through the code on github and I
> think I found why this is happening. In focus.cpp, under
> Focus::checkAutoStarTimeout, line 2874-2876, initialFocuserAbsPosition is
> set to -1 before setAutoFocusResult(false) is called. Since the
> setAutoFocusResult is where the focuser gets returned to the initial
> position, line 2874 essentially disables this. Again, I’m not sure if this
> was done in this order for any other specific purposes, but I figure this
> is why the focuser runs to its stops whenever this happens.
>
> I’m not normally a C++ programmer outside of the occasional Arduino
> projects. I mostly work in C# on Win10, so I’m not tool-ed to test this
> readily. Hopefully, if this is indeed an issue, that this is an easy fix.
> If anyone want to help me get started on how to contribute, I’ll give it a
> shot when I get a chance. This would be my first foray into contributing to
> an open source project, so I’m unfamiliar with the procedures and
> etiquette. Again, go easy on me. Thanks!
>
> Have a good day,
> Matt
>
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