EKOS simple/relative focuser Q

[vineyard]

Hello,

Hope everyone well.  I've posted this Q on the indilib forum as well, but I thought I'd check w SGLers too in case folks have used EKOS with a DC focuser (I think what EKOS would call either a "simple" focuser or a "relative" focuser in its options?).

I've got an old TV Focusmate, and so am on the verge of getting a Shoestring Astronomy FCUSB (although maybe FLO's latest acquisition Hitecastro's DC focuser would also do the trick).  I know EKOS supports both those from the dropdown options that appear.

Has anyone used those & what have the experiences been like?  My biggest concern is that during the night, clouds come in, it can't find focus, and heads off trying to find it which takes the focuser all the way in or all the way out and I wake up to burnt out motors (or worse).  Is that a stupid concern?  (For example will the software just make the focuser go back & forth since it gets worse in all directions?  Is it possible to set an override or shutdown flag on EKOS where if HFR deteriorates too much, it just closes everything & parks?).

If that is a possibility, then I would rather just set focus at the start and leave it (the way the Focusmate works, there's an O-ring on the motor that presses against the manual focuser and that is what makes the fine focuser change - it strikes me that if during the night temperature drops (in winter!) the focuser will still stay where it is because for it to move in or out it would have to be able to turn a switched off pulse motor which is unlikely (a bit like a v strong handbrake?)?).

Cheers & stay safe,

Vin

[MarkAR]

Hi Vin, I use Ekos with a Lakeside focuser.

If it can't find focus after a number of tries it goes back to its initial position and stops everything.  It should be the same with other focusers.

[vineyard]

1 hour ago, MarkAR said:

Hi Vin, I use Ekos with a Lakeside focuser.

If it can't find focus after a number of tries it goes back to its initial position and stops everything.  It should be the same with other focusers.

Thanks Mark.   I think the Lakeside is an absolute focuser b/c its a stepper motor.  So that would definitely be "safer".

I'm trying to see if I can keep using my pulse motor Focusmate without having to get a new stepper motor.  It can certainly work as long as a human is there to override, but I'm wondering what could happen if that wasn't the case at 0200!

Cheers

[MarkAR]

Sounds like you need some software "limit switches" for max/min position. I know you can do it with the Lakeside control box but no idea if Ekos can do something similar.

[discardedastro]

On 20/06/2020 at 17:14, MarkAR said:

Sounds like you need some software "limit switches" for max/min position. I know you can do it with the Lakeside control box but no idea if Ekos can do something similar.

You can do this, but it's a lot of faff and won't guarantee the focus algorithm will succeed - the Ekos algorithms all assume a reasonably high degree of repeatability (i.e. go to 1000, go to 2000, go to 1000 and you end up at the same place plus or minus a few dozen microns). Pulse drive motors will not generally achieve this because of backlash, and Ekos has no focus motor backlash compensation (outside of the linear algorithm, but that requires good repeatability to start with before it takes up the backlash).

I'd definitely just go for a focusmotor. Swapped to the Sesto Senso last year and it's night and day from a pulse motor.

[Starflyer]

Even with an absolute focuser autofocus can be tricky to set up and get working, but once you have it working it will change your imaging so much. I'd almost forgotten how much time I wasted focusing on every filter change or losing hours of data because I wrongly assumed that my filters were parfocal.

Good luck with getting your relative focuser working.

[vineyard]

Thanks all.  I decided to try the DeepSkyDad AF3 that another SGLer was selling.  I guess I can always fall back to the original plan of an automated pulse motor alternative if that doesn't work.  Now to just try & get hold of Pavle to print a new mounting adapter (lest I have to resort to home-drilling!) - has anyone been able to contact him recently?

Stay safe,

Vin