StellarMate / EKOS / Kstars Autofocus Problem

[craigg]

Hello everyone,

I recently bought a Raspberry Pi and StellarMate.  Mostly working fine with my Atik camera, ZWO filter wheel, etc.  However, I was hoping to get the autofocus working, but having some issues.  I'm using a Hitech Astro DC focus with a Skywatcher Auto Focus motor.  This seems to be working in terms of manual focus, but when I try to autofocus it seems to get it knickers in a twist.  I have tried various INDI settings (suggestion here: https://indilib.org/forum/focusers-filter-wheels/2793-hitech-astro-dc-focuser-problem/26330.html) but what happens, even if I get it fairly close manually first is that initially it steps in and out by the increment I set (50) and you can see it getting better, and better, but then for some unfathomable reason, when nearly focused, decides to step in or out by a massive amount, so much that the focus star is no longer visible.

I just wondered if anyone has this same combination working, or if anyone has any suggestions for solving this?  My main reason for autofocus is that I currently have a mismatched set of filters so would like to automate focusing when they are switched.

Many thanks,

Craig

[wimvb]

Have you tried the indilib forum for this?

I solved a similar issue by changing the focus calculation algorithm. It should be available in the focus section of ekos.

[craigg]

No I haven't, but that's a good shout, I'll do that, thanks.

[RadekK]

Also consider presetting focus adjustment for your filters. While using Ekos CCD (the one you set up your imaging session) you can set offset for each filter (icon on the right of FW field in the first row on the tab). This way you can focus using luminance filter (offset=0) and set actual offset for various filters, which are not parfocal. You need to determine offsets first by manual focusing, but it's quite handy.

Edited March 13, 2019 by RadekK

[craigg]

Thanks Radek, however I think the Hitech Astro controller doesn't have a reliable offset - it doesn't have the position offset stored between sessions.

[rnobleeddy]

On 14/03/2019 at 16:01, craigg said:

Thanks Radek, however I think the Hitech Astro controller doesn't have a reliable offset - it doesn't have the position offset stored between sessions.

Did you ever make any progress with this? Right now I'm focusing this manually, but almost defeats the point of having got it.

[Realtimedoctor]

17 hours ago, rnobleeddy said:

Did you ever make any progress with this? Right now I'm focusing this manually, but almost defeats the point of having got it.

Try the polynomial algorithm. 

I don't have the hitech dc motor controller, but I made my own arduino which runs the skywatcher focuser. 

Had issues with it as well, too many nights of tweeking, and this is what worked/works for me. I've attached my current settings below, plus if you don't have a coma correct then I used to select full field. 

Works like a charm, though these days I barely use it. 

[rnobleeddy]

2 hours ago, Realtimedoctor said:

Try the polynomial algorithm. 

I don't have the hitech dc motor controller, but I made my own arduino which runs the skywatcher focuser. 

Had issues with it as well, too many nights of tweeking, and this is what worked/works for me. I've attached my current settings below, plus if you don't have a coma correct then I used to select full field. 

Works like a charm, though these days I barely use it. 

Thanks! I'll give that a go next time. I tried again last night with linear and whilst it seemed to run fine, it started so far away from focus that it was measuring the wrong part of the star, so ended up more out of focus!

 

Edit - is there a good reason to suspend guiding? I've just found this means the star that was chosen quickly moves out of frame, but I guess I've missed something!

Edited September 22, 2020 by rnobleeddy