Autofocusing in the sequencer

Cameras, telescopes, focusers and other hardware
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Rudi
Posts: 30
Joined: 08 Jan 2019, 04:47

Autofocusing in the sequencer

Post by Rudi » 05 Jun 2019, 07:49

ZWO is about to release their auto focuser, ZWO EAF, very soon (I think you can already buy it directly from ZWO).

https://astronomy-imaging-camera.com/product/zwo-eaf
ZWO-EAF.JPG

So I was wondering, is it possible to include auto focusing in the sequencer, for example between each filter shift?
As far as I can deduct from AA7 and the help file, it is only possible to set focuser position.
I have no experience with auto focusers what so ever, but I fear, that setting the position will no be sufficient, if there's backlash in the focus system.

Alternatively, I could probably script my way out of this?
/Rudi

fabdev
Posts: 70
Joined: 03 Dec 2018, 21:43

Re: Autofocusing in the sequencer

Post by fabdev » 05 Jun 2019, 21:46

Hello, yes, autofocus in the sequencer was added in Service Pack 1, (as an unofficial feature), see the quicknotes.pdf here: viewtopic.php?f=2&t=417

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Rudi
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Joined: 08 Jan 2019, 04:47

Re: Autofocusing in the sequencer

Post by Rudi » 06 Jun 2019, 05:08

Thanks Fabio. I missed that.
So setting focuser position to 99999 in AA7 SP1 means autofocus?

Can’t wait to get a ZWO EAF and try it out!
/Rudi

fabdev
Posts: 70
Joined: 03 Dec 2018, 21:43

Re: Autofocusing in the sequencer

Post by fabdev » 06 Jun 2019, 11:04

Yes.
Before using autofocus in sequences, just remember to set the parameters in the new autofocus window, and test them one time manually. As written in the docs, it's also important to set the best binning (the one the gives a pixel size of 15-25 microns).

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Rudi
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Joined: 08 Jan 2019, 04:47

Re: Autofocusing in the sequencer

Post by Rudi » 08 Jun 2019, 08:52

Thanks.

How does AA do the autofocusing? Does it take a picture and look at some stars FWHM, and then try to minimize them taking more pictures (V-curve)?
/Rudi

fabdev
Posts: 70
Joined: 03 Dec 2018, 21:43

Re: Autofocusing in the sequencer

Post by fabdev » 10 Jun 2019, 23:06

Hi,
it takes a sequences of images (user defined, for example 5, 7, 9) and calculates the V-curve from them.
For example, for 7 images, the focuser is moved backward for 3 "steps" and then moved forward for 7 "steps", so that 3 images are taken backward, 1 at the original position and 3 forward, all in the same "direction" to avoid backlash problems.

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