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INDI Library v1.8.5 Released (19 Apr 2020)

April 2020 release of INDI Library v1.8.5 introduces new drivers while providing fixes and improvements to existing devices and core framework.

Aborting PHD2 guiding during autofocus

2 months 2 weeks ago
hy
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Aborting PHD2 guiding during autofocus #50944
I currently guide with PHD2 (seems to work well for me, not experienced with the internal guider).
I autofocus every time I change filters, which is typically every ~30 minutes.
Honestly, my guiding and autofocus have been working reasonably well, but I've been wondering about the following:

There's a checkbox to suspend guiding when autofocusing, that I currently don't check.
My question concerns that checkbox.

If one doesn't check the checkbox (that is, if you don't suspend guiding during AF), then as I see it, that could add noise to the autofocus process (e.g. the mount might be moving during the autofocus exposure).

If one does check the box (e.g. suspend guiding during AF) then, since AF can take a couple of minutes, there's some chance the guide star will drift sufficiently such that when re-enabled, PHD2 will not be able to find the star, and PHD2 would abort guiding. (I suppose one can grow the PHD2 search region...).

What is the recommended procedure?

Hy

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2 months 2 weeks ago
TallFurryMan
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Aborting PHD2 guiding during autofocus #50966
My opinion on this is that it depends on your guider scope and setup.

You don't want the star to move. So you need to continue guiding. If your guiding setup is proper, your star will remain on the same pixel, and your main sensor will not see the corrections at all.

However, if you have an on-axis guider, it will possibly get fooled by the focus process because it is residing far from the optical center. In that case you may want to trust the mount instead and disable guiding.

-Eric

HEQ5-Pro - Atik 314E - Orion ED80T - DMK21 on Orion 50mm
DIY 3D-printed Moonlite and FWheel RGB/LPR
KStars and indiserver on two Atom 1.6GHz 1GB RAM Linux, VPN remote access

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2 months 1 week ago
DerPit
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Aborting PHD2 guiding during autofocus #51048
Well, I use an OAG, and just have no other choice than suspending the guiding. There is (at least in my focuser) quite some play that makes the star move when focus is changed. And it moves so much that PHD2 starts doing crazy things that for sure interfere with the AF routine. My mount (CEM60EC) does keep position very well without guiding, and the exact position of the stars isn't critical anyhow as I'm using the full field focus...

It usually takes a while after AF until guiding is stable again. That is why I'm not doing it automatically so far: The sequence would directly start the next exposure while the pointing is still changing. Would be nice if EKOS could always wait for an 'guiding settled' from PHD2 after un-pausing the guiding before it continues...

openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI1600+EFW+EAF+ASI290 mini

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2 months 1 week ago
hy
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Aborting PHD2 guiding during autofocus #51058
Pit,

I too have an OAG, but the focus does seem to work with the guider active. I worried about what you were saying, though, which was the reason for this thread.
I have since switched to suspending the guiding during AF, and expanded the Phd2 window to 25x25 pixels, and things seem to work as well, and I guess it makes more sense.
It probably wouldn't be hard to put in a "stall N seconds after autofocus" if you thought that would be useful.

Hy

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2 months 1 week ago
El Corazon
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Aborting PHD2 guiding during autofocus #51062
Doesn't the focus module automatically suspend guiding when it is being called?
At least that is what always happens when I am using the autofocuser.
What am I missing here?
Jo

Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set

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2 months 1 week ago
hy
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Aborting PHD2 guiding during autofocus #51064
Jo--There's a checkbox to suspend guiding (see the bottom line of the attached picture of the focus tab). If it's unchecked, it will not suspend guiding.

Pit--I noticed that in the Ekos options, under Capture (see the 2nd attachment), there's a "Guiding Settle" parameter that defaults to 0. Would that solve, or at least mitigate, your issue?
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2 months 1 week ago 2 months 1 week ago by DerPit.
DerPit
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Aborting PHD2 guiding during autofocus #51096

hy wrote: Pit,

I too have an OAG, but the focus does seem to work with the guider active. I worried about what you were saying, though, which was the reason for this thread.


Yes, it definitely depends on your focuser. Mine (Astro-Physics) is a spring-loaded R&P, and it slightly displaces the image when changing direction. With guiding running (usually) at 4s cadence and 60% aggressiveness that can easily cause corrections for 10 seconds.

I have since switched to suspending the guiding during AF, and expanded the Phd2 window to 25x25 pixels, and things seem to work as well, and I guess it makes more sense.
It probably wouldn't be hard to put in a "stall N seconds after autofocus" if you thought that would be useful.

I noticed that in the Ekos options, under Capture (see the 2nd attachment), there's a "Guiding Settle" parameter that defaults to 0. Would that solve, or at least mitigate, your issue?


Yes and no. I'm already using that one, as an additional safety after dithering. But for catching the whole settling after an AF I'd have to set it to at least 15s to be on the safe side. But as this timeout is also applied after each dither this is not an option as it would double dithering time loss :(
So I think it should really be in the re-enabling of the guiding, in a similar way as after a dither...

PS: I'm finally back at my telescope, so I can start testing things again :)

openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI1600+EFW+EAF+ASI290 mini

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