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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

For those with focus issues

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Well that certainly fits any definition of "out of focus"! (is that the SCT? Looks maybe out of collimation, as well - but I am *really* not an expert in that realm)
Surely you could see in the focus tab display that you would up with donuts instead of stars (but that doesn't help if you're trying to automate).

When I first started autofocusing I made the mistake of tightening the 'regular' tension adjustment on the focuser, and all kinds of horrible things would happen, mostly related to the stepper motor reporting it had moved but the focuser was still really in the same place (different system, though - I use a Rigelsys NStep).

"Far from clear what the bottom of the curve is" makes me first think to suggest increasing the initial step size. You might (should, really, as long as you are experimenting) also try increasing the exposure time and averaging over 2 or 3 frames - though I still get "bouncy" curves with 2 or 3 frames when the seeing is poor.
2 years 2 months ago #79813

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Ron,

Just to be clear, that image is high level zoom at some dim stars. The bigger stars just look bloated, which is what got me looking at the image in more detail.

I don't think it's collimation, as the circle would be lopsided... although it is a bit isn't it? I looked at my images from two nights ago and they had pretty good stars... so don't think it's the scope.

I'll check the lock knob and make sure it's loose... but pretty sure it's okay.

When I test tonight, I'll also try setting the step higher. Unfortunately, the seeing tonight is not supposed to be as good.

Thanks,

Ron
2 years 2 months ago #79814

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Replied by Giles on topic For those with focus issues

Lack of collimation might throw the focusing out, maybe focus at bin x2, or collimate your scope for the future !!
2 years 2 months ago #79815

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Giles,

Good thoughts!

Thanks!

Ron
2 years 2 months ago #79816

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Re Ron Debry's question about "Solution Pending" and also re @Ron Clanton's point about "selecting different stars in each iteration":

I made some changes to Linear focus in October 2021, so they would have been released as part of 3.5.6 and later that affected those two things.

Pending: The scheme prints "Pending" on the focus graph once it is in its 2nd pass and has found a position with an HFR that is "good enough to complete" (e.g. within the tolerance of the best HFR from the first pass). It is greedy, though, and keeps sampling positions/HFRs until it stops measuring lower/better HFR values. When it does stop seeing improvement, it will try again in that same position a few times. After a few failures to improve it stops, otherwise it keeps sampling and moving. In this 2nd pass it is using step_size/2, and once it passes the 1st pass' min position it uses step_size/4. Once you see the "Pending", it is guaranteed to stop and not fail. 

Selecting different stars. I too wondered if using different stars for HFR comparisons was adding noise to the scheme. Therefore, I made a change such that, when it compares HFR values from two focus images, it only uses stars from the same image coordinates in both images to make that comparison, if at all possible. Note, that the stars displayed on the the focus image, with HFR values reflect the star detections from StellarSolver, but may/may-not be used to compare the HFR values with a previous image.

You can find a more detailed description of the changes and pointers to the code here:
invent.kde.org/education/kstars/-/merge_requests/458
 
The following user(s) said Thank You: Giles
2 years 2 months ago #79817

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Hy,

Thanks for the explanation.

Your star selection process sounds like the correct way to do things... the visual made me think differently.  So that eliminate the need to unselect full field processing.

Regarding the "pending" process... After the second pass, is it still using a linear process?  It's hard to tell on my screen because the numbers are all over the place... but hopefully each pass would begin by moving an exaggerated amount and returning to remove backlash.  Is that correct?

If it's doing things correctly, then I may have to start looking at something else... poor target, collimation, step size, etc.

Thanks!

Ron
2 years 2 months ago #79818

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Replied by Giles on topic For those with focus issues

I think you have a collimation task ahead of you.

If it is any consolation, the JWST team have the same task, but they're collimating 16 secondary mirrors against a single primary.
 
Last edit: 2 years 2 months ago by Giles.
2 years 2 months ago #79820

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Ron,

Yes, the 2nd pass begins, just like the first, with the focuser moving out and then back in to try to remove backlash. You should be able to see the focuser movements in the logs, or in the log box at the bottom of the Focuser Tab.

There is quite a bit of noise in the HFR calculations for reasons I don't full understand. Perhaps it's seeing, perhaps it's image noise affecting the star extraction scheme, etc. I had hoped my scheme to use the same stars to compare images would remove all that, but when I was testing that change, as I recall, I found some improvement, but I believe the majority of the "HFR noise" remained. 

More detail on the first point. I just ran Linear autofocus using the simulator profile, and below are the lines in that log box at the bottom of the Focus Tab. I've highlighted in red lines at the start of the first and 2nd passes that show the focuser moving out then back in.

Hy

2022-01-23T13:01:29 Focus procedure completed after 19 iterations.
2022-01-23T13:01:29 Detection complete.
2022-01-23T13:01:29 Detecting sources...
2022-01-23T13:01:29 Image received.
2022-01-23T13:01:27 Capturing image...
2022-01-23T13:01:24 Detection complete.
2022-01-23T13:01:24 Detecting sources...
2022-01-23T13:01:24 Image received.
2022-01-23T13:01:22 Capturing image...
2022-01-23T13:01:19 Focusing inward by 500 steps...
2022-01-23T13:01:19 Detection complete.
2022-01-23T13:01:19 Detecting sources...
2022-01-23T13:01:19 Image received.
2022-01-23T13:01:17 Capturing image...
2022-01-23T13:01:14 Focusing inward by 1,000 steps...
2022-01-23T13:01:14 Detection complete.
2022-01-23T13:01:14 Detecting sources...
2022-01-23T13:01:14 Image received.
2022-01-23T13:01:12 Capturing image...
2022-01-23T13:01:08 Focusing inward by 1,000 steps...
2022-01-23T13:01:08 Detection complete.
2022-01-23T13:01:08 Detecting sources...
2022-01-23T13:01:08 Image received.
2022-01-23T13:01:06 Capturing image...
2022-01-23T13:01:03 Focusing inward by 1,000 steps...
2022-01-23T13:01:03 Detection complete.
2022-01-23T13:01:03 Detecting sources...
2022-01-23T13:01:03 Image received.
2022-01-23T13:01:01 Capturing image...
2022-01-23T13:00:58 Focusing inward by 1,000 steps...
2022-01-23T13:00:58 Detection complete.
2022-01-23T13:00:58 Detecting sources...
2022-01-23T13:00:58 Image received.
2022-01-23T13:00:56 Capturing image...
2022-01-23T13:00:52 Focusing inward by 10,000 steps...
2022-01-23T13:00:49 Focusing outward by 20,923 steps...

2022-01-23T13:00:49 Detection complete.
2022-01-23T13:00:49 Detecting sources...
2022-01-23T13:00:49 Image received.
2022-01-23T13:00:47 Capturing image...
2022-01-23T13:00:44 Focusing inward by 2,000 steps...
2022-01-23T13:00:44 Detection complete.
2022-01-23T13:00:44 Detecting sources...
2022-01-23T13:00:44 Image received.
2022-01-23T13:00:42 Capturing image...
2022-01-23T13:00:38 Focusing inward by 2,000 steps...
2022-01-23T13:00:38 Detection complete.
2022-01-23T13:00:38 Detecting sources...
2022-01-23T13:00:38 Image received.
2022-01-23T13:00:36 Capturing image...
2022-01-23T13:00:33 Focusing inward by 2,000 steps...
2022-01-23T13:00:33 Detection complete.
2022-01-23T13:00:33 Detecting sources...
2022-01-23T13:00:33 Image received.
2022-01-23T13:00:31 Capturing image...
2022-01-23T13:00:27 Focusing inward by 2,000 steps...
2022-01-23T13:00:27 Detection complete.
2022-01-23T13:00:27 Detecting sources...
2022-01-23T13:00:27 Image received.
2022-01-23T13:00:25 Capturing image...
2022-01-23T13:00:22 Focusing inward by 2,000 steps...
2022-01-23T13:00:22 Detection complete.
2022-01-23T13:00:22 Detecting sources...
2022-01-23T13:00:22 Image received.
2022-01-23T13:00:20 Capturing image...
2022-01-23T13:00:16 Focusing inward by 2,000 steps...
2022-01-23T13:00:16 Detection complete.
2022-01-23T13:00:16 Detecting sources...
2022-01-23T13:00:16 Image received.
2022-01-23T13:00:14 Capturing image...
2022-01-23T13:00:11 Focusing inward by 2,000 steps...
2022-01-23T13:00:11 Detection complete.
2022-01-23T13:00:11 Detecting sources...
2022-01-23T13:00:11 Image received.
2022-01-23T13:00:09 Capturing image...
2022-01-23T13:00:05 Focusing inward by 2,000 steps...
2022-01-23T13:00:05 Detection complete.
2022-01-23T13:00:05 Detecting sources...
2022-01-23T13:00:05 Image received.
2022-01-23T13:00:03 Capturing image...
2022-01-23T13:00:00 Focusing inward by 2,000 steps...
2022-01-23T13:00:00 Detection complete.
2022-01-23T13:00:00 Detecting sources...
2022-01-23T13:00:00 Image received.
2022-01-23T12:59:58 Capturing image...
2022-01-23T12:59:54 Focusing inward by 2,000 steps...
2022-01-23T12:59:54 Detection complete.
2022-01-23T12:59:54 Detecting sources...
2022-01-23T12:59:54 Image received.
2022-01-23T12:59:52 Capturing image...
2022-01-23T12:59:49 Focusing inward by 2,000 steps...
2022-01-23T12:59:49 Detection complete.
2022-01-23T12:59:49 Detecting sources...
2022-01-23T12:59:49 Image received.
2022-01-23T12:59:47 Capturing image...
2022-01-23T12:59:42 Focusing inward by 10,000 steps...
2022-01-23T12:59:41 Focusing outward by 12,000 steps...
2 years 2 months ago #79821

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Hy,

I was referring to the your description of  "Once it passes the min position..." If it doesn't find a better solution, how does it get back to the min position?  Hopefully by moving back an exaggerated amount and then moving back to it (thus eliminating backlash)?

I know I'm reaching...

Thanks,

Ron 
Last edit: 2 years 2 months ago by Ron Clanton.
2 years 2 months ago #79822

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Giles,

LOL!  Perhaps!

I'm not convinced that it's the cause of my focusing issues... but I'm also checking it tonight.

Ron
Last edit: 2 years 2 months ago by Ron Clanton.
2 years 2 months ago #79823

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It does not move back after the 2nd pass. It stays where it is and ends.
2 years 2 months ago #79824

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Hy,

Forgive me... I'm not sure that I understand the process. In my words:

First pass: Moves out an exaggerated amount, moves in to the multiple of initial step. (My case 5 x 20 steps) It identifies minimum HFR spot.

Second pass: Moves out an exaggerated amount, move in to the multiple of 1/2 step (5x10) from minimum HFR spot. It measures each stop's HFR until it reaches the first pass minimum, then continues past this spot at 1/4 step. Per your comment: "In this 2nd pass it is using step_size/2, and once it passes the 1st pass' min position it uses step_size/4".

So if it fails to find a better HFR once it passes the 1st pass' min position... how does it return to that spot?

Does my question make sense?

Thanks,

Ron
2 years 2 months ago #79825

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