Maybe confused the autofocus routine by not allowing enough out focus limit?
See log entry below
See the HFR 1.49 @ 11939, error out because cannot move past limit then HFR 7.07 at 11940
[2021-05-11T20:31:21.090 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR 1.76 @ 11855. Delta (63.3%)"
[2021-05-11T20:31:21.100 PDT INFO ][ org.kde.kstars.ekos.focus] - "Focusing outward by 115 steps..."[2021-05-11T20:31:24.709 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR 1.76 @ 11970. Delta (63.7%)"
[2021-05-11T20:31:24.719 PDT INFO ][ org.kde.kstars.ekos.focus] - "Focusing inward by 54 steps..."[2021-05-11T20:31:27.767 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR 1.49 @ 11916. Delta (37.1%)"
[2021-05-11T20:31:27.778 PDT INFO ][ org.kde.kstars.ekos.focus] - "Focusing outward by 23 steps..."
[2021-05-11T20:31:30.828 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR 1.49 @ 11939. Delta (36.8%)"
[2021-05-11T20:31:30.838 PDT INFO ][ org.kde.kstars.ekos.focus] - "Focusing outward by 31 steps..."
[2021-05-11T20:31:33.896 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR 1.24 @ 11970. Delta (11.9%)"
[2021-05-11T20:31:33.926 PDT INFO ][ org.kde.kstars.ekos.focus] - "Focuser cannot move further, device limits reached. Autofocus aborted."
[2021-05-11T23:47:50.623 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR 7.07 @ 11940. Delta (594%)"
[2021-05-11T23:47:50.700 PDT INFO ][ org.kde.kstars.ekos.focus] - "Focusing outward by 200 steps..."
[2021-05-11T23:47:54.306 PDT INFO ][ org.kde.kstars.ekos.focus] - "FITS received. HFR -1 @ 12140. Delta (807%)"
[2021-05-11T23:47:54.308 PDT INFO ][ org.kde.kstars.ekos.focus] - "No stars detected, capturing
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Hi Ron,
You are correct, setting to half step should move only half the distance for a given count.
What does it mean "wave mode did nothing at all' ?
As far as distance moved, wave and full should be identical, it is just how the phases of the motor are energized that changes.
If interested in how the motor is controlled, see the charts on phases energized based on wave/full and half (in the chart, nstep full = two phase on stepping).
Simple steppers
I just did the half/full and wave on my unit with nstep and it worked as expected with half step = half distance for same count.
What is your phase wiring set to, default is '0'
Which version of nStep do you have (a picture is worth a thousand words 
Gene
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Hi Ron,
Half stepping will double the number of steps, so if you are using wave and have focus at 51k steps, this would now be 102k steps if racked in then moved to focus position.
Half stepping has less torque but finer granularity.
For your focus run, I am not an EKOS user but 134 frames seems quite excessive.
I advise playing around with the initial step counts in Ekos, if you find 20 to 40 causes a change then start with 100 or 200.
From your graph it looks like you were chasing seeing turbulence. About what intensity was the chosen star to focus on? I believe Ekos help says mag 3 or 4 star but that is so dependent on aperture, exposure length, camera sensitivity. Given any specific exposure duration, try manually picking a star that has about 50% to 75% full well when close to focus at a given exposure length and for sure not saturated or too dim.
Gene
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Hi Mohamed,
If all the focus runs were done without changing filters and same star, looks really strange.
All reverse/no reversed should be the roughly the same values for -every- focus run and -not- be different by 2500+ steps difference between runs 1 and run 6
The '43' was actually the 2500 steps difference translated to stepper motor output shaft rotation difference in degrees betweens runs 1 and run 6.
Gene
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Hi Mohamed,
Your iterations show decreasing position numbers for both forward and reverse, the delta's.
Is each set of measurements made with a different filter or just different focus runs?
Looking at the numbers
8910 - 6328 = 2582/4 = 645.5 *degrees/step(0.067) = 43.2485 degrees output shaft movement
8651 - 6119 = 2532/4 = 633 *degrees/step(0.067) = 42.411
Where the /4 is your 1/4 stepping and 0.067 from your 27:1 motor/gearbox reduction
Gene
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Hi Mohamed,
Thanks!
For the 'steps/second' part of the question, when you did the testing, on the Main tab of the driver, what value did you have for 'Speed' Focus Speed?
Source code allows values of 0, 1 or 2
Which looks to directly correspond to Slow or Medium or Fast
as defined in the documents on sourceforge myFP2-307-3.pdf
Had you done any tuning of the motor speeds as given in the document section
FINE-TUNING THE STEPPER MOTOR SPEED
?
Did you happen to try the backlash experiment at different speeds or different stepping, which you mentioned was set to 1/4 step?
This is one area that can cause strange results, how fast driving based on chosen step mode, just looking to rule it out.
Another dealing with stepping is power supply to the phase coils of the motor drooping.
ALT: With your angle of 40-50 degrees, this would seem to present leverage on the drawtube when changing directions, giving it a chance to tilt.
Gene
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Hi Mohamed,
This is on your WO Z61 with focuser motor under comtrol of the MyFocuserPro2?
How fast are you driving (steps/microsteps per second)? What type of stepper motor.
Drive too fast and miss steps, not enough motor torque and miss steps.
Not all clamped down on the shafts and slippage as Peter mentions.
What was the orientation of the scope, high alt, low alt ?
Gene
PS: For my video, sorry, it was meant to show a low repeatable backlash stepper motor gearhead.
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Following up on the dmesg_output.log
You can open and read the contents with any text editor, vi,,,,
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Hi NorthMIPaul,
Good on not changing after powerup!
Would not need the dmesg unless they were changing.
dmesg:
When you typed
dmesg >/tmp/dmesg_output.log
This created a new file in your /tmp directory
After running the above, do
ls -ltr /tmp/dmesg_output.log
You should see the new file.
Gene
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Hi NorthMIPaul,
Would need to see the full output from dmesg.
Try a
dmesg >/tmp/dmesg_output.log
And attach the file /tmp/dmesg_output.log
As far as USB enumeration, when powered up devices may enumerate to a different TTY, the big problem comes about when they re-enumerate after initial enumeration but -not- because of an unplug/replug. Dmesg output should provide some clue for the second part.
Which of the above are you seeing? Different TTY when power up but device stays where it starts or changing after having a value at powerup?
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Hi NorthMIPaul,
How are you powering your USB?
Direct from motherboard, un-powered hub, powered hub?
If power is drooping too low on the USB interface, devices will re-enumerate which may explain what you are seeing.
What does dmesg show, are devices coming and going?
Gene
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Hi anderskvist,
What type of scope are you using SCT, refractor, etc?
Any idea of approx AZ of M81 when image was taken?
Do you have any flex between guide and main scope?
I took your image and did a plate solve on it, shows about 30arcsec of 'tadpoles', see attached.
This looks like a 'jump' happened.
When image starts, has slew and guider been stable for a number of seconds prior to image taking?
Gene
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Hi Mohamed,
True backlash in opposite direction can vary but more than likely comes from drawtube tilting than gear train backlash, which is more repeatable -if- the gears are fixed to the shaft and do not ride on the shaft they are mounted to. Coming from drawtube tilt also implies amount may change depending on how far the drawtube is extended.
Here is a video I did of a stepper motor head used, gears only in the head. Repeatability is good considering any slip that may have occurred of the dial indicator on the moment arm and the 5 pound weight hanging from the 2 inch moment arm
Stepper motor head video from 2012
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If the focus routine always moves to final position in the same direction then oversizing the backlash steps when reversing basically makes it a do not care because the backlash cancel's out.
Think about it this way, currently at 500 with actual backlash = 25
Move back 200 physically moves it to 325 (175 = 200 - 25 backlash), counter though shows 300
Move forward 200 (physically moves 175 = 200 -25 backlash) up to 500 physical and counter shows 500
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