Ok finally got a chance to test my 811G last night, and honestly, not as I expected. Not as bad as 'disappointed' but not as what I 'expected'.
The DEC turned out smooth, no issues at all however the RA..... jumping up and down on PHD2 graph, worse than my eq6-r pro.
I did everything was as usual i.e. I did what I'd do if that's my eq6-r pro and PHD2 didn't report any issue/problem after calibrating but still the RA curve showed ugly and I can see that from the final 20-min sub.
Anyways, now I adjusted the RA adding very little backlash, waiting for next clear night to see if this helps.

Yue

On Mon, Jan 1, 2024 at 07:29 AM, WayBack wrote:

Michael,

Micro step position does vary but I'm not sure it represents a significant issue; this not accumulating during guiding.? The issue appearing like corrected backlash.? And it cannot accumulate in physical position between motor poles (true steps).

I always felt power consumption and the related issue of producing less torque for the power were my issues.? The benefit of being open loop becomes significant only if the weight and power allow for this.

With torque levels at tracking quite small, as you illustrate here, the variation cannot be large, or it shows up in guiding.? I've never seen anyone ask David Partridge?but the RMP of our motor during tracking must be quite low and the ability of our motor to arrive exactly on count at a moment in time also a variant.? Still there too, all just esoteric when compared to the tracking RMS achieved.? Hence the importance placed on achieving Level 6 functionality.

Doug? ?

I did not write the firmware or design these systems but my understanding of the way these system work is that they are quite different.?The way an open loop stepper drive system works vs the closed loop of the Gemini 2 servo motor drive is quite different.

A stepper motor controller like the OnStep (not the stepper driver IC which can be quite sophisticated) blindly sends the step or microstep pulses calculated and has no idea if the stepper motor has actually completed the full step count or lost steps. This is an inherent problem with an open loop stepper drive system especially a marginally powered system for the load. This means that an open loop stepper drive system cannot ever know the mount axes position with certainty. Encoders on the drive motor itself or the movement axes allows the mount controller to know with reasonable certainty the mount's position. Certainly there are encoder equipped stepper motors but they are not being exploited widely yet.?

So open loop stepper motor drive mounts using a worm screw can basically only successfully step and move the mount or lose steps and physical position but the mount controller's model is not aware and has to assume the mount? position is correct which puts the slew off target requiring the mount be recentered. Depending on the how many steps were lost and the application it may or may not matter.?

The closed loop system with encoders on the DC motor drive shaft as used in the Gemini 2 allow the controller to just run the motors and watch the encoder count slowing, then stopping or assuming the selected movement rate for tracking. Positional data for the mount is generally? known and the mount position can be corrected in the case of an under or over shoot of the desired tic count. The Gemini sends a known amount of current to the motors and watches the resulting movement through the tic counts. If the tic count is not accumulating as predicted vs time more or less current is sent as required to match the desired movement rate.?

With the rewritten PIC code and revised and tuned L6 primary controller firmware the Gemini 2 L6 firmware now has a resolution of 0.14 arcseconds. This is getting into the pretty good range IME and is 4x better resolution of the direct stepper drive G11 mount. But if you added a 4:1 reductio with a pulley you would have very similar theoretical resolution though it would still only be a guess being open loop. Adding encoders on the stepper to close the loop and correct any missed microsteps and now you have something.? ?

--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

Yep, safety limits will also do that, and I didn’t think of that option either so, double doh! Lol

You have a couple of options to take the mount off the safety limits. You can use the hand controller to manually nudge the mount away from the limit (with the diamond buttons, in the right direction away from the limit). Or you can enable an option that I don’t remember off the top of my head where it is, so a park command will nudge the mount away from the limit before issuing the command itself. I believe that option is in the gemini.net driver but may also be available on the HC. Once that option is enabled NINA should be able to park the mount, even if it’s at the safety limits.

Doh! Thanks, Jonathan. I didn't even look at the HC this morning. I just went out and checked and the mount had reached a safety limit.

Anyone,

I'm guessing here but once that limit is reached, does it completely lock out control via software until reset by the HC (i.e. is this why I couldn't park from NINA)?

Thanks,
Joel

Hi Joel,

I may not be of much help but there are a couple of things you can check. If you have your hand controller connected try issuing a park command from it. Make sure it’s not reporting a motor stall and that tracking is not set to terrestrial. If you don’t have the hand controller then use the .net ascom driver. If you haven’t rechecked your gear mesh in a few months I’m guessing the cold temperatures may be binding them. Cold temps tend to tighten the mesh, which makes them bind and then stall.?

You can safely turn the mount off and push it to CWD to start over. Just remember to use Cold Start and that you will loose any models you may have built. Speaking of which, I’d make sure the option of “sync performs additional alignment” is also turned off. Just to make sure the model is not being corrupted with too many points.

Also, make sure NINA is not changing the tracking speed. I’ve had instances where it just stops the mount but mostly after TPPA or platesolving. I don’t recall having that happen during an imaging session but it’s worth checking.

Finally, definitely upload your logs. I’m sure others can take a look and find other issues but it all goes over my head so I can’t help you with those

That’s all I can think of at the moment. Good luck

jonathan

Twice over the past week, my G11g has just stopped - not powered off, stopped. Once was during setup while I was trying to slew to a target before my session and last night about four hours into my session. My resolution for the earlier session was a full reboot which fixed the issue and it ran all night. By the time it stopped last night, I was two hours into sleep. ;)

I did not turn the mount off between the previous session (two days ago) and last night's session.

I'm having no *physical* cabling issues (i.e. entanglements causing disconnects) and the mount is still powered up. This morning it just will not respond to commands - I cannot get it to park. I hope it's not because it's about 22 F.

All other commands issued to NINA work fine - I just warmed (heh - at 22 F not much warming I can do) the camera and turned off all the equipment (except the mount which will not respond).?

I'm not sure where to begin looking for issues so I'm asking for a starting point before I turn the mount off to reset it - some logs somewhere... ???

I *know* that's not a lot of information but I'm just not even sure what to ask.

Thanks,
Joel

Even using 0.9.degree (400 step) stepper motors and the maximum possible micro steps a direct drive stepper Losmandy G11 has relatively low resolution. Once you use a.more realistic number of micro steps closer to the guidelines for reliable micro stepping somewhere between 16-32 or maybe 64 obviously resolution goes out the door. Testing steppers online for 3D printers and verified by my own testing has shown that the most reliable microstepping rate range fall between 16-32 and beyond this rate the loss of steps due to tremendously reduced torque as the microstep count goes up becomes noticeable. At least if becomes a serious issue on 3D printers anyway.?

--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

I was curious about the CQ350 but went with the EQ8-R Pro. My EQ6-R pro is now my portable mount.?

开云体育

That's what I meant.? The mount was an iOptron GEM45 and it has a 1.5" peak-to-peak oscillation in RA with a period of, if memory serves me right, something like 0.7 second.? (Since a 1.5" p-p sinusoid is only 0.5" RMS, and because the period was too fast for PHD2, it looked like maybe 0.5" of roughness and I still got good guiding.)? The motor may have been underpowered; iOptron sent me a new circuit board with different voltage regulator chips that noticeably ameliorated the problem.

Hi Mike,?

Can you explain what you mean by a "period of a full set of microsteps?" I can see that meaning the period of time it takes the motor to complete a microstepped full step. But in my example the motor is moving?3.23 full teeth a second and clearly not losing a second. Thus you must be speaking of a larger sample size.

Analog Devices' Trimanic division's has extensive efforts to deal with the situation you describe. It would be interesting to see if it shows up in the driver's diagnostic output.

-- 
Michael A. Covington, Ph.D.
Consultant, Covington Innovations, Athens, Georgia, USA 

Michael,

Micro step position does vary but I'm not sure it represents a significant issue; this not accumulating during guiding.? The issue appearing like corrected backlash.? And it cannot accumulate in physical position between motor poles (true steps).

I always felt power consumption and the related issue of producing less torque for the power were my issues.? The benefit of being open loop becomes significant only if the weight and power allow for this.

With torque levels at tracking quite small, as you illustrate here, the variation cannot be large, or it shows up in guiding.? I've never seen anyone ask David Partridge?but the RMP of our motor during tracking must be quite low and the ability of our motor to arrive exactly on count at a moment in time also a variant.? Still there too, all just esoteric when compared to the tracking RMS achieved.? Hence the importance placed on achieving Level 6 functionality.

Doug? ?

On 2023-12-31 18:06, Brendan wrote:

You can increase torque by using a larger to smaller belt hub, which is the same as any large to small gear ratio.
--
Brendan

Yes, but it remains the case that torque is not the same across the entire microstep cycle, leading to slight speeding up and slowing down.? We're not talking about lacking the torque to move the load.

Michael A. Covington, Ph.D.
Consultant, Covington Innovations, Athens, Georgia, USA

You can increase torque by using a larger to smaller belt hub, which is the same as any large to small gear ratio. ?
--
Brendan

Good info Michael.? Thanks for posting.

------------------------
Jim W
Phoenix, AZ. USA

Losmandy G11G w/ L6, NINA 3.0 / ASTAP, ASI2600MC Pro, ASI533MM Pro,?Sky-Watcher Scopes, Canon L Lenses.

On Sun, Dec 31, 2023 at 06:01 AM, @VictoryPete wrote:

What is your primary mount?

Sky-Watcher CQ350.? The G11G is my portable mount.? The CQ350 is setup at my cabin in northern AZ.? I wanted a Mach2 but decided the price was too high.

------------------------
Jim W
Phoenix, AZ. USA

Losmandy G11G w/ L6, NINA 3.0 / ASTAP, ASI2600MC Pro, ASI533MM Pro,?Sky-Watcher Scopes, Canon L Lenses.

Since the conversation has drifted to belt drives in RA, despite the title, I've changed the title.? Let me share what I learned with a mount of another brand.

Microstepped stepper motors do not have equal torque at all microsteps.? As a result, they tend to have a small cyclical error over the period of a full set of microsteps, on the order of a second (too short for PHD2 to pick up). (They get behind during the part of the cycle where the torque is lower, then catch up.)? I was able to see this in planetary videos, and of course it puts a lower limit on your guiding accuracy in deep-sky work.

Better circuit design reduces the problem but does not eliminate it.

That is why I chose a servo-motor Losmandy for my current mount. I haven't upgraded to Gemini Level 6 but am hopeful that it will become even smoother.

Belt drives like everything else have their own issues.?

LOL, so the mount is also bad at selling itself? LOL.

Try offering your "bad" mounts at market prices, not what you imagine you think they are worth during a season when people are likely to buy it. Pull down your for sale posts and put them back up in the spring at a reasonable price and they will sell.?

It doesn't help that you both have posted and complained about how bad your mounts are. Additionally posting they don't work how you think they should work and how you can't figure out how to use them unlike about 99.9% of other Losmandy owners.?

It is strange that you guys just keep on being the victims here, I think you seem to enjoy it.?

--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

On Sat, Dec 30, 2023 at 11:51 PM, Jim Waters wrote:

I gave up trying to sell my G11G.? Its my secondary mount now.

------------------------
Jim W
Phoenix, AZ. USA

What is your primary mount?