Re: Runaway slew while using PHD2
Alan
How do you have your mount limits configured? Did you use the default limit or MI-250 or did you customized them?
I had the same issue as yours and it fixed for me after I changed the mount limits from the default?
Guilherme?
On Saturday, July 17, 2021, alan137 < acfang137@...> wrote: Gemini Firmware Information
Version: 5.22
Build date: Aug 16 2018
Build time: 19:20:16
ROM size: 363400
RAM size: 960
Hand Controller Firmware Information
V1.20, Mar 12 2017, 09:30:01
What I mean was that there was no STOP button as displayed on the hand controller.
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Re: Runaway slew while using PHD2
Gemini Firmware Information
Version: 5.22
Build date: Aug 16 2018
Build time: 19:20:16
ROM size: 363400
RAM size: 960
Hand Controller Firmware Information
V1.20, Mar 12 2017, 09:30:01
What I mean was that there was no STOP button as displayed on the hand controller.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Alan,
I could only think of how to attach a laser to an axis.? I cannot think of how you'd do it on a worm.? So ...
Can you say something about what size laser you attached, and how you attached this laser to a worm??
?Do you have a photo of this?? ?Seems like you have a magic trick to teach at least to me!
Thanks again, Michael
Just as a clarification, the laser pointer trick only works when clamped to the worm or anything before it in the drivetrain.? If you clamp it to the actual axis saddle, that moves too slow to detect.? Or you have to shoot the laser beam really far away.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
It was JKmetz who recently reported this in this thread:
" And the newer?gearboxes?you can dissemble to clean and lube, or check from wear. My originals were riveted and could only be drilled out. Now they have Allen head screws which you can easily take out. If you stick your finger into the?gearbox?hole and hold down of the first gear that contacts the pinion gear, then rock the output shaft/spur gear, you can see how much play there is.
"
Stay well, Michael
Michael,
I don¡¯t know what those Allen bolt assembled gearboxes are; you must have heard about them from someone else.
Eric
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Re: G11G Guiding Performance ?
click the checkbox to show corrections
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Just as a clarification, the laser pointer trick only works when clamped to the worm or anything before it in the drivetrain.? If you clamp it to the actual axis saddle, that moves too slow to detect.? Or you have to shoot the laser beam really far away.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Michael,
I don¡¯t know what those Allen bolt assembled gearboxes are; you must have heard about them from someone else.
Eric
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Re: Runaway slew while using PHD2
Alan,
You may want to doublecheck that you actually uploaded the firmware. If you are in the Gemini Web Server, go to the page where the firmware file is indicated and see if it is the NewGem-Aug-16-2018 file. The last time I flashed the firmware, I noted there were some minor errors of omission in the posted instructions in the File section here, like hitting the Run button after selecting the file to use. (I uploaded them but didn't write them, sorry).
The PHD2 setting about "stop guiding when mount begins slewing" is meant to stop the app from flashing red, and beeping the alarm, as far as I know. Not sure how that would cause a runaway.
Then I assume you mean the Stellarium app has no Stop button. Can't advise there since I don't use it. But if you keep the Gemini app virtual Hand Controller open there should be a Stop button there to use, or keep the physical HC within reach.?
Best Regards,
John
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Re: G11G Guiding Performance ?
Can you upload the PHD2 guide log?? If your pixel scale is correct (0.8"/pixel) and this is unguided, it sure looks promising but we could tell you more with the guide log.
Keith
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Re: G11G Guiding Performance ?
Can't figure out how to increase the resolution of the picture, here's a link also...
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G11G Guiding Performance ?
In my guiding graph, DEC looks nice and smooth, but my RA is all over the place...
Is this normal for a recent stock G11G?
(I think I finally got a decent PA last night ;)
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Hi Eric,
I liked your visual approach.
Alan has told us of his innovative approach too using a laser pointer attached to an axis.? You can then readily see how long it takes to take up the time lag from hysteresis.? Just watch the spot on the wall and see how long it takes to get that to move.??
As for me, I was just trying to list all the things you have to check on as aount owner.? Like a pilot's checklist before you take off.? ?
Anyone selling or making mounts needs to have a similar quality checklist.??
My gearboxes are all the older type and all are riveted. They have some time lag.? I didn't see any lag in the McLennan ones I have but I expect all gearboxes to have some slack.? Earlier this year I went to the Losmandy company and bought two new gearboxes.? I think those are riveted too...I wasn't expecting anything different.? I'll ask if I can exchange them for the Allen bolt assembled ones you have described.? I have not seen one of those yet.? Maybe the Allen bolted ones also have a shorter lag, ...who knows.? Any product that has no spec on it will have a wide variation.??
Very best, Michael
Michael,
I replaced the gearbox on the RA axis when I first got the mount in 2013 with a McLennan gearbox, but if I remember correctly it has more backlash then the Losmandy one, so I still use the original gearbox on the Dec axis. The bulk of the backlash is due to the worm mesh anyways (no spring load on my mount), so the gearbox is not the main contributor on my mount.
Eric
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Re: How to determine mechanical CWD position?
Thanks for the reminder.? I only saw the first video but not the second one.? I'm sure there's lots of good tips.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Michael,
I replaced the gearbox on the RA axis when I first got the mount in 2013 with a McLennan gearbox, but if I remember correctly it has more backlash then the Losmandy one, so I still use the original gearbox on the Dec axis. The bulk of the backlash is due to the worm mesh anyways (no spring load on my mount), so the gearbox is not the main contributor on my mount.
Eric
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Re: How to determine mechanical CWD position?
We recommend adjusting in one direction, I'm sure you know what to do but we also covered this and other best practices for polar align in this video
On Wed, Jul 14, 2021 at 08:18 AM, Brian Valente wrote:
I'm curious what results you are getting with the Sharpcap PA process??
The sharpcap results are fine, the problem is having to adjust the alt and az back and forth a lot every time at the beginning and end of polar alignment.
-- Brian?
Brian Valente portfolio
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Re: At some point, I may begin commenting on the G11 DEC axis...
On Fri, Jul 16, 2021 at 04:29 AM, Henk Aling wrote:
Any idea what causes the positive feedback?? I've been wondering if the sampling delay could cause positive feedback if the sampling interval (exposure time) is too short especially for DEC.
Yes, but it's all speculative, so no comment.? There is no such thing as "too short exposure time" in a properly set up feedback algorithm.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
On Fri, Jul 16, 2021 at 02:17 PM, Michael Herman wrote:
That you show is typical of the stock gearbox play.? That's part #1 of hysteresis and you can't get rid of that unless you change gearbox model (to a McLennan type say). But I think all gearboxes have some hysteresis in the gearing.? (There is a spec in the McLennan types...see attached document.)
?
(...)?
?
If I left something out....I apologize.
?
For the DIY minded I would mention that OnStep requires no gearbox - the stepper is coupled directly to the worm axis.? Mode-switching stepper drivers slew the mount in slewing mode and track in micro-stepping mode.? I don't know if OnStep performs as well as Gemini but I have not seen or heard evidence of the contrary.
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On Fri, Jul 16, 2021 at 08:06 AM, John Kmetz wrote:
On Thu, Jul 15, 2021 at 04:53 PM, alan137 wrote:
Even my new G11 DEC axis has this dark grey grease on the gears, and it is smudged on the sides, so 100% sure that's the original color.
The grease under the worm blocks is also this dark grey grease.
Anybody know what this is?
The JetLube MP-50, a molybdenum grease (used at the factory on the worms), is already is a blackish grey color when originally applied. SuperLube which many are using for their relubes, is clearish or slightly off water-white. Any grease will change color over time with use with oxidation and contamination from the metals it contacts. But color is not an indicator of lube degradation, if that is what you are thinking.
No, I am just using the grease color for identification, since I am a big proponent of not mixing greases.? Here's the grease colors that my mount came with: transfer gears and under the worm blocks : dark grey on the axis spindle (needle bearings): brownish clear worm: I dunno the tint, but NOT dark grey
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Eric ("cyclone")...
Very nice work!? I love that 2 image timed video photo of the Oldham coupler end!
That you show is typical of the stock gearbox play.? That's part #1 of hysteresis and you can't get rid of that unless you change gearbox model (to a McLennan type say). But I think all gearboxes have some hysteresis in the gearing.? (There is a spec in the McLennan types...see attached document.)
On the Tucked motor system you'd find additional time lag #2 (seen by the worm movement delay from the motor) from the necessary gaps between the 2 transfer gears.? You must not allow those transfer gears to jam so there has to be a little gap.? You can adjust the gearbox mounting to optimize that.? (The gear driving the Oldham coupler is on a fixed shaft...)
On the SLW you'd get yet another time lag #3 if the OPW that's pivoting at the left pivot point can move left to right in it's "nipple" pivot hole.? That also has to have a gap.? That affects the DEC autoguiding but not normally the RA that's always forcing the RA toward the west as the sky rotates.??
( So I think that bolting down the SLW so it does not move (defeating the SLW action) is a good approach to try eliminating that time delay.? )
Another time delay #4 affects the DEC mostly too is any worm left to right slip along it's axis if the worm mounting blocks get loose.? I think these blocks must get pushed loose over mount temperature changes anyway, so I recommend putting in one R4 Belleville spring under the far worm bearing, and reducing that bearing OD and lubing it to slide, to get rid of that time delay.
{ The G11T has 3 transfer gears at the RA Titan worm drive.? I found that a 2 pulley belt drive eliminates that time delay in those gears (that thanks to Allan Ruckle who showed me his nice implementation).? }
Then there is the worm to ring gear gap.? That was always the obvious place where a gap must be optimized....going back decades.? For that, we used to (and I still do) use spark plug feeler gauges to adjust that.? That's hysteresis element #5.? Many owners get rid of that gap by using a weighted cord wrapped around the axis. [On the RA axis, hang the weight to the East side to minimize chatter of the ring gear when the worm rubs it perpendicularly].?
Recent emails suggest on some units there could be a gap between the 1.25 inch shaft and the needle bearing ID.? I don't find that only units but it's another thing to test for.? I guess that is potential hysteresis element #6.?
Lastly, check that your dovetail mounting at the top of the DEC axis bolts are tight and that dovetail is not able to wobble.?
If I left something out....I apologize.
Have fun all,
Michael
How do I do that?
As briefly described in my previous post, I measured the backlash directly by taking pictures of the coupling. To be more specific:
-Remove the motor-gearbox assembly from the mount. Keeping half the coupling on the gearbox output shaft helps with the backlash measurement.?You should be able to rotate the output shaft with your fingers and feel the backlash.
-Take a pictures at each end of the backlash. I installed my camera on a tripod so I can easily align the images. The camera was facing the end of the shaft (or coupling half).
-In Photoshop, or other imaging software, measure the angle difference between the 2 images; this is the gearbox backlash. Convert the measured backlash to other units, for instance:
Backlash angle * 239.34 /? 360 deg = backlash in seconds at sidereal rate
-For the worm backlash, repeat the above taking pictures of the other coupling half on the worm which is still installed on the mount.
-If you believe there is backlash in the coupling itself, you could assemble the coupling, fix one end, and measure the backlash at the other end using the same approach.
Here is an example of the two pictures for the gearbox backlash, combined in a gif file:
Eric
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
How do I do that?
As briefly described in my previous post, I measured the backlash directly by taking pictures of the coupling. To be more specific: -Remove the motor-gearbox assembly from the mount. Keeping half the coupling on the gearbox output shaft helps with the backlash measurement.?You should be able to rotate the output shaft with your fingers and feel the backlash. -Take a pictures at each end of the backlash. I installed my camera on a tripod so I can easily align the images. The camera was facing the end of the shaft (or coupling half). -In Photoshop, or other imaging software, measure the angle difference between the 2 images; this is the gearbox backlash. Convert the measured backlash to other units, for instance: Backlash angle * 239.34 /? 360 deg = backlash in seconds at sidereal rate -For the worm backlash, repeat the above taking pictures of the other coupling half on the worm which is still installed on the mount. -If you believe there is backlash in the coupling itself, you could assemble the coupling, fix one end, and measure the backlash at the other end using the same approach. Here is an example of the two pictures for the gearbox backlash, combined in a gif file: Eric
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Michael Herman