Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Peter,
You have initiated many good experiments that have not been described earlier.? Like your alternative gearboxes over 50:1.? So you are pioneering new ground.? We all benefit from your research.?
If you have the tucked motors and spring loaded worm systems then your mount is past my versions of G11 and GM8.? Alan Fang has that GM811 version and he is also investigating its behavior (or he is happy and his system is stable and in use).?
?I think this is the end result of all our systems: when we image reliably with good results we stop, lock everything down, and just drive the mount.? It's like a cake recipe.? The work goes into the recipe then the recipe is "frozen".??
One last thought: having the R4 spring in place only works if the bearing above it can slide in and out by the spring force.? If the bearing gets stuck, the spring can't level the (far) bearing. What about the bearing nearest the gearbox? I've never fiddled with that one.? Could that one have a tight spot in its race?? Would undersizing that and lubing that do any improvement?? ?I don't think that area has been tried or considered.
I'm still awaiting some bearings with ceramic balls to arrive.? Hugo in Tehachapi told me he got some amazingly smooth tracking from full ceramic bearings (they were like $50 each) but I thought there would be no way to undersize their OD, so I kept the idea of using stainless steel bearing parts.? Maybe those ceramics he got are so perfect they don't need undersizing.? Anyway ... more experiments have been tried with further progress.??
Each of us uses different scopes, different cameras... as well as different latitudes, making our comparisons somewhat fuzzy.? We can compare our unguided PE peak to peak and RMS values.? We can show our exposure subs and final images.??
On other topics: The delta variant of Covid is being seen here in the US and is now in many places the dominant strain. Hospitalizations are going up, though still under ICU capacity (except in parts of Missouri?). And the initial vaccines are starting to wear off.? And the use of masks is waning too.??
Stay well, all...
Michael
On Thu, Jul 8, 2021 at 03:46 PM, Michael Herman wrote:
All good notes and another good conversation.
?
The 80 sec oscillation has been attributed (by Michael Sinescalchi in his ) to a pinched bearing ball.? He saw either 78 or 80 seconds from that.? I appreciate that this 80 sec oscillation could arise from a 25:1 McLennan gearbox....that's new to me.??
?
If Peter has not installed a R4 Belleville spring behind his (far) RA and DEC worm bearing, he will get:
?
1. Longer Hysteresis time lag adversely affecting autoguiding
?
2. A possible pinched R4ZZ bearing ball at 78 to 80 seconds period affecting PE.
?
The solution on how to add in the R4 Belleville spring, and better quality R4ZZ bearings, and make the bearing slide and swivel in the mounting block, is written up in the attached PDF.??
?
Hope these ideas?help you get your mount to it's best operation.
?
Michael
I do have the bevel washer(s) installed per your document. It is funny but this never used to the be a problem! Only when I changed the gearboxes. But I have made so many alterations. I'm looking into it and will report back.
Peter
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Re: New G11G Looking for final tweaking advice
Nick,
Unlike David's issue, your 76 second error peak appears much smaller than the 240 second worm period error. Every G11 will have a 240 second error, as Michael said, but your 76 second peak is more residual and really should not be affecting guiding that much. I don't think any mount adjustment will be worth fussing with at this low level.
I just ran your file in PECPrep and you have the typical sinewave curve for the worm and ring gear motions. To counter this, PHD2 is working harder as the stars will appear to be moving back and forth in a sawtooth motion, and the pulses from the app must keep compensating for the periodic error. Here I would suggest downloading PEMPro for the free 60 day trail period, creating a PE curve, and uploading it to the mount. You must select Gemini Level 4/5 in the menus selections to generate the right curve. Then immediately upload the PE correction right after PEMPro has finished tracking for 40-60 minutes and is still synced with the mount. There is a wizard you can follow which is pretty simple to follow, sort of like the obvious directions in PoleMaster (see Ray's Astrophotography on YouTube for a nice PEMPro tutorial). After you upload and have PE checked in the Gemini app, you should see the PE reduced and your PHD2 RA error should drop. For PEMPro to work best your should be well polar aligned and the seeing should be good.?
After using PEMPro, then try another PHD2 run and compare to the current one. You should see a guiding improvement.
John
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Re: New G11G Looking for final tweaking advice
Hi Nick
>>>Is there a way to analyze what kind of impact this actually has on images ?? yes - look at your images. You can also do quantitative analysis such as FWHM and Eccentricity.??
?Right now, you are guiding?sub-arcsecond, which is a fraction of a pixel difference in your final images, so I suspect any additional mechanical tweaking will result in literally no difference in your images.?
Why don't you post those guiding results and your 10 minute sub on cloudy nights and see what feedback you get?? I suspect most people will say that's great result, what are you waiting for, get to imaging
I encourage you to go back to my previous post on this - this is just my opinion, but you can spend an eternity tweaking your mount in a quest for mechanical perfection with little or no practical imaging value in the end.?
There are some people who really love the challenge and want to pursue tweaking it,?and that's awesome - nothing wrong with that approach. You probably have already seen various efforts here. I'm all for it.?
If your goal is to tweak things to improve your?images, right now you do not appear to be constrained in any way by the mount given your current setup.?
Any mechanical tweaks you may want to do will still be waiting for you in the future. A lot of times with a new mount, things break in so you may find yourself with different results in 6 months
Brian
So if I somehow fix this with the same fix, what should I expect to see in PEC Prep ? That spike to disappear into the noise I suppose ?
Do you ever stop by Seattle to visit ? haha I am likely to make things a whole lot worse if I start tinkering
Is there a way to analyze what kind of impact this actually has on images ??
-- Brian?
Brian Valente portfolio
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Re: New G11G Looking for final tweaking advice
Hi Nick,
Ha ha indeed (or was that H-alpha?!)
Seattle not on my calendar anyway, but... if in California or Denver area of Colorado ....house calls may be possible....!
Generally the worm period of these mounts is quite long.? The G11 is shortest at 240 seconds.? ?The G11T is 319 sec, and the GM8 is at 480 sec.??
If the only oscillation is that or longer and hysteresis is short, then autoguiding normally solves all deep sky imaging issues.??
That's why the focus in this forum is usually on resolving any faster oscillations (gearbox at 32 sec [G11], worm bearings balls at 78 to 80 sec [G11]), and getting the hysteresis lag time (esp in DEC) as short as possible so PHD2 autoguiding can be effective and do it's magic.
Best, Michael
So if I somehow fix this with the same fix, what should I expect to see in PEC Prep ? That spike to disappear into the noise I suppose ?
Do you ever stop by Seattle to visit ? haha I am likely to make things a whole lot worse if I start tinkering
Is there a way to analyze what kind of impact this actually has on images ??
|
Re: New G11G Looking for final tweaking advice
So if I somehow fix this with the same fix, what should I expect to see in PEC Prep ? That spike to disappear into the noise I suppose ?
Do you ever stop by Seattle to visit ? haha I am likely to make things a whole lot worse if I start tinkering
Is there a way to analyze what kind of impact this actually has on images ??
|
Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
On Thu, Jul 8, 2021 at 03:46 PM, Michael Herman wrote:
All good notes and another good conversation.
?
The 80 sec oscillation has been attributed (by Michael Sinescalchi in his ) to a pinched bearing ball.? He saw either 78 or 80 seconds from that.? I appreciate that this 80 sec oscillation could arise from a 25:1 McLennan gearbox....that's new to me.??
?
If Peter has not installed a R4 Belleville spring behind his (far) RA and DEC worm bearing, he will get:
?
1. Longer Hysteresis time lag adversely affecting autoguiding
?
2. A possible pinched R4ZZ bearing ball at 78 to 80 seconds period affecting PE.
?
The solution on how to add in the R4 Belleville spring, and better quality R4ZZ bearings, and make the bearing slide and swivel in the mounting block, is written up in the attached PDF.??
?
Hope these ideas?help you get your mount to it's best operation.
?
Michael
I do have the bevel washer(s) installed per your document. It is funny but this never used to the be a problem! Only when I changed the gearboxes. But I have made so many alterations. I'm looking into it and will report back. Peter
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
On Thu, Jul 8, 2021 at 03:26 PM, Keith wrote:
What are the internal gear ratios?? In the 25:1 gearbox (P5-G11), the third stage gear ends up being 3:1 to the worm period (so 79.8s for the G11), so perhaps that's what you're seeing here.
Keith, I'm reluctant to disassemble at this point to figure that out. I too though that the 80s period might be from the gearbox. Both the 80:1 and 125:1 gearboxes do have the same gear size on the final output stage, so when I swapped them over it could have been a shared problem. If I can not find another source I'll dig into this further and get the gear ratios. I'm hoping I can neutralize it via other means. Its a good thought! Peter
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
On Thu, Jul 8, 2021 at 02:55 PM, Ray Gralak wrote:
Which build of PEMPro are you using? I'm guessing you were trying to use the ZWO ASCOM driver?
I have a ASI294MM so I am sure I can get you a version that works with that camera. Please post a ticket to this forum:
-Ray
Ray, super thanks!? I'll do as you say. Peter
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Re: New G11G Looking for final tweaking advice
Hi Nick,
See my note to Peter (PCBoreland) about the pinched ball solution.??
You did the PECprep just fine and it did show the peak as a pinched RA bearing ball.??
Finding the cause is the majority of every battle.
Michael
I don't have PEM Pro but I do have a new G11 and put my data into PEC Prep (it has been discussed on the other threads here recently)
I have no way to tell if this 76.2 error is something that's impacting me significantly or not. To me, my subs look good (at 2.2 arc sec/pxl though) although I do see RA going up/down to 1.5" or occasionally 2.0 (overall guiding is 0.5-0.6")
I am not mechanical and definitely don't want to send? my mount back, but if there is some kind of 76.2 sec error, I'd love to eliminate it now, even if it's having minimal impact on my images. I'm taking 10 min subs and to me they look good, but I am just a beginner
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
All good notes and another good conversation.
The 80 sec oscillation has been attributed (by Michael Sinescalchi in his ) to a pinched bearing ball.? He saw either 78 or 80 seconds from that.? I appreciate that this 80 sec oscillation could arise from a 25:1 McLennan gearbox....that's new to me.??
If Peter has not installed a R4 Belleville spring behind his (far) RA and DEC worm bearing, he will get:
1. Longer Hysteresis time lag adversely affecting autoguiding
2. A possible pinched R4ZZ bearing ball at 78 to 80 seconds period affecting PE.
The solution on how to add in the R4 Belleville spring, and better quality R4ZZ bearings, and make the bearing slide and swivel in the mounting block, is written up in the attached PDF.??
Hope these ideas?help you get your mount to it's best operation.
Michael
On Thu, Jul 8, 2021 at 05:29 PM, <pcboreland@...> wrote:
Use of the 125:1 gear box has removed the higher frequency Ra tracking errors. The one remaining problem is the 80s error which I have had not impact on removing, and must be related to something that I had not yet touched. I'm at a loss right now! Not sure what even causes it?
What are the internal gear ratios?? In the 25:1 gearbox (P5-G11), the third stage gear ends up being 3:1 to the worm period (so 79.8s for the G11), so perhaps that's what you're seeing here.
Keith
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Re: New G11G Looking for final tweaking advice
I don't have PEM Pro but I do have a new G11 and put my data into PEC Prep (it has been discussed on the other threads here recently) I have no way to tell if this 76.2 error is something that's impacting me significantly or not. To me, my subs look good (at 2.2 arc sec/pxl though) although I do see RA going up/down to 1.5" or occasionally 2.0 (overall guiding is 0.5-0.6") I am not mechanical and definitely don't want to send? my mount back, but if there is some kind of 76.2 sec error, I'd love to eliminate it now, even if it's having minimal impact on my images. I'm taking 10 min subs and to me they look good, but I am just a beginner 
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
On Thu, Jul 8, 2021 at 05:29 PM, <pcboreland@...> wrote:
Use of the 125:1 gear box has removed the higher frequency Ra tracking errors. The one remaining problem is the 80s error which I have had not impact on removing, and must be related to something that I had not yet touched. I'm at a loss right now! Not sure what even causes it?
What are the internal gear ratios?? In the 25:1 gearbox (P5-G11), the third stage gear ends up being 3:1 to the worm period (so 79.8s for the G11), so perhaps that's what you're seeing here. Keith
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
One big improvement was installing a rigid coupler in the RA axis. This net effect was to significantly reduced the
240s error. My raw peak-peak error is now under 3s, which corrected translated to p-p of 0.4s (0.1s rms). This is
without PEC. Sadly I have not been able to get PEMPro to work with either of my two cameras (ASI294 or ASI178),
so no way to download a PEC curve. Searching for a way to get my money back? Which build of PEMPro are you using? I'm guessing you were trying to use the ZWO ASCOM driver? I have a ASI294MM so I am sure I can get you a version that works with that camera. Please post a ticket to this forum: -Ray -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via groups.io
Sent: Thursday, July 8, 2021 2:30 PM
To: [email protected]
Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to
do this?
Thumbs up to Michael for the grease recommendation: CRC Brake and Caliper grease has MolyD, Graphite, and
Teflon. I bought it at Napa Auto Parts locally, but they had to go into the back to find it, as was not on the shelf.
Also for the hanging weight idea. I had trouble not hitting the pier, but with some creativity implemented it. I took
careful note on how Michael attached it.
I've made the upgrades I intended, but ran into some trying problems with my Dec axis. Bottom line I changed out
the coupler to one I had previously noted to find it introduced too much backlash, so went back the set screw
Oldham coupler. Backlash is at 2500ms. I think is just horrible, but likely the best that can be done with the current
worm design. Yes, it has been better, but totally hit and miss. If you take it apart again who knows what it will be?
This is the design flaw one has to live with with this mount unfortunately. I did install the 80:1 gearbox which did
make a noticeable rms tracking improvement (smaller step sizes). Dropped from about 0.8 rms to 0.4 rms.
Interestedly this is about the same level of improvement I saw with the Ra axis going to the 125:1 gearbox.
One big improvement was installing a rigid coupler in the RA axis. This net effect was to significantly reduced the
240s error. My raw peak-peak error is now under 3s, which corrected translated to p-p of 0.4s (0.1s rms). This is
without PEC. Sadly I have not been able to get PEMPro to work with either of my two cameras (ASI294 or ASI178),
so no way to download a PEC curve. Searching for a way to get my money back?
Use of the 125:1 gear box has removed the higher frequency Ra tracking errors. The one remaining problem is the
80s error which I have had not impact on removing, and must be related to something that I had not yet touched. I'm
at a loss right now! Not sure what even causes it?
Here are the raw FFT and corrected FFT for the RA axis as things currently stand. The 80s peak is 0.45s on the
second image if it is not readable. Overall my guiding with good seeing but poor transparency last night was around
0.65 rms. Previous to these modes it would have been all over the place frame to frame from 0.9ms to 2.5s,
averaging around 1.4s. The really big improvement, which has the most impact on imaging really, is how nicely the
mount performs. Smooth, no sudden transient jumps in either axis. I feel this is directly attributable to having a
higher step resolution (0.1125" in RA and 0.176" in Dec).
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Thumbs up to Michael for the grease recommendation: CRC Brake and Caliper grease has MolyD, Graphite, and Teflon.? I bought it at Napa Auto Parts locally, but they had to go into the back to find it, as was not on the shelf. Also for the hanging weight idea. I had trouble not hitting the pier, but with some creativity implemented it. I took careful note on how Michael attached it. I've made the upgrades I intended, but ran into some trying problems with my Dec axis. Bottom line I changed out the coupler to one I had previously noted to find it introduced too much backlash, so went back the set screw Oldham coupler. Backlash is at 2500ms. I think is just horrible, but likely the best that can be done with the current worm design. Yes, it has been better, but totally hit and miss. If you take it apart again who knows what it will be? This is the design flaw one has to live with with this mount unfortunately. I did install the 80:1 gearbox which did make a noticeable rms tracking improvement (smaller step sizes).? Dropped from about 0.8 rms to 0.4? rms.? Interestedly this is about the same level of improvement I saw with the Ra axis going to the 125:1 gearbox.? One big improvement was installing a rigid coupler in the RA axis. This net effect was to significantly reduced the 240s error.? My raw peak-peak error is now under 3s, which corrected translated to p-p of 0.4s (0.1s rms). This is without PEC. Sadly I have not been able to get PEMPro to work with either of my two cameras (ASI294 or ASI178), so no way to download a PEC curve. Searching for a way to get my money back?? Use of the 125:1 gear box has removed the higher frequency Ra tracking errors. The one remaining problem is the 80s error which I have had not impact on removing, and must be related to something that I had not yet touched. I'm at a loss right now! Not sure what even causes it?? ?? Here are the raw FFT and corrected FFT for the RA axis as things currently stand. The 80s peak is 0.45s on the second image if it is not readable. Overall my guiding with good seeing but poor transparency last night was around 0.65 rms.? Previous to these modes it would have been all over the place frame to frame from 0.9ms to 2.5s, averaging around 1.4s. The really big improvement, which has the most impact on imaging really, is how nicely the mount performs. Smooth, no sudden transient jumps in either axis. I feel this is directly attributable to having a higher step resolution (0.1125" in RA and 0.176" in Dec).?
?
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Re: Jerky RA drive motion
Appreciate noting that snug is good enough!
Thanks,
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Re: Jerky RA drive motion
Michael - you're the MAN!!
Minor adjustment here and the issue cannot be replicated!
Thanks - that was quick and now I'm ready for this weekend!
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Re: Jerky RA drive motion
Hi,
The most likely suspects here are the grub screws on the Oldham not being snugged down. Also know you do not need to torque the begeezus out of them, snug is plenty good enough and make sure you snug all four of the buggers or you will be repeating the exercise sooner than later.??
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Re: Jerky RA drive motion
Tom would also pull off the cover to the spur gears and watch for smooth motion on them as well
On Thu, Jul 8, 2021 at 10:56 AM, Michael Herman wrote:
Oldham coupler
I'll start there, thanks
-- Brian?
Brian Valente portfolio
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Re: Jerky RA drive motion
On Thu, Jul 8, 2021 at 10:56 AM, Michael Herman wrote:
Oldham coupler
I'll start there, thanks
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Re: Jerky RA drive motion
Hi gang,
This sounds like a case of loose setscrew(s) on one (or both) end(s) of the Oldham coupler.? These setscrews are very small.... usually taking an 0.050 inch Allen wrench.??
In the past, I've drilled and tapped these to use 4-40 thread setscrews.? The 4-40 are slightly larger but more easily driven by the next larger Allen wrench size.
Try looking there first for the trouble.
Best, Michael
Yes the clutch was tight.
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Michael Herman
Chip Louie