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On Thu, Jul 8, 2021 at 03:46 PM, Michael Herman wrote:

All good notes and another good conversation.

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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.??

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If Peter has not installed a R4 Belleville spring behind his (far) RA and DEC worm bearing, he will get:

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1. Longer Hysteresis time lag adversely affecting autoguiding

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2. A possible pinched R4ZZ bearing ball at 78 to 80 seconds period affecting PE.

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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.??

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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

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

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

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

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

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).

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).?

Appreciate noting that snug is good enough!
Thanks,

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!

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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On Thu, Jul 8, 2021 at 10:56 AM, Michael Herman wrote:

Oldham coupler

I'll start there, thanks

Yes the clutch was tight.

I'm sure you checked this, but was the clutch tight? Maybe it needs cleaning??

This was on my workbench with no equipment or weight to balance,

To clarify further, this was during the Goto and the SkyFi was not yet connected.

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