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Okay so last night was a good night and I think I got a lot accomplished with good seeing. Attached is a guide log for PHD2. I did a calibration, guiding assist and guided/unguided runs then experimented a bit.
First thing I did was what Brian V had in his post about adjusting spring-loaded worms. I set the spring length between the spacers to the 8.5 mm. Then I use the other screw to dial in when the gears caught.
Still would like clarification on whether the correct setting is when the gears just start to feel tighter or when they actually grab tight. A little bit of give both ways leaves some questions.
I still have the 76 second problem I need to work on which seems to be holding back potentially exceptional guiding.
Once I finished the standard calibration and runs I noticed, as previously, one second PHD2 guiding seems to work best. It may be because of better-than-average seeing.
Later on in the evening I did some longer runs and tried the PPEC in PHD2.? WOW!! After a little bit it really seemed to make the mount work great.
Still held back by that 76 second anomaly. I'm attaching a picture that shows if I could get the RA under control guiding would be much better.
Tonight I was using a reducer lowering my focal length to 644 mm from 805 mm. Much rather run at 805 mm for galaxy photography.
So here are my questions:
What's the best way to get rid of the remaining DEC backlash I have? Is it adjusting the little back off screw next to the spring-loaded screw?
The above question about setting the gears whether just starting to feel tighter or when they actually grab tight.
I downloaded Prempro, and I'm a little intimidated. Should I just follow the Gemini 4 instructions on the Prempro documentation online?
I really want to purchase the software if it's going to work even better than PPEC in PHD2.
Is there a better guide out there on how to do this with a G11G Gemini II?? Kind of step-by-step?
Can PHD2 PPEC be used in conjunction with a mount based PEC curve to increase the elimination of the 76 second anomaly?
I really don't want to touch the worms, because it's guiding halfway decent now.
Is there anything that can be done with that set screw next to the spring-loaded screw to help the RA guiding?

That's all I can think of for now, stayed up all night, worked this morning and now for a nap so I can go out all Saturday night.
So I hope everything makes sense, little sleep deprived right now.

Thanks in advance for all the help!
Any advice is appreciated, whether I did a idiot move or not.

David Malanick

David, I found some ABEC 5 bearings on EBay, 5 for $10.64. Item number 25149579011. They will likely greatly reduce the bearing fundamental. They did a great job for me. What where your Ra/Dec values over sat 30 min plus period? You can read your PHD logs and do frequency analysis using PHD2Log Viewer if you have not already discovered it.

Peter

Hi All,

I seem to keep repeating the same thing over and over regarding the 76 second PE bump but people don't seem to know how to find this information here in the groups. I didn't invent this but I was doing this same modification on HEQ5/Sirius and EQ6/Atlas mounts almost 10 years ago as part of my EQMOD lunacy period.?

The Losmandy mount 76 second PE bump is not caused by bearing quality so much as how the worm bearing are installed, in other words bearing grade has nothing to do with the 76 second PE bump. The well known solution for this problem is simple, take out all axial play and preload the worm bearings axially by adding a correctly sized and oriented Belleville disc spring. Alternately you can use a Buna-N O-ring in the right size to provide the required preload. In both cases you need to eliminate the interference fit of the bearing shell and bearing support.?

An additional method which is less reliable but can be made to work is to clamp the outer bearing block axially and then fasten the block in the OPW channel. Works but can be hit or miss.?

This is an engineering issue well covered in several different bearing manufacturer's white papers. Google it, it is no secret that bearing preload is recommended for precision assemblies. For Losmandy mounts Michael Herrman long ago collaborated with me and he wrote a nice paper on it which is located in the group files section.??

The easiest method is to reduce the outer bearing shell by using a drill to turn the bearing with a fine stone or emery paper and add some grease to promote free movement of the bearing in the bearing block. When reassembling the right side or outer bearing and bearing block you must preload the outer bearing shell NOT the inner part of the bearing as was shown in Michael Herman's paper. The idea is that by preloading the outer bearing shell the force path is from the outer bearing shell and grooved ball race, to the bearing balls, to the inner bearing race, to the worm, to the? motor side inner bearing race, to the balls, to the outer grooved race and outer bearing shell to the motor side bearing block. This is the not so secret to eliminating the 76 second PE bump.??

SORRY FOR THE EDIT AND REPOST!?

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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

oh i forgot to add an easy to understand link;??
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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

Chip, Bearing grade I think has a lot to do with the tolerances that affect the seating in the one piece worm (oxymoron) blocks a relative to the relative worm shaft, and if there is play.? At least I found this to be the case. Preloading is key and I did read Mark's paper on various ways this can be done. Is this the one you are referring to or is there another document? Interesting you are arguing for a looser fit of the bearing and the shell. I need to read this document I think. It's important that we stand on the shoulders of other who have been through this time loop before.?

Peter

On Sat, Jun 19, 2021 at 12:48 PM, <pcboreland@...> wrote:

Chip, Bearing grade I think has a lot to do with the tolerances that affect the seating in the one piece worm (oxymoron) blocks a relative to the relative worm shaft, and if there is play.? At least I found this to be the case. Preloading is key and I did read Mark's paper on various ways this can be done. Is this the one you are referring to or is there another document? Interesting you are arguing for a looser fit of the bearing and the shell. I need to read this document I think. It's important that we stand on the shoulders of other who have been through this time loop before.?

Peter

Peter,

The ABEC bearing grades have nothing to do with external dimensions. The ABEC grade is a standardized set of internal bearing tolerances. The normal commercial bearing grade is ABEC-3

If your new bearings were supposed to be ABEC-5 and they fit no? friction into the bearing blocks those bearings are probably junk.

??
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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

Hi David,

Was just looking through your log with PECPrep and this looks like a guided run. For a good mount analysis you need to restart PHD2 and do unguided output. Here you must exit PHD2, not just close it. Then restart and select a star, but uncheck use guided output, and also make sure the Gemini PEC box is unchecked. Run about 30-40 min. and exit again when you are done. That way you can see how the periodic error and other anomalies look uncorrected. Sorry if this was not explained earlier.?

Just looking at your? PHD2 screen shot, your scatter plot looks well centered and the total error was around 0.5 if I am reading the fine print correctly. But the RA seen here looks like it is see-sawing, suggesting a PEC curve may be needed. But this is hard to say with one screen. You need to observe over time. Please see attached doc on how to look at logs. If you are seeing a 76 error a PEC curve does not help as the period will not repeat and overlay the worm period; with each cycle the peaks and valleys between PE and 76 sec. will always differ. Many here have redone their worm blocks and bearings to change this error as Chip said. But I think you said this was a new mount so you probably don't want to rebuild and experiment which will void warrantee. I don't have the spring loaded worms so I can't advise on which adjustments might help here. Suggest you stay in touch with Brian V. on this.

PEMPro is pretty intuitive to use if you follow the Mount Wizard in the upper drop down menu. I think this software is still free for the first month or two of use. You can check out the Losmandy video on the subject for a good tutorial. PEMPro will let you upload the PE correction curve right to the mount and you can see if guiding is improved with PEC Off vs PEC On. With a good PEC curve PHD2 doesn't have to work as hard to make adjustments. But if your 76 second error is large this still presents a challenge.

John

Thanks for all the help so far. I went out Saturday night and tried Pempro. Really less intimidating than I thought. Was actually hoping to train a full seven worm cycles, however the random clouds moving across the sky really did not help at all.
Hopefully I can try Pempro again and get some good PEC runs Monday night.
I really appreciate the help on the 76 second error, however the mount is brand-new and under warranty and I really don't want to start tearing it apart yet.
On a night I had really excellent seeing, shooting 30 second subs, I could really tell where the 76 second error showed up. It was like lucky imaging, couple good subs couple bad subs, throwing out about 30% to 40% of subs.
Tried 60, 120 and 300 second subs, that little RA jump really adds up, unacceptable imaging.
If anyone with spring-loaded worms could give a shout out on how they got their final setting tuned in, please let me know.
I'm interested in getting that 1400 to 2500ms backlash toned down a bit. Doesn't affect guiding that bad, just annoying that other people can get it so low.
Wondering how to adjust that back off screw next to the spring. If that is what is needed.
Hope hope the weather will be clear enough soon that I can do another proper PHD2 long guided and unguided run for data.
I seem to have the worms adjusted a lot better than they came on delivery, probably that bumpy FedEx truck and that dandy driver that tried carrying four boxes in one trip and joked about "Looks like they might not make it all to the front porch without falling off the hand truck" when I took delivery.

Has anyone ever gotten an official fix or statement about the 76 second error.
I did start a ticket with support but never got a reply back.
$4000+ is a lot of money to spend if I have to do a do-it-yourself repair and hope that cures it.
Starting to wonder if I'll have to send the mount back to have new bearings and the worms "properly and correctly" adjusted.
Maybe it's just a glitch when the mount was assembled, something out of alignment or too tight or loose.

Thank you,
David Malanick

Your screenshot is not very useful because the groups.io resized it down far enough that it's hard to read.
Anyway, you have 76 second periodic error just like me, and also everybody else.
PEC will not fix it.
There are a few possible ways to address it:
0) Send it back to Losmandy.? Get it back in an unspecified amount of time.
1) Reset the bearing blocks, as per Losmandy's Youtube video.? Maybe the block will realign and this error will be reduced.
2) Shim the block to change alignment (too much trial and error)
3) Michael Herman Belleville washer fix.? (This was the solution that finally worked for me)

As for DEC backlash, I have a very long post about how to adjust it
/g/Losmandy_users/message/71205

At one point I had the 76 sec cycle.? Reading up, it was a misalignment issue.? Mine was caused by a DIY SLW design.? I switched to a different DIY design where both blocks were aligned by screwing them against the cover plate, with no play by squeezing them manually while screwing them tight.? This resolved it.

On Sun, Jun 20, 2021 at 03:48 PM, Henk Aling wrote:

At one point I had the 76 sec cycle.? Reading up, it was a misalignment issue.? Mine was caused by a DIY SLW design.? I switched to a different DIY design where both blocks were aligned by screwing them against the cover plate, with no play by squeezing them manually while screwing them tight.? This resolved it.

Henk,?

The squeezing of the blocks resolves the 76second issue by making the bearing balls rotate with the worm. This is what preloading worm bearings with the Belleville disc or a properly sizes Bunny O-ring.which does the same thing. This is a well known and tested way to resolve this issue and no secret just not understood by most.?
?
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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

On Sun, Jun 20, 2021 at 05:22 PM, alan137 wrote:

Your screenshot is not very useful because the groups.io resized it down far enough that it's hard to read.
Anyway, you have 76 second periodic error just like me, and also everybody else.
PEC will not fix it.
There are a few possible ways to address it:
0) Send it back to Losmandy.? Get it back in an unspecified amount of time.
1) Reset the bearing blocks, as per Losmandy's Youtube video.? Maybe the block will realign and this error will be reduced.
2) Shim the block to change alignment (too much trial and error)
3) Michael Herman Belleville washer fix.? (This was the solution that finally worked for me)

As for DEC backlash, I have a very long post about how to adjust it
/g/Losmandy_users/message/71205

?alan137,
I have read your post and my backlash is similar to what yours is showing as very good worm mesh in the picture. Maybe I'm just being a little too picky on that.
Tracking on the DEC is pretty actually pretty good on my mount. Maybe the PHD2 backlash estimate is not quite accurate like some people say on these mounts.
I recently change the TVC from 0 to 10 and that seems to help.

I see the solution for you was the Bellevue washer fix, I take it you had a large 76 second error.
Was it just the washer, or did you switch out different bearings also.
What did that fix take it down to, is it noticeable in guiding or in the PHD2 log viewer?

I'm pretty sure I have the worms meshed satisfactory, it's just that 76 second thing.
Here is a picture,? I hope it shows, of the significant errors from PECPrep.
Thanks for the advice, all help welcomed!

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On Sun, Jun 20, 2021 at 07:26 PM, Brian Valente wrote:

>>> I did start a ticket with support but never got a reply back.

?

?

David we have no record of a support ticket from you (we have a ticketing system too).

?

please make sure you email techsupport at losmandy dot com

?

Email sent June 3rd

?

On Sun, Jun 20, 2021 at 2:22 PM David Malanick <malanick@...> wrote:

Thanks for all the help so far. I went out Saturday night and tried Pempro. Really less intimidating than I thought. Was actually hoping to train a full seven worm cycles, however the random clouds moving across the sky really did not help at all.
Hopefully I can try Pempro again and get some good PEC runs Monday night.
I really appreciate the help on the 76 second error, however the mount is brand-new and under warranty and I really don't want to start tearing it apart yet.
On a night I had really excellent seeing, shooting 30 second subs, I could really tell where the 76 second error showed up. It was like lucky imaging, couple good subs couple bad subs, throwing out about 30% to 40% of subs.
Tried 60, 120 and 300 second subs, that little RA jump really adds up, unacceptable imaging.
If anyone with spring-loaded worms could give a shout out on how they got their final setting tuned in, please let me know.
I'm interested in getting that 1400 to 2500ms backlash toned down a bit. Doesn't affect guiding that bad, just annoying that other people can get it so low.
Wondering how to adjust that back off screw next to the spring. If that is what is needed.
Hope hope the weather will be clear enough soon that I can do another proper PHD2 long guided and unguided run for data.
I seem to have the worms adjusted a lot better than they came on delivery, probably that bumpy FedEx truck and that dandy driver that tried carrying four boxes in one trip and joked about "Looks like they might not make it all to the front porch without falling off the hand truck" when I took delivery.

Has anyone ever gotten an official fix or statement about the 76 second error.
I did start a ticket with support but never got a reply back.
$4000+ is a lot of money to spend if I have to do a do-it-yourself repair and hope that cures it.
Starting to wonder if I'll have to send the mount back to have new bearings and the worms "properly and correctly" adjusted.
Maybe it's just a glitch when the mount was assembled, something out of alignment or too tight or loose.

Thank you,
David Malanick

?

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Brian?

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Brian Valente

portfolio

David,

Sorry to hear about your continued issues. I am sure you want to get the mount operational ASAP. As per the other replies, the 76 seconds error is always due to the bearings and the way they are loaded. If you review the Losmandy videos on worm adjustments. you will see about the need to compress the right block towards the left by squeezing together before tightening the worm block screws. This action might solve your problem and the error could be reduced or go away (as per Henk and Chip).

Potentially the bearings could be mis-inserted or misaligned as they sit inside the blocks and the ball bearings are not riding inside the races at the right angle. You might ask for new bearings and blocks to rule out that possibility. Then there is what you may want to try on your own or have the factory redo. But that is between you and Losmandy on what they cover or recommend.?

Good luck,

John

Well now this screenshot is too cropped, so I have no idea what is the amplitude of your errors.
I don't remember what was my before vs after 76s error.? Except that the mod cut it down to a third or less.? The next biggest problem is 32 s from the gearbox.
The temporary software fix for your RA periodic error is to set the guiding exposure time to 1 s or less.? Do not set it higher because the the mount will not respond fast enough to cancel out the periodic error.
There is a small amount of DEC backlash due to the two big aluminum gears that offset the motor.? That alone is worth about 1+ second.? My post also explains this error and how to test for it.? Go ahead and increase the TVC value until something bad happens.

Here is the results I got with PEMPro.? I really like this program!? Not as overwhelming as I thought. Will have to buy it if I keep the mount.
7 worm Cycles but the results are all over the place. I think the 76 second error is really throwing it off.
Had to crop so it would not be so small.? Hopefully you get the picture of what's happening to me.
Any Ideas?? The suggested curve looks like it would not do much.
There was a suggestion I should use PHD2 PPEC set with a worm cycle of 76 seconds instead of the actual 239.

David,

You may want to post your PemPro file for analysis help. Go to Documents > CCDWare > PEMProV3 > file.ppc. Your screen shots are not looking healthy.?

Regards,

John

Here are the Pempro files

Hi David,

Took your PEMPro data and ran it through on my laptop. I just wanted to see what kind of value range you were seeing in the Y axis, and the drift up and down is not that bad. I would say your polar alignment and seeing conditions were decent. PE of +4.6/-2.5 is fairly tight, but the RMS of 3.25 makes the data a bit rough. Then I am getting a correction curve of 7.12 peak to peak with RMS 2.4. I would probably be satisfied with this curve myself and would use it to program the mount. If you have already have done this and are using PE checked, your guiding results should have changed a bit.

But the Frequency Spectrum is showing your 76 error is larger than the PE as you already presented. Just to illustrate, my last PEMPro run that I did is below. Note the largest error is from the worm period. But since your mount has spring loaded worms and mine does not, a curve from someone who has one like yours might be a better base for comparison. Maybe someone will jump in here with one of their curves.

If you program your mount with the curve generated, you'll compensate for the PE but the 76 second error will remain. This error probably won't be fixed by anything but a mechanical adjustment to the mount. If this error is affecting your photos, some physical action would be needed; PEMPro or PHD2 won't remedy as far as I know. Feedback from HGM as to what they recommend under your warrantee situation will be a big part of your solution.

Hope you find a positive outcome.

Regards,?

John