Hello,?

I just bought a G11 and am working through it's issues. I know every mount has it's quirks, but some of these I didn't expect.

RA axis the polar scope locking collar was very loose. So I snug it up and make sure I can still rotate the scope but that there's no play.?
Then I tighten the RA clutch and discover that the polar scope can no longer be turned. It's pushing hard against it's locking collar. I had noticed that the scope
turned with the locking collar, which I did not expect. but this was something else.? Relaxing the clutch the polar scope frees up.? I remove the polar scope and tighten the clutch
again. This time i look at the polar scope and eventually discover that the silver focus lock collar is hitting against the RA axis shaft. The only solution is that there must be a spacer missing.?

I go ahead and pull apart the RA drive check the internal bearings and clean the clutch plate and surfaces to get rid of slippage. I discover that the two thrust washers are of different thickness. One is 0.10" and the other is 0.03" . I have no idea if this is correct.? ?The seller had given me a small box with some parts.? In there I find 2 thrust bearings and 2 thrust bearing roller assemblies. The thrust bearings measure 0.125". thick.

Can someone tell me what the thrust bearing thickness is supposed to be?? If I change the .030" bearing for the .125" bearing there may be just enough space for the polar scope to seat correctly.?

Thanks in advance..

Michael.

Ken,?

You may want to carefully inspect the threads on the bar, especially towards the end. Make sure there are no nicks or flat spots on the high points on the threads and that they taper into somewhat of a cone section at the very tip. If you see something you can carefully file out any metal debris inside the thread depressions. If it were me, I would probably wire brush the threads on a wire wheel to polish them down very slightly, after correcting the nicks. Start gently so you don't remove too much metal, and recheck fit.

But then you might have have debris inside the female portion you want to brush out, like Michael said. You could try a toothbrush first, then a brass bristle brush or a steel brush if that doesn't work. Then flush out with WD40 or some GumOut JetSpray carburetor cleaner, followed by compressed air, if you have that.

You probably got some dust or sand contamination in there, common for operations in the dark.

Good luck!?

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Thank you for the modified driver.? I will test it out.

On Sat, Jul 24, 2021 at 05:07 PM, <pcboreland@...> wrote:

Regarding TVC value, I think yo are right. I knocked it down from 90 to 70, but even so the min value selected was 20ms all said and done at the end of the session, which is as low PHD2 can go. You can see the Dec oscillating. I'll reduce it further, but at some point you have to go image something,??

I always leave TVC set at 0 when imaging. When I need to calibrate the auto-guider, I set the TVC value that results in about equal calibration in both directions. Then I turn off TVC for the rest of the session.?

Regards,

? ? ?-Paul

Alan,

I have no control over the north step size. 500ms sees to be the smallest you can go. Are you referring to something else?

Regarding TVC value, I think yo are right. I knocked it down from 90 to 70, but even so the min value selected was 20ms all said and done at the end of the session, which is as low PHD2 can go. You can see the Dec oscillating. I'll reduce it further, but at some point you have to go image something,??

Tonight looks like a bust weather-wise.

Peter

All the north bumps are too big

Thank for the reply Michael. Good tip to use a bottle brush to clean out the threads. And I've seen others mention using a strap wrench, so I'll look to get one.

I guess I'm not sure if I should force it back in, as it stops after just two revolutions with much of the threading still outside. I did use the lithium grease, and maybe once I clean it up and ensure no signs of cross threading, I'll use some moderate pressure with a strap wrench to turn it more...maybe I just need to work past a rough spot?

But it is usable now with it just partially screwed in.

You used too much TVC and the overcorrection shows in the guide logs.

Hi All,? ?I'm a new GM8 owner, and new to trying astroimaging.? I ran into a problem that I can't seem to figure out.? A couple of nights ago, when tearing down at the end of the session, the counterweight bar was difficult to remove.? I tried and hoped it'd get easier, but it got harder to where I couldn't unthread it any further by hand.

Following tips here, the next day I used some WD40, let it seep in a while, then was able to unthread using a wrench.? But now the bar only threads in about two revolutions then won't move.? I haven't tried to force it further, as I didn't want to make the matter worse.??

Looking at the bar and insert threading, I can't see any cross threading, but I did see some bits of metal shavings.? I've tried cooling the bar and heating the female side, along with some white lithium grease, but still the same problem.

Has anyone encountered this before or have any ideas on how to resolve it?

Thanks and Clear Skies!

Ken Black

On Fri, Jul 23, 2021 at 01:27 PM, Brian Valente wrote:

Hi Peter

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Can you post your guidelogs for that night? that would be?great, thanks

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On Fri, Jul 23, 2021 at 1:16 PM pcboreland via <pcboreland=[email protected]> wrote:

New bits arrived today. Will change out the Ra thrust bearings a see if reduces the 2600s error shown in the previous posting. These thrust bearings are German sourced from McMaster!

Also, received the 1024 optical encoders from US Digital. I hate to tear down what is already a superbly performing system, but this is all in the interest of science and you guys. Will put back the 25: 1 ratio gearbox in the Dec axis and install the 1024 step encoder. Lets see if we can achieve same high level of guiding precision while preserving slew rates.

Oh my backlash was 40ms last night and Predictive PEC absolutely nailed the 240s error (see attachment) by totally tuning into it (please note earlier post how I reduced the 80S error), and still no PEC.? The attached image is a 400s Ha single frame of the Cave Nebula, 2.4 um/px. Seeing was horrible and transparency was dire due to lingering smoke in the atmosphere - full moon.

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Brian?

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Here is last night PHD2 log.?

Peter

I was able to run the baseline sequence last night, in the attached guide log this is the 55m section. This was on a fresh install of phd and using a new profile created using the new profile wizard. I seem to be getting the same spikes at 120s, 76s, and 60s.?

On Fri, Jul 23, 2021 at 02:25 PM, alan137 wrote:

On Fri, Jul 23, 2021 at 01:16 PM, <pcboreland@...> wrote:

backlash was 40ms

Try TVC=0 for "real" backlash numbers.

Allan,

I measured the backlash with TVC = 0 and PHD2 returned a value of just under 2s. With TVC = 85 (0.14 arc-sec step resolution) , or 21 at 0.57 arc-sec step resolution,? the backlash measured in at 125 ms +/- 45ms. Now my guiding yesterday adaptively set the backlash at around 40ms. I think this is instructive for folks looking to reduce their backlash. TVC clearly work well at the scope level.

Peter

Hi Bill,

The WO 50mm is what I used for awhile before I moved to a larger guide scope. I had to insert one 1.25" eyepiece extension to gain proper backfocus. Even with the threads full out there was not enough distance. Plus if you are too far unthreaded, you may start to jiggle and create flexure between guide scope and main scope.?

PEMPro is worth it in my opinion since you can do tracking analysis and upload a PEC correction curve right to the Gemini unit. With a good curve in place your guiding software should not have to work as hard and should be more accurate. PEMPro also uses your main imaging camera for more detailed star tracking than with your guide scope. You have a 60 day trial period, so really you can do the proper analysis and curve upload without have to buy immediately. Then you can try guiding with and without PEC turned on to see if it makes a difference in total error.?

Regards,

John

On Fri, Jul 23, 2021 at 02:25 PM, alan137 wrote:

On Fri, Jul 23, 2021 at 01:16 PM, <pcboreland@...> wrote:

backlash was 40ms

Try TVC=0 for "real" backlash numbers.

I know what the real backlash is, I already said, I put it at 2s. It's about guiding performance surely:) Now, I just rebuilt the Dec access using the 1024 encoder and the 25:1 gearbox. I can confirm that I can slew at full speed with this encoder. I also changed out the Ra thrust bearings so will be interesting to see if this has any effect on the 2600s error I've got. I reset my worm mesh, and my TVC value is now 70, which is 17.5 in your money.??

Peter

So my first try at calibrating didn't go so well, but it wasn't a mount issue.? I couldn't for the life of me get a good focus with the guide setup that was good enough for guide assistant to be happy.? It's my own fault.? I'm using a WO 50mm guide scope with the Rotolock.? I took the rotolock off and tried to get the camera hard attached with the correct spacers for back focus, while trying to error on the side of leaving a little room on the focus mechanism (dew shield) to fine tune.? I errored in the wrong direction and couldn't get to focus.? It doesn't get? dark enough here to use the equipment until about 10:15 this time of year and I have a real job so I called it quits and went to bed rather than try to play with the adapters on the camera/scope.

I did get an unexpected bonus yesterday.? ?The neighbors had their monster 100' oak tree removed that blocks my southern view.? I can now see the correct part of the sky from my patio.? I like trees, but I'm glad that one is gone!?

I was thinking about purchasing PEMPro.? Is it worth it just to go ahead and buy it and be done with it or do some of the other tools do just as well when I get to that stage of the setup?? $150 seems a bit steep but I've already dropped the money on the G11, plus about $600 in the addons so what's another 150 I guess.

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If the buyer uses PayPal’s Friends & Family but funds it with a credit card, there is still a fee, about the same 3%. ?It is charged directly to the buyer, though, so there’s no calculating to do in order to deliver to the seller a specific amount of money. ?I believe that fee is avoided if there are funds on deposit in the buyer’s PayPal account or the funds come from a bank account. ?But since I don’t sell much, so don’t have money on deposit, and there’s zero chance I’ll give PayPal access to my bank account, the fee is the same either way. ??

On Fri, Jul 23, 2021 at 01:16 PM, <pcboreland@...> wrote:

backlash was 40ms

Try TVC=0 for "real" backlash numbers.

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