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

toggle quoted messageShow quoted text

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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.

开云体育

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.

--

Sorry Brian the Attachment did not post...

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

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

Brian,

I'm not quite ready to release actual guide logs at this point. I'm still studying problems and making changes etc. I did post the FFT analysis for the attached session from two nights back, a few post back. You may wish to take a look. It revealed a large 2600s error in Ra which I attributed to the thrust and or needle bearings or some combination. The take away is I've reduced the native 240s error considerably to the point it guides out almost entirely (mostly through changing the coupler and my own spring loaded design). Also, the 80s error from the bearings is substantially reduced. You can see from this image (attached) that the Dec axis is still playing up a bit. I will be going back to the 25:1 ratio gearbox tonight and using 1024 optical encoder. I fear I damaged my 80:1 gearbox due to a misalignment problem I found and written about with regard to the worm and ring gear and the force needed to rotate the worm. This alignment problem was also picked up by Michael Herman who looked? at one of his mounts and found a similar problem. Its stops a true precise mesh from being obtained. I set the initial backlash prior to guiding at 200ms, and in this case it adaptively brought it down to 43ms. Last night is was 40ms, so a good confirmation. But from the Dec graph something old is going on. Once this is sorted I'll release log files.

Peter

Peter,
I lost track of the Dec axis configuration that resulted in the reported 40 msec backlash. Are these the most relevant configuration items:
-no spring load
-homemade one piece worm block
-added a 3rd needle bearing on Dec axis
-replaced the upper thrust bearing with thicker one

Eric

--

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.

1. If you choose send money to a friend there are no fees.? You have to really not trust the person you are buying from to force them to pay a fee, which they then charge you.?

2. If you ship in a Pelican case. Zip tie it and slap a label on it. I'd look carefully at insurance, it can add a lot to shipping and may not be worth it, read the small print...? If shipping to a neighboring state or two, the post office will be the least expensive option, else UPS or Fedex.? Buy the label online not at a store. Don't over package, like thousands of feet of taped bubble wrap, with every nut and screw equally wrapped:((??

I emailed Jeff this morning and he is not interested in splitting the mount sale between two people, neither is he even reading this thread he started. Seriously..........................................

Peter

On Fri, Jul 23, 2021 at 08:57 AM, Edward Plumer wrote:

Fascinating!? From this video, I am also hard pressed to see how this is not an issue in the Gemini firmware itself since the discontinuity clearly occurs in the HC. When I get back home to my scope, I will try to reproduce as well.

(1)? I lost track of your configurations ... did you see this on both the released and beta version of Gemini firmware??

(2)? To echo an earlier question, can you confirm this only occurs during a slew operation, not during normal sidereal tracking?

(3)? Are you only seeing this around the Meridian, which John relayed is likely to have trickier math?

(4)? If so, do you have any sense of how close you have to be to the meridian during a slew to see the anomaly?

(5)? I gather from your last comment that this does not happen everywhere along the meridian?

As you continue to document this, it might be good to note your lat/lon, time-of-day, rough RA/DEC, etc before the slews to see if there is any pattern that might be useful to someone who knows the code. Also allow others to reproduce the issue by resetting their clock and location in the HC to match your documented occurances.

In the meantime, as a work-around in your automation it might be good to set BOTH "Pause Before Meridian" and "Minutes after Meridian" in NINA to a minute or two, based on what you report for question #4 above. Leave "Max Minutes after Meridian" to the larger value based on WSL. Use the spreadsheet to get consistent values for the other parameters. This should ensure that NINA is not pushing the slew buttons or grabbing bogus coordinates during the window around the meridian.?

I would like to hear whether those settings sufficiently "hide" the occurrence of the anomaly.

By the way, I uploaded a newer version of the spreadsheet with some added round-off error checks.

Edward,?

This issue I do think does lurks at the route of other issues. I experienced it for my self about 6 months ago during galaxy season, but attributed to a configuration problem on my end. I learned to work around the problem buy imaging up to an hour past the meridian.? ?I reported numerous times that I could not get the meridian flip to work correctly. I now realize that the flip did take place, although thank you for your spread sheet. The scope ended up staying on the west side pointing at the ground. I now know the reason for this which I will explain.

I've set a lot of info over to Rene, but this is what I think is happening:
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