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I agree, get the g11

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

Just to be clear this was done inside and I only did 1 sub after meridian flip to ensure the sequence would continue.??

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Jim W
Phoenix, AZ. USA

Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes

On Sun, Jun 20, 2021 at 01:47 PM, Chip Louie wrote:

Marc,

The original idea behind changing gearboxes was to eliminate the stock plastic gearbox uncorrectable periodic errors caused by the choice of internal gear ratios. There is no measurable hence observable advantage to increasing the mechanical advantage of the gearboxes on a properly adjusted mount.?

A properly adjusted Losmandy mount with the classic 2-piece straight drivetrain should never have zero backlash in a warm room or it will bind and lag as the mount acclimates to a colder environment. In Losmandy mounts with the classic drivetrain backlash shrinks the backlash as air temps fall. This is well known but poorly understood and has led to a zillion different people trying to invent or find ways to overcome a "problem" that is largely caused by not understanding how the mount reacts to its environment. To reliably resolve the changing backlash issue for most people the best solution now comes as standard equipment on all new Losmandy mounts namely the OPW Gen II spring loaded worm carriers.? Being spring loaded allows the worms to consistently maintain minimal backlash hot or cold which is just not possible with the classic 2-piece bearing mounts.? ?

If you need to power through lags or tight spots on the worm and worm gear you need to set your backlash correctly for these spots under the conditions which they occur.?
?

--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

I agree with the clearance needed to account for thermal contraction with changes. There are areas on the transmission train that need to give like crumple zones. I'm still not sold on spring loading the worm meshing though. I need more time. . I'll get to that once I have sorted out my couplings between the gearbox and worm shaft.

On Sun, Jun 20, 2021 at 07:07 AM, <pcboreland@...> wrote:

There are a number of reasons to change out the gearbox from Losmandy. I have the original ones with plastic tabs, their modified version and the 25:1 McLennan. I built my observatory early January in subzero conditions using heat plankets to set the concrete pillar etc. Having an observatory has been a game changer for me with not a single imaging night missed this year. In those winter months my rms error was 0.8 down to 0.5 arcsec rms. This was with the stock gearbox and the one piece worm on the Ra and original worm on Dec. Even with these good tracking numbers my RA was always 30% worse than Dec. So room for improvement I feel. When you look at the FFT response the 32s error was quit high at 0.2 arcsec rms or higher. Very low 76s error and the is some 240s as might be expected. The high 32s error in my mind a definite feature of the Losmandy gearbox they use and is ultimately the limiting factor on performance, assume one knocks down the 76s error. PEC does a reasonable job knocking down the 80s and 240s errors for me.

If you go over to the McLennan gearbox, the 32s will go away due to a different internal gearing arrangement. But you may introduce a significant 9.3s error if you do not reamer out the pinion gear accurately enough to fit the 1/8th inch shaft of the high torque motor. This does not get quided out and a noticable sinewave will be seen in the tracking error graph. Further, I was not impressed with the build quality of the 25:1 ratio gearbox in that there was much play in output shaft relative to the bushings, potentially making worse the 80s and 240s error. You may well trade one set of problems for another.

If you are going to the trouble and expense of changing out the gearboxes, the other option might be to use either a 50:1 or 80:1 gearbox. Early indications are there is significant benefit to doing this in terms of significantly lowering the rms racking error. Presently, I have only experience with the 125:1 gearbox, but a PEC indexing limitation seem to preclude using this high a ratio. Moreover, rpm limitations will drastically reduce slew rates. In the past some have worried that reaming out the very small pinion gear to 1/8th inch might be a problem. I did not find this to be the case.?

In conclusion I would defiantly suggest going to the 50:1 gearbox, but the sweet may well be the 80:1 ratio.

Reaming works well. There isn't much material to remove and a reamer will always follow the original bore so it's very easy to do. Here's a couple of pics when I did mine last year. Close up of the motor shaft.

Hi Vishal,

With a few years of experience owning both a G11G and a GM8G IMO the GM811 is not the value you may think it is as there is little difference in cost but that limitation in payload is right on the edge of needing the 60 pound payload of the G11G. I bought the G11 first and the GM8 as a second mount visual only. As tiem went on I updated the 2005 vintage G11 to a full house G11G with all options available and the G11 which was no slouch but inconsistent became a reliably excellent imaging mount with low PE hot or cold and with no need to adjust as was always the case with the Losmandy original classic 2-piece drivetrain. The GM8 is a great workhorse mount and as a matter of fact I use it a lot more than the G11 because I am in a visual observing group which is always so much fun I forget that I'm an imager. I updated to the GM8 to a fully optioned GM8G and it remains a great mount but it is really not a great mount for longer imaging payloads even though it easily handles a heavy 10" LX200 SCT, C11 SCT and heavy bespoke Parallax/AT130 apo and TEC140 apos. Get the G11G for the extra few hundred dollar more, it is not a lot heavier but it is a lot more stable and will carry your 130mm apo for imaging perfectly and leave you room to move up to that big 160mm apo or RASA-11 with confidence that it will carry them for imaging without a mount change. Trust me.?

--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

Running 1.11 NB 101 and just did a meridian flip using my previous posted settings taking 10min subs.? Subs continued after meridian flip - 1 subs.

The meridian flip coding has changed between 1.10 HF3 and 1.11.x and I believe twice in the 1.11.x release.? I am running Gemini ASCOM driver 1.0.82.0.

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Jim W
Phoenix, AZ. USA

Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes

On Sun, Jun 27, 2021 at 09:38 PM, Edward Plumer wrote:

Paul, were you going to post your parameters for us to look over?

Are you asking me or another Paul? :) I've never used NINA, so have no parameters to share, I'm afraid.

Regards,

? ? ?-Paul

Paul, were you going to post your parameters for us to look over?

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Edward

On Sun, Jun 27, 2021 at 07:36 PM, Edward Plumer wrote:

Paul or others more experienced in Gemini-II.? Do you know how Gemini mounts respond to the ASCOM query "CanSetPierSide".? According to Stefan, NINA first checks this property and sets the new pier side if allowed. This is usually what causes a flip. It then issues a goto back to the same target it case this fails or is not supported.

Gemini.NET reports that it supports setting Side of Pier, and will ask Gemini to perform a flip when so requested. Gemini has internal logic that determines if and when a flip is possible.?

Regards,

? ?-Paul

16 plus minutes?? I will give that a try.? Are you saying at one time the flips worked?

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Jim W
Phoenix, AZ. USA

Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes

Before weather socked in, I was doing 10min subs

On Sun, Jun 27, 2021 at 04:36 PM, Edward Plumer wrote:

Paul or others more experienced in Gemini-II.? Do you know how Gemini mounts respond to the ASCOM query "CanSetPierSide".? According to Stefan, NINA first checks this property and sets the new pier side if allowed. This is usually what causes a flip. It then issues a goto back to the same target it case this fails or is not supported.

First I use the nightly build. Second the flip used to work. Third the flip happens, but it stays on the same side of the pier and eventually hits the limit. Forth I have tried to do this during the day and nothing works. My imaging times are typically 400s to 1000s.

Hi all,

I'm in the market for a new mount for both astrophotography and visual use, and I'm strongly considering picking up a GM811G. The largest payload I currently have is a 130mm triplet refractor (fully loaded ~27lbs and 45" total length). On paper, the GM811G should handle the 130mm fine, however I was hoping to get some input from people more experienced with these mounts on whether the?GM811G is suitable or if I should just spend the extra money and go the the G11G instead. Thanks in advance for any advice.

Vishal

Edward - I have been following the discussions here and on Discord.? This does need more investigation and Gemini-II innerworkings need to be explained to the NINA dev team.? ?I haven't been having issues with my setting but I don't image past 90 sec because of light pollution.? I will try to setup some daytime imaging sessions doing 10 minute subs.? There have been meridian flip coding changes in the Nightly Builds and between 1.10 HF3 and 1.11.x so any testing should focus on the current Nightly Build.

Guilherme - Please consider upgrading to 1.11.x.

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Jim W
Phoenix, AZ. USA

Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes

Chatted with Stefan over on NINA Discord and explained about the issue with pausing. He pointed out that even if the mount is paused, the effective Hour Angle of the *target* to which the eventual goto is performed is still progressing and it will cross the WGL, even if the direction the scope is pointing does not. So, I no longer see how this is an explanation for MF failure without other information. Your thoughts Guilherme?

Paul or others more experienced in Gemini-II.? Do you know how Gemini mounts respond to the ASCOM query "CanSetPierSide".? According to Stefan, NINA first checks this property and sets the new pier side if allowed. This is usually what causes a flip. It then issues a goto back to the same target it case this fails or is not supported.



--
Edward

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guilherme, that is a very useful bit of information. I need to bring this up on the NiNA Discord. Re you using v1.11?
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Edward