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David,

Has anyone got a scan of this?

Thanks,
David

Good to know, Michael. The brass worms may wear over time, as they are softer than the ring gears, but at least they won't be corroding as well:).

My original RA brass worm seems to have an slight indentation where it meets the ring, but the threads have been worn smooth which is what we all want. I am wondering how many thousands of hours we can get out of one, before metal loss might be a problem. At least we know we can replace them when the time comes.

Hello David,

You have a pretty big telescope and you must be an astrophotographer considering the specifications. As Brendan said, after adding accessories, you are getting pretty heavy, and might be getting close to the maximum capacity of the G11G. But it should still work out for you.

But if you can afford it, the G11T might be a better choice for you with the larger weight capacity. And with the Titan, you have more room for additional items like a larger guide scope, bigger camera, and any piggyback secondary telescopes too.?

Best Regards,

John

Keith, I think the discussion was regarding time and latitude/longitude settings. These can be set from the driver. Custom site can also be selected from the driver. Either one can be set to update automatically, when the driver connects to the mount.

Regards,

? ? ? -Paul

On Sun, Apr 4, 2021 at 09:00 AM, Davidspain wrote:

Hola, tengo un newton 300mm f/4 y queria preguntar si la G11G lo soportaria adecuadamente, pesa 24 kg el telescopio.?

Hola David, el g11g tiene una capacidad de 27 kg, pero debes tener en cuenta los extras como la cámara, el visor de guía, etc.



Un Newtonion de 300 mm dará mucha flexibilidad diferencial

Sorry....google translate. ;)
--
Brendan

Henk,

The bearings are pretty inexpensive, about $10 (US). Since the 76 second error is related to the bearings, new will be best. Old bearings could have wear spots or may have been slightly warped during original installation or removal. If the block seats were too tight, or changed with temperature (as per Michael's explanation), the outer races could be slightly out of round, or bent. This may cause the ball hang ups, as per the white paper. So the same bearings may retain their deformations, even after you change the seating or springs tensions.

As per Michael's advice, it seems the right bearing is the one to float, to allow Belville washer tension, but also to permit some slight flex along the worm axis. The left one should remain as the solid base. I suppose that seating could be loosened as well to prevent some crushing, but I have not heard much discussion about that. But installation of the left is still critical, being careful to evenly tap into place without pinching, so tap or push slightly around the edges gently to wiggle into place.?

I have followed Michael's instructions, and read the whitepaper and discussions, so I am following the instructions of those experts. Figuring this out on one's own would take a quite a bit of study and research. Good luck.

Regards,

John

Note that as per the Gemini.net documentation, one can't configure site info in the driver:

"Note: It is not possible to configure the preprogrammed sites via the driver; this must be done via the physical Gemini hand box (Gemini-1) and using the Web interface for the Gemini-2 and Gemini-2 Mini."

Keith

Perhaps it's worth asking Roland in the AP forum as to from where his recommendation stems - surely he must have done some experimentation or has seen evidence of this?

Keith

There is actually another option, namely to stack every 10 seconds and use no PEC or autoguiding at all.? That way the errors will never exceed the errors in a 10 second interval.? The technology is available, I know someone who does this with his ATIK.? Perhaps the live stacking of Sharpcap can do this for general cameras.? If not now, some time in the near future.? The computing power should be there already, it is just a matter of time until people start wanting this feature.

Thanks Ian, that's good to know.? I think the inner block was misaligned because I had to make the flex couplers of my stepper fit, and those have some stiffness while the motor and worm were not perfectly aligned also.? Let me see if I can do a better job at that.??

Maybe an autoguider can handle it but I started looking into it because I get over 1" RMS and I expect this mount to do better.?

I added the spring loading because the mount had more backlash than I liked.? Tightening the worm would simply lead to the mount binding up, I could feel it manually.? The ring gear is just not round enough to have zero backlash.? Looking at the first graph (spring loaded configuration), it doesn't look much better than the second but at least it keeps the mount from binding up when slewing.

So I can pick my poison.? I can align the blocks as best as I can, tighten them, abandon the spring loading, allow backlash (hardly a problem for RA when tracking) and put up with the 240 second cycle and the backlash for slewing and plate solving.? Or I can keep the spring loading, improve it so the 75 second cycle is more regular than what we see in graph 1, and put up with the 75 second cycle.? Or I can drill out the holes in the blocks, apply Belleville washers and spring loading.? Let me try the non destructive options first.?

I had an issue (post DST change?) where EKOS thought the mount was pointing a different location than it was.? Doing a cold start and ensuring the latitude, longitude and time were correct sorted it out for me.

Well, had it setup with new calibration using the guide scope. Guiding started, and. Drumroll..... The clouds rolled in. Boo hisss. I'll have to try when it clears up.

Hello Henk, the high precision worm should give a periodic error of about +/-5” so it all looks ok to me (and the period would be 239 seconds). I found misalignment of motor and worm could give extra harmonics (and this would include any bearing misalignment), so I would also check if everything is aligned well. To get lower values you would need to use PEC. Don’t know what focal length you are imaging at but autoguiding should work well with that level of periodic error.

Hi John,? thanks for the advice and the pictures of your bearing fitting in Alan's thread.? I believe the explanation by John Goetz about the 76 second cycle. Just spring loading will not fix it because the bearings are still misaligned.? Both the worm and the crown wheel are uneven so the spring loaded worm must be moving constantly to compensate.? Therefore the bearings must follow so Belleville washers are the solution.

If I widen the holes in the blocks I should be able to reuse the bearings that I have, should I not?? If yes, why did you buy new bearings?

Also, my outer block bearings should realign themselves because mine float and are pressed by a tangential spring.? So I think the inner block needs the Belleville washer not the outer.? Maybe it's best to do both if there is enough space.? Any thoughts?

To make sure what the frequencies are I imported Ekos' .csv file of the 2nd plot into Scilab and ran an optimization over the sum of a linear and 2 sines (8 parameters altogether).? The outcome is? amazingly clear:? One cycle is 75.63 seconds, the other 240.62 seconds.? The amplitudes are 1.66 and 3.61 arc seconds, respectively.? The fit is like this:


So, by relinquishing the spring loaded worms I get stuck with a significant worm cycle of 1 turn per 4 minutes, Earth's rotation.

Wow!? I thought I was provided with a "high precision worm"?

Ok well my DIY spring loading apparently takes care of it.? So my next quest is to fix the 76 second cycle due to the ball bearings in the worm blocks.? Ugh.

Henk,

Just saw your additional post made while I was typing. Seems like you may have two separate occurrences with overlapping periods. So a glitch with both bearings? Wondering if some additional block to block tension may be needed. Or perhaps to much pressure on the worm towards the ring gear is overcoming the axial tension, and you are again riding too much on the outer races. Perhaps starting a bearing purchase may be in order. I bought a pack of 10 the last time round so I would have extras at home to experiment with, or to see if one is better than another.