Re: Meridian Flips and NINA
Clouds and rain are back after a brief window of imaging so no new experiments?
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Edward
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Re: Meridian Flips and NINA
Just the meridian flip trigger in the advanced sequencer and the switch in the sumple sequencer?
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On Sun, Jun 27, 2021 at 11:33 AM, Jim Waters wrote:
Edward - have you used the new Smart meridian Flip yet?? How do you like it?
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Jim W
Phoenix, AZ. USA
Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes
? -- Edward
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
I'm not Alan...but I'll pitch in some ideas...?
240 sec is the worm period of a G11 (and half the worm period of a GM8).? {Actually 239.344 sec}
The term "confounded" is used in statistics to mean when several variables can have the same effect on an outcome...so you can't tell what variable is making the effect.??
The 239 sec worm period is confounded with everything that returns to it's same position at that time: 1. The worm itself...can be bad.? Try exchanging the RA and DEC worms to see which gives the lowest PE...then keep the lower one on RA. 2. The Oldham coupler.? Ideally you want the Oldham coupler input and output shafts to be exactly in the same line.? Watch for the center white plastic part movement during worm driving...if that white plastic part is moving up and down or in and out, you should try to adjust your gearbox location (or inner drive shaft location if you have a tucked motor design)? (you may have to enlarge or slot the mounting ear holes if the older direct drive design) to minimize the movement of that center white part. 3. Transfer gears can wobble if you have a tucked motor system. Don't mesh these too tightly... have no tight point. 4. Inner transfer gear drive shaft can wobble if you have a tucked motor system.?? 5. The gearbox drive shaft final gear also rotates at the same rate as the worm. Try a different gearbox.
As Alan has said, the worm period of all these mounts is very long (239 sec on a G11) and can autoguide out very nicely most of the time.? It is the faster oscillation from a bad gearbox (1/7.5 of the worm period or 32 sec on a G11), or a bad RA worm bearing ball getting pinched (~78-80 sec on a G11) that really challenge autoguiding efforts.
Have fun, Michael
Alan,
Are saying that a piece coupler might be best overall in minimizing co-linear problem of the two shafts and provide an overall lower ?240s error? Do you have any recommendations?
Peter
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Re: Very odd polar align issue
Ok.? Let's see what might be wrong:
1. Are your tripod legs really secure? ? ? ? ?Depending on your tripod, if it has telescoping legs, under heavy weight (depending on your scope and counterweight load), the legs can either slip (very slowly collapse!) or if the legs are not in firm (flagstone) ground, they can slip or shift the ground under them.?
2.? Your AZ is secure because you locked down your bolts.? If you did your PA with those AZ bolts loose, the act of tightening them.afterward can causeyour PA to shift!? ?For that reason, I suggest you add in 3/8 Belleville spring washers like shown in the attached photos.? The Belleville springs will give you adjustable AZ bolt pressure.
3. Further related, the AZ mount axis rotates around a central pivot point.? The pivot on these mounts is a central bolt under the mount center.? That bolt has to be loose so the AZ can pivot.? I add a heavy 3/8 Belleville washer to that to also strengthen the AZ rotation.??
4. It was noted that your ELevation bolts might be so tight that you cannot adjust EL.? Same idea as above: using 3/8 Belleville springs on those bolts gives you adjustable pressure.??
See attached photos ...I make up special bolts and spring packages for these.? ?Contact me if interested.
5. Using stars at the pole is good but approximate.? Better is to do a Drift Align using a star at the meridian and equator after the pole star alignment.? Drift alignment is the ultimate way to perfect your PA before deep sky imaging.? PHD2 has good tools for this.? Look into them...
Best, Michael
Making a new thread here since this is a bit different than the other one - not sure of the etiquette.
After Brian's awesome help, I got setup much better last night with the tripod leg facing north.
Following a suggestion, I tightened down the Alt locks pretty tight since I was virtually aligned there.
Went through SharpCap and got "Excellent" PA. Alt and Az locking bolts very tight, mount roughly level, on concrete
Went to PHD (I had previously calibrated). Gemini was off during PA and I had calibrated then turned Gemini off and back on in CWD position
I asked PHD to slew for a drift align (to get in the correct place for a calibrate)
Did a guide assist. After 3 mins, PHD showed I have a 9 minute PA error. I had not physically touched the mount, just asked it to slew (I did forget to sync the mount but it was pointing in a reasonable place)
Asked the mount to slew back to Polaris and sure enough, Sharpcap is showing a similar error to the guide assistant
I did get a couple of warnings in a previous guide assist
- The same PA error
- A warning about guide scope focus (It's in reasonable focus but is a pain to focus so I have put it off a bit)
- A warning to keep exposure times 1-3 seconds (even though I had it at 2.5)
I am connecting to the mount via wifi and its not working that well - I have a wired setup arriving tomorrow as I am tired of messing with it (this is not a mount issue)
I'm at a bit of a loss that I could get such an error in just the time it takes to slew. Everything seems rigid and tight so I am not yet sure where to start looking for issues honestly
If it was just PHD out of sync with Sharpcap that would be one thing, but clearly something has changed on the slew, because I get a different result in Sharpcap
Unfortunately ran out of time to diagnose
I did get a few "random" slews during the night, where I wanted to go to a target but the mount went to a crazy location. Luckily (thanks gto Brian!) I had put in good mount limits so no harm was done.
Going to have a think today and inspect the mount over the weekend to see if there is anything obviously not set correctly
Any suggestions are definitely welcome
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Re: Very odd polar align issue
Will give this a try. I inspected the mount. Tightened everything and checked the bolts. Mount appears perfect abs rigid and working exactly as it is supposed to.?
My theory is that my initial alignment was off. So I will do it a few times next time. Rotating the mount in different directions with sharpcap
If that doesn¡¯t do it I will do a PHD drift align and see where I am with that.?
Thanks for the suggestion also.?
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Alan,
Are saying that a piece coupler might be best overall in minimizing co-linear problem of the two shafts and provide an overall lower ?240s error? Do you have any recommendations?
Peter
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Yet another DIY spring loaded worm - ultra minimalist approach
I have a quite old G11 (18yrs) with a brass RA and steel DEC worm which I got for $100 w/o weights or controller. With a complete clean/lube and Gemini-II w/new motors- I've used it for about a year now with very good AP results at 1000mm fl considering its age (.5-1" guiding on calm nights with good seeing).
That is with the exception for the need to adjust the seasonal temperature sensitive worm block positions and the nightly pause to add one or two 12oz magnetic weights when going over-the-meridian (with the associated backlash / bouncing).
After reading the latest attempts to solve or mitigate the issues with the legacy worm design w/o the wait or expense of buying the Losmandy upgrades, I decided to play with some ideas. While I do 3D modelling and printing, but don't have a machine shop, I am trying a super minimalist approach.?
I added? ~ 1/2" long, 1/4" wide, 1/16" thick piece of rubber band inside the post hole for the outside RA and DEC worm blocks. The DEC band is centered at 90¡ã off the axis of the worm to push the worm directly toward the ring gear and the RA is centered at 45¡ã to push toward both?the ring gear and back against the worm axis (keeping pressure between the ring gear teeth and the worm). The cushioned blocks are now slightly off snug tight and the other blocks are just snug, which gives the blocks some ability to move without being loose. I will need to keep an eye on them working their way loose, but the mount seems to be behaving at least as good as it was before, with visibly improved DEC backlash.
I will update this thread when I get more data on the mount's guiding behavior. While I don't expect to not need to use the weights, I am hopeful the sensitivity to temperature and over-the-meridian and backlash /bouncing is improved.
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Re: Meridian Flips and NINA
Hi
I'm not sure if it will help but i wanted to share my observations from last night which might help fix the issue for you too. First my setup:?
G811G with Gemini-2 - East Limit (ESL): 99.0 - West Limit (WSL): 99.0 - Goto Limit (WGL): 11.00 - Nudge mount...
NINA HF3 - Minutes after meridian: 2 - Use side of pier - pause before meridian: 0
While testing during the day everything worked fine. I was doing 30 secs exposures to test, and NINA performed the flip just fine. The problem happened at night when my exposures were set to 10 minutes. When NINA finished the last exposure before flip, there were still SIX MINUTES left before Gemini WGL. Since the next exposure would finish after the NINA limit after meridian (6 min plus 2 min), NINA decided to wait for the time to flip, but this is important: NINA TOLD GEMINI TO PAUSE THE TRACKING.
So now NINA is waiting for the time to flip, but Gemini is not tracking?anymore so its WGL will?never be reached. When the time to flip was reached, NINA couldn't do it as Gemini didn't allow?it.
?My solution was to increase NINA limit after the meridian to be bigger than my exposures, This way, the last exposure will always finish *after* Gemini WGL was reached already.?
I did have another problem which is related to my other email about random GOTOs happening. After the flip above, while NINA was recentering the object, the mount went crazy again and moved the DEC axis almost 90 degrees from where the object was (I was imaging at Zenith and it moved the DEC almost parallel to ground pointing North), But this is unrelated to the Flip it seems
Does it make sense? Hope this helps.
Guilherme
On Sun, Jun 27, 2021 at 9:34 AM Jim Waters < jimwaters@...> wrote: Edward - have you used the new Smart meridian Flip yet?? How do you like it?
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Jim W
Phoenix, AZ. USA
Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes
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Re: New G11G Looking for final tweaking advice
Here are the Pempro files
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Re: Meridian Flips and NINA
Edward - have you used the new Smart meridian Flip yet?? How do you like it?
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Jim W
Phoenix, AZ. USA
Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes
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Re: Meridian Flips and NINA
Peter, I would also suggest setting up some dummy targets during the day to watch a number of MF while not trying to sleep. What is NINA actually doing when you expected the flip? For example, if in the middle of repeated AF or centering iterations, it might not be checking whether to flip and get stuck at Gemini WSL. Did you enable that Nudge option that Paul showed us?
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Edward
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Re: Meridian Flips and NINA
What version of NINA are you using, what are all of your settings? Mine are fully described earlier in thread.
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Edward
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
The set screw is supposed to dig into the shaft of whatever it screws into.? If you like, you can file or mill a small flat for it.? It is the bearing that sets the concentricity of the worm, not the set screw.? In theory, the coupler is supposed to take into account that the worm shaft is pushed over on one side of its bore.? OF course, you are supposed to keep jamming the set screw into the same spot, otherwise all bets are off.? If you have a 0.0001" micrometer, you can check what is the actual shaft diameter of the worm where it passes thru the bearing.
The problem is not that of worm run-out, the problem is if the worm and [whatever shaft drives it on the other side of the coupler] are not co-linear.? One piece couplers will not give a periodic error even in this case.? The oldham might - I don't know how much.? Just re-adjust the input shaft, then.
The 240s error is not much to worry about because it is SLOW and will easily guide out.? The 80 / 76 s error is 3x worse, even though it has the same amplitude, it has 3x the slew rate.
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Re: New G11G Looking for final tweaking advice
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
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Eric,
Isolating the cause of these errors is a difficult process I think. Really I need to test different adjustments, configurations, etc during daylight hours. ?I do have a 0.0001" dial indicator, so I'm thinking of drilling an access hole in the worm block to get access to the worm shaft to make proper measures of the wobble in realtime. We are looking at 1/3rd and 1 whole period errors, these would be visible to read on the dial indicator I think. I've made the assumption that the 80s error is either a harmonic of the worm or the bearings. I do not think it is from the gearbox. I have assumed any coupler misalignment contributes to the 240s error, but may be it is part of creating a harmonic of the worm period.
There are other factors at play too, particularly RA mount balance, leading to bearing and worm loading. I'm not sure there has been a realtime study as such.
Peter
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Re: New G11G Looking for final tweaking advice
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.
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Peter,
I believe the 76 and 80 second PE components are caused by different mechanisms.
The 76 second component is the bearing BPFO (that period can be calculated from the bearing specifications), which does not appear to be visible on the FFT plot you posted, but difficult to say on a low resolution image. It should be fairly obvious on a chart in the time domain, as the 76 second component is not in phase with the worm.
With the 25:1 McLennan gearbox on my mount, the last stage has a period of 80 sec, so it is difficult to tell if the 80 sec component comes from the gearbox or between the gearbox and the worm.
Also, my mount came with the one piece worm block and Ruland disk coupling, as per your picture. I checked the coupling runout using a dial indicator and it has a significant jump; one of the disks may be damaged as this type of coupling does not allow much misalignment between the gearbox and the worm. Below is the FFT for my mount:
Eric
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Re: Meridian Flips and NINA
My NINA flip failed again last night. Could someone please post their settings that are currently working for them. I'm totally desperate? I need my sleep. Please show image of both NINA and Gemini setups if able.
Peter
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
With a little digging one quickly realizes that problems with the design of Losmandy's worm block goes back 15 years or more. Their solution is the OPW and more recently to spring load it. I feel they could have done a so much better job in the intervening years. Their dimensional choice for the blocks really limits the choice of available couplers. The use of set screws that dig into the shaft of the gearbox and the worm I find totally unacceptable. If you need to remove the worm one will need to file it to get it to pass through the bearings. The worm end will longer be round and will not line up with the coupler without play, guaranteeing a larger 240s error. I just had to buy a second one in less than 2 months due to this. If you want to use a clamping coupler you only have two choices as far as I can tell. These are both from Ruland. Here is the coupler I'm currently using???It does not do the job I feel as it does not remove any misalignment, Ruland has Oldham style couplers, but nothing that is clamp style under 3/4" O.D. There is the seriously more expensive disc coupler? ?This version has 1/4" I.D. at one end and 4mm at the other. It's $182! If anyone has experience with this part and feels it work better than what I'm presently using please advise.?
This image of the OPW from 2010 seems show show the use of this disc coupler, since replaced by a horrid $20 part with set screws.?
This article talks in detail about the earlier 76s error and the 80s error with the OPW and its couases?
Here is my FFT plot from the other night.?
Right now PEC is not working for me for reasons discussed below. I'm optimistic this can be resolved. With the 125:1 McLennan gearbox there very little gear noise. This is great and what I was hoping for. The 80s (bearings) and the 240s (worm + coupler) are the real problem to be focused on. I'm wondering if the axial load on the bearings causing the 80s error can be reduced with bevel washers on the worm side at both ends? I'm also wondering if the 240s error could be reduced with the use of the $182 disc coupler? Your kind input would be appreciate, and sorry for ranting!
Peter
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Re: Very odd polar align issue
A bit of a long shot, but it could be that your alt lock bolts are too tight.? If there is a lot of tension between the alt adjustment screw and lock bolts, they might stutter/slip slightly when the mount shifts its weight.
Try releasing the tension in the lock bolts after you polar align and re-tightening.? You will need to re-adjust your alt slightly.
Regarding random slews, if you're still having issues there is a 2018 beta firmware update that is supposed to address the problem.? You'll need to check the files section of the Gemini_users group.
/g/Gemini_users/files/Gemini%202%20Beta%20ware
-Dwight
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Edward Plumer
Michael Herman
Greg
David Malanick