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Re: Meridian Flips and NINA
On Thu, Jul 22, 2021 at 08:55 AM, <pcboreland@...> wrote:
The jump occurs when you cross over the 353 degree boundary in Az.So when crossing over 353 deg in Az, RA jumps by 7 hours? Is? that while tracking or when doing a goto? Did you confirm if that happens on the physical hand controller as well as in the driver display? |
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Re: Meridian Flips and NINA
On Thu, Jul 22, 2021 at 08:36 AM, <pcboreland@...> wrote:
I have no model. I always cold start Gemini.? This problem has existed for months with many restarts/resets. During galaxy seasons target always ended up in this part of the sky, this is when I noticed the flip was failing.?I'm not thinking about the flip failing, but the RA coordinate jumping from 2h to 15h after a small move. Flips are performed by Gemini. ASCOM Driver just sends the command to perform one. |
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Re: Meridian Flips and NINA
Try to clear out and reset any model that you may have in Gemini, cold start, or even fully reset Gemini to make sure.
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Regards, ? ? ?-Paul On Thu, Jul 22, 2021 at 07:59 AM, <pcboreland@...> wrote: Paul, |
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Re: New mount guiding calibration
Hi Bill, I'd get as close as I can to that intersection point.? The question is ...where is it best? If you think about possible errors in polar alignment effects: when you are on the meridian, only errors in AZ affect the star tracking.? That's why you only adjust AZ in a drift alignment procedure when you are on the meridian.? So that suggests you should stay close to the Meridian line, and just be (as you said about 20 deg) off in DEC off the equator.? Anyways...some thoughts for you ... Michael On Wed, Jul 21, 2021, 2:53 PM Bill Grogan <bgrogan267@...> wrote: I received a new G11G about 3 weeks ago.? I¡¯ve only had a few clear nights since receiving it so I haven¡¯t done any guide calibration yet, I¡¯ve just used it as it came and it¡¯s done pretty good stock.? Tonight I have a clear night shaping up and want to go ahead and do the calibration and baseline.? I intend on using the method Brian V has posted several times, but I have a problem.? I can¡¯t see the intersection of the meridian and celestial equator.? So, I was wondering if I could be off of that a bit and still get an acceptable baseline and calibration?? I have several ¡®windows¡¯ of sky I can use that are in that direction but not where it should be.? Those closest window I have is about 45min past the meridian at about +5 dec. ?the closest window I have before the meridian is about an hour and a half before the meridian at zero dec.? I can get right on the meridian if I go +20 dec. Are any of these acceptable or should I just continue using it stock until I can get my rig into a clear view of where I should be? |
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On why the clutch knob matters to worm mesh to the ring gear...
Hi all, There is a lot to talk about here, to resolve several "impossible" puzzles, so please bear with me.?? The unsolved puzzles are: 1. Many people note that their worm gear spacing is very sensitive to the clutch knob force at the other end of the driven 1.25 inch shaft.? What could cause this to occur?? 2. The ring gear can sometimes pinch at a particular rotation angle.? This is not affected by the cylindrical needle bearings.? Why does the ring gear pinch? 3. It is assumed that the worm gear a is and the ring gear are at the same perfect level.? Is this assumption a good one or...should you check it? Let me tell you what's going on in these two issues, and what to look for....and some potential solutions.?? _____ My GM8 DEC axis has a ring gear that rotates around the axis center.? The thick aluminum ring gear is supported underneath by a 3-part needle bearing:. the thick bottom race, the flat thrust needle bearing, and the upper thin race. (In a G11 the thinner race would be at the bottom).? Above the ring gear is a flat surface that contacts the clutch disk.?? The key is that: the ring gear center does not ride on a cylindrical needle bearing!? It rotates on the outer surface of a black tube (not magnetic so I guess anodized aluminium).? That center of the aluminum ring gear will need lubricant to reduce friction there.? See the photo 2nd from bottom.?? That ring gear teeth center height comes from the thrust bearing and it's races below the ring gear.? The heights of the worm center and ring gear center are critical....they must be the same level for the worm threads to be at the finest threads of the ring gear teeth.?? As the worm rotates, friction with the ring gear will either tend to push the ring gear down towards the thrust bearing, or upward. Diwnward should be ok...the thrust bearing is solid.?? But if the worm rotates the other direction, the ring gear will be pushed upward off the thrust bearing. Then the ring gear gets "thicker" and can jam.?? The only thing holding the ring gear down is the weight of the scope (if you were at CWD for instance), or the force of the clutch knob if your axis were horizontal.? Worst case would be with counterweights upward and the weight of the scope pulling downward on the clutch pad.? Then there could be a gap allowing the ring gear to get pushed away from the thrust bearing by the worm friction.?? The friction between the worm and ring gear is critical.? If the metal contact point were frictionless, nothing will happen.? But if there is friction...look what happens.? As the worm pushes the ring gear upward, the ring gear teeth curve outward toward the worm, tightening the grip...tightening the friction.? And this will jam the worm.?? This won't happen if the ring gear center? were slightly above the worm center.? Then as the ring gear got moved upward, the worm would loosen it's grip.? But the other direction of worm rotation would then go tight. That's why the ring gear must be centered on the worm gear , and the ring gear must not be allowed to move up or down...so the clutch knob must be tight enough to hold this.? So:? puzzle #1: Your clutch force is important to assure constant worm to ring gear spacing. The ring gear must not be allowed to get pushed upward by friction from the rotating worm gear.? ?That clutch force is the main thing that keeps the ring gear from getting pushed up or down with respect to the worm.? ?Counterweights up is the worst position for this issue Your work to ring gear lube is important. You want the lowest frictional force between these metal contact points.? I am now using CRC Brake and Caliper grease for this worm to ring gear interface.?? You would want there to be lubricant between the ring gear and the metal cylinder it rides on.? That's usually a brass cylinder in G11 and is a black anodized aluminum on my GM8. I have not lubed that area before.? On the GM8 you must remove the thick ring gear to get to that surface.? The cylindrical needle bearings hold the 1.25 inch steel shafts, but they don't hold the axis of the ring gear. The ring gear is a separate component from the 1.25 inch axis.? Those needle bearing must rotate freely.? They can get gummed up.? When you take out the 1.25 inch shaft you can feel these needles for rotational freedom.?? This also explains why the ring gear can pinch against the worm at a particular rotation angle.? If the ring gear teeth were cut and the ring gear center was off, the ring gear would be "wider" at one point. I thought this is very unlikely, if the ring gear center would be cut first then the teeth cut.? I thought it more likely that there is a slight imperfection in the center cylinder on which the ring gear rides.? If the problem is with that center cylinder, then lapping the worm to the ring gear will not improve this.? If the problem is only with the ring gear centering then polishing/lapping the worm to ring gear would help reduce the high spots. Peter found a gap between his 1.25 inch needle bearings and his 1.25 inch steel shaft but I found no issue there.? Peter found it easy to add or remove needle bearings in his G11, but on my GM8 I find no way to easily remove or replace the cylindrical? needle bearings.? The top of the upper needle bearing is 2 inches below the ring gear surface. See bottom photo looking down this axis.?? I did find my ring gear could be lifted up and down on its center cylinder, even with the worm in place .? It would move about 1mm or so vertically.? I then replaced the upper thrust needle bearing, as Peter did, with a new one (for my GM8 that was a McMaster-Carr INA brand box marked TC2435/0-5-HLA.). That raised my ring gear slightly and the ring gear seems better centered.? It can be lifted slightly...less than 1 mm.? (It would jam is there is no force holding the ring gear down...friction lifted up the ring gear and jams it to the worm gear.) So I think the assumption that every mounts ring gear and worm gear are at the same height .. now has some counter examples.? I suggest that you check it. Here is how Peter determined his corre t worm level: ?Peter removed his worm drive and removed his worm.? He then pressed the worm into the ring gear center...so the sharp edges of the worm are at the sharp center threads if the ring gear.? He then used feeler gauges to measure the height of the thick round part of the worm...there the threads end...to the base where the worm blocks mount.? He found his worm center slightly too high (he measured 0.001 inch too high for the worm).? He solved his issue by buying a new thrust bearing and that new one was slightly thicker than the original...raised up his ring gear and got a closer mesh to his worm. If your worm is not high enough, then as Mark Crossley reported, you can shim under the worm block to get a better mesh.? Here are some photos... Best, Michael |
Paul Kanevsky
Michael Herman