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Re: California grease
Bob,
If your mount is only two years old the gearbox lube is probably fine because the gears and lube are all sealed up in a nice closed clean environment that operates at a very low load and speed. The gearboxes can add very little drag to the stepper motors and there is no good way to re-lube them without drilling out the plastic or probably in your case, steel rivets to disassemble them and re-lube. You can check the gearboxes once disassembled by turning the gearbox output shaft by hand, there is always going to be some drag and probably a spot where it wants to slow down a little bit but that additional resistance is unimportant as you are working the gearbox backwards and the stepper does not see this resistance. Remember that the gear box is a 25:1 ratio so as long as there is no gritty feeling while turning you are good to go.? One other thing, I'm assuming your GM8 came equipped with the Losmandy HP worms installed but that you do not have a one piece worm block installed on the RA axis. The reason I say this is that either of the OPW designs improves or resolves at least four of the five drivetrain design issues which significantly affect the tracking error numbers of Losmandy G11 and GM8 mount drivetrains.? #1 Worm bearing alignment #2 Worm bearing preload? #3 Worm mesh adjustability? #4 Alignment of gearbox output shaft axis to worm gear axis #5 Gear mesh adjustment? Hope this helps. Chip |
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Re: testing mount without load
Linda Thomas-Fowler
开云体育Thanks to everyone for your answers. I actually just set the mount on the table and ran it without the CW shaft and everything seemed fine.?Software seemed to connect and control properly. The only odd thing was Sky Safari on an iPad Pro (10.7”). Sky Safari was quite sluggish when connected. Lowering the readout rate to 1 or 2 per second (from the default of 4) improved things but it was surprising. Looks like the software is polling the mount in its main loop which is a bad idea for responsive user interfaces. Even at the lower rate there were periodic UI freezes as it polled the mount. Other than that everything went smoothly. Unless you count the awful weather and cold I got since the mount arrived. I’m now two weeks in and still haven’t been able to get outside. Hopefully by the weekend! typos courtesy of iPad On Dec 13, 2017, at 12:29 PM, chiplouie@... [Losmandy_users] <Losmandy_users@...> wrote:
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Re: testing mount without load
Hi Linda,
My old G11 was a 15 year old mount that had a new Gemini 2-mini w/HT-motors and HP worms on both axes. I had Scott rebuild this old G11 as a fully optioned current spec. G11G - Gemini 2-mini w/HT-motors, new design OPWs, tucked-in motors, RAEXK etc. I also own and love my classic GM8G with HP worms that remains un-updated but will will get the tucked-in motors once there is room in the schedule at the shop. I have not worked with the? GM811G, I've watched all of the various prototypes being developed in Losmandy's shop but I don't know if they are being specified and shipped with the RAEXK installed or if it's simply being offered as an option.? So with that said, if testing with an empty saddle I prefer to?leave the counterweight shaft on the mount because this prevents a worse imbalance than taking the counterweight shaft off. If you do remove the counterweight shaft the saddle side of the head will be much heavier and will rotate surprisingly quickly if a clutch is loose or loosened. If your GM811G has the RA extension kit installed it should not hit any other parts of the mount as long as the saddle is completely empty. Even so, with the counterweight shaft in place the imbalance will favor the CWD position and there will be no surprises if a clutch is let loose as the counterweight shaft will always rotate to CWD. Don't worry about the servomotors, even my very first generation Gemini 1 motors will handle this load no problems, the later high-torque motors will have no issue used this way either.? Chip? |
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Re: testing mount without load
Linda,
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As the shaft weighs over 2 kg, I suggest you remove it also. There should be no problem in running Gemini without a load. David At 21:39 12-12-17, Linda Thomas-Fowler linda@... [Losmandy_users] wrote:
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Re: testing mount without load
You can set the Gemini Tracking rate to Terrestrial mode (not sidereal, lunar, solar,...etc). This stops the RA worm and tells Gemini not to expect any ticks from the optical encoders. As for the counterweight... it is not so heavy as to cause any problem for the mount.? The top dovetail does have some weight to it, so I'd just leave the counterweight shaft in place... with no weights on it. Best, Michael On Tue, Dec 12, 2017 at 12:39 PM, Linda Thomas-Fowler linda@... [Losmandy_users] <Losmandy_users@...> wrote:
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testing mount without load
Linda Thomas-Fowler
I’m working on getting my GM811 set up with software and I had a question about what was the appropriate way to run the mount without any OTA. Should I remove the counterweight shaft or leave the shaft attached but without any counterweights?
If I do’t hook gemini up to the mount it complains about stalls I guess since it’s not getting any signals from the Dec or RA axes. What’s the right way to go about this? Thanks! |
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Re: California grease
Bob,
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With the 492 system, don't forget about the grease in the motor gearbox. That grease can cause a slowdown much more than the grease on the worm. Don ----- Original Message -----
From: "robert@... [Losmandy_users]" <Losmandy_users@...> To: <Losmandy_users@...> Sent: Monday, December 11, 2017 2:36 PM Subject: [Losmandy_users] California grease I have a 2 year old GM-8 and was out Saturday night as the temps got close to freezing. I think the grease in the mount got close to freezing too. The mount started getting real quiet -- not silent, but quiet -- and the 15-second exposure stars started looking a little like comets. It's a 492 system. I have the encoders with the Nexus system and it kept dropping out and saying the telescope was not responding. I thought it was a cold Nexus or iPad, but now I think it was its way of saying the telescope wasn't moving or at least keeping up. Is that expected from the factory grease? The axes were for sure stiffer when I was taking everything down than it was when I put it together earlier in the evening. Not hard, but more firm. |
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Re: California grease
Hi Bob,
If possible you really want to use solvent to wash out the old grease and contaminants, blow out the bearings with plenty of compressed air BUT be ready for a lot of black lube to come out in the airstream as it will stain any fabric it hits and will not be coming out anytime soon. I think there was a molybdenum additive to some greases Losmandy uses/used. Additionally make sure the solvent is cleared and/or evaporated before applying the fresh lube. Do not over do the lube, people treat mount bearings like they are on a trailer rolling down the freeway at 65MPH. If the surfaces are clean all it takes is thin coat on all working surfaces and call it a day. Once reassembled rotate the axes to distribute the grease and you are GTG.? I can't say if the grease is coming with Baggies and flipflops or not but it's awful stuff in my book. Cheers/Chip |
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Re: finderscope bracket
Greg,
I have SharpCap 3.1 polar alignment works very well, actually excellent. I just preferred the PoleMaster's camera sensitivity and software guidance. The PoleMaster's software, to me anyway, seems more intuitive and the PoleMaster having a very sensitive mono camera is an advantage for folks using a typically less sensitive DSLR or OSC (one shot color) as the images used for alignment are live on the screen or nearly so depending on sky background nose.? One other thing, for astronomy club field use you can go from mount to mount and polar align visual observer mounts which is a help for those without polar scopes. That said, SharpCap's alignment routine works very well within the context of the camera limitations.? Chip ?? |
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Re: California grease
Hi Chip!
I've been reading along about the gear mesh vs temp discussion. Interesting. My gears are barely meshed (I really have to adjust things at some point -- just haven't gotten around to messing with it since I bought it), so I'm thinking this is the grease. The temps were close to 60 then to 30F kinda quickly. Those Hollywood types...their grease probably comes with a free pair of Baggies and flip-flops. :) Grey tube SuperLube to the rescue! I guess I'll tighten up stuff then too. Thanks! Bob |
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Re: California grease
Hi Bob,
I have had two issues with changes in air temps and tracking error, lubricant as you mention and worm gear mesh. Whatever lubricant is used by Losmandy seems to get stiffer as it gets colder making the mount tracking error level increase as temps fall. As the grease get hotter it gets thinner and over time separates making a runny mess and over time drying out the lubricant making the mount stiffer over time even when warm. The lube issue is an easy fix, just go online and buy a tub/tube of Synco's food grade pure synthetic SuperLube Multi Purpose Grease with PTFE, NOT the Silicone stuff. SuperLube is a true pure synthetic - this stuff stays put very well in the heat with minimal migration and minimal separation of the base. But more importantly IMO for telescope mount applications - it stays very soft even when you are frozen solid, the coldest I have stayed out is about 20F and the mount was tracking perfectly. As you no doubt have experienced in SoCal we can easily experience 50F-70F swings in air temp in the high desert areas where it is darkest. This stuff works perfectly and if you buy it in a tub it's even reasonably priced. Here is an Amazon link:.? ? The other worm gear mesh issue is mechanical binding as the mount gets colder the clearances shrink significantly causing drag and eventually binding and stalling mount movement. So if you set your worm mesh up to have minimal backlash at the tightest point with the large worm wheel in your nice warm house then go outside and the air temperature drops it will get tighter. The only way to avoid this is to set your worm gear mesh in the cold and let the backlash be larger when hot and not in use. My own experiences has been that the mount will guide and track much better with the worm set slightly loose when cold rather than set up perfectly. In other words some very small backlash is needed or tracking suffers.? Chip ? |
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California grease
I have a 2 year old GM-8 and was out Saturday night as the temps got close to freezing. I think the grease in the mount got close to freezing too. The mount started getting real quiet -- not silent, but quiet -- and the 15-second exposure stars started looking a little like comets. It's a 492 system. I have the encoders with the Nexus system and it kept dropping out and saying the telescope was not responding. I thought it was a cold Nexus or iPad, but now I think it was its way of saying the telescope wasn't moving or at least keeping up. Is that expected from the factory grease? The axes were for sure stiffer when I was taking everything down than it was when I put it together earlier in the evening. Not hard, but more firm. Thanks! Bob |
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Re: Polar Scope
Now that the trees have dropped their leaves I was able to try the polar alignment tool in Sharpcap. Pretty amazing... got a decent alignment in record time and a lot more fun than my old drift alignment approach. One points the scope in the general direction of Polaris -- the tool platesolves where you are pointing, then asks that the scope be rotated in RA roughly 90 degrees, then platesolved again. An arrow on the screen shows which way the aim needs to be shoved and an error circle is displayed. So you move the scope a tad and rerun the second image. A couple of passes through this loop and you are done. I was using a Mallincam USB astronomical camera so it was close to live video. The camera was on my scope rather than the guide scope as I wanted to correct the mount, then adjust the guidescope to point at the same place. Worked for me...?
greg latiak avalon observatory |
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Re: Just purchased GM811GHD
开云体育All of my astro efforts are done at sites several hours drive away. I have used agm and gel cell batts for running computers mount and cameras. A 79 AH agm has worked well except in cold weather for about 2 nights of imaging with guiding. I recently replaced that with a 50 Ah LiFePO4 batt and found I could go 3 nights on the same setup. At about half the weight, my back has thanked me a lot. My wallet on the other hand is still whining?. I plan to swap out 2 gells (32AH) and another 79 AH agm with more LiFePO4s as the existing batts age and the LiFePO4 batt prices drop. Cheers? Loren On Dec 8, 2017, at 11:52, crocco1250 crocco1250@... [Losmandy_users] <Losmandy_users@...> wrote:
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OnStep Goto Conversion
A few GM8/G11s have been converted to stepper operation by members of?/g/onstep. Stepper drivers, basically current amplifiers, have come a long way since the 492 was developed in the early '90s as have microprocessors. Stepper motors are quite quite when operated at high microstepping rates. Current drives can break each step into 128 movements.? These improvements permit a NEMA 11 stepper (?Frame Size (28 x 28mm)?with a 18;1 gear head to drive a G11. The motor and its gear head tuck neatly under the RA worm housing.? ? |
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Re: Just purchased GM811GHD
开云体育Bryan I agree.? Look at the weight of a slave vs li-fe-po4, though.? An sla gives you a good workout lugging it around! Chuck Sent from my Samsung Galaxy Tab?|PRO -------- Original message -------- From: "bryancashion@... [Losmandy_users]" <Losmandy_users@...> Date: 12/08/2017 12:28 PM (GMT-08:00) To: Losmandy_users@... Subject: RE: [Losmandy_users] Re: Just purchased GM811GHD ? At 0.5 A, a 22 Ah battery would be good for 22 hours on the basis that these types of batteries should not be discharged to more than 50% pf their capacity. 22 Ah*50%/0.5A? = 22 hours
I have had good luck with Power-Sonic SLAs (I have 3).? This is a link to their 12V series. ? Bryan Sent from my Samsung Galaxy Tab?|PRO -------- Original message -------- From: "bvalente@... [Losmandy_users]" <Losmandy_users@...> Date: 12/08/2017 11:33 AM (GMT-08:00) To: Losmandy_users@... Subject: [Losmandy_users] Re: Just purchased GM811GHD ? yes, they will definitely work.? Car starter batteries are more designed around offering a maximum amperage to kick over the motor.? for astro that's not important -? instead we want greater battery capacity, hence amp-hours if your losmandy pulls .5a then a 22 amp-hour will last about 11 hours, or pretty much all night long me, I power my losmandy G11T, intel nuc i5 computer, focuser, dew heater, camera, guide camera, and whatever USB junk is connected to my computer. so my amp-hour usage is a lot more. just FYI B ? |
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Re: Just purchased GM811GHD
开云体育Right – what he said ;) ? Thanks ? Brian ? ? Brian Valente Brianvalentephotography.com ? From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Friday, December 8, 2017 12:28 PM To: Losmandy_users@... Subject: RE: [Losmandy_users] Re: Just purchased GM811GHD ? ? At 0.5 A, a 22 Ah battery would be good for 22 hours on the basis that these types of batteries should not be discharged to more than 50% pf their capacity. ? 22 Ah*50%/0.5A? = 22 hours ? I have had good luck with Power-Sonic SLAs (I have 3).? This is a link to their 12V series. ? ? ? Bryan ? ? Sent from my Samsung Galaxy Tab?|PRO
yes, they will definitely work.? ? Car starter batteries are more designed around offering a maximum amperage to kick over the motor.? ? for astro that's not important -? instead we want greater battery capacity, hence amp-hours ? if your losmandy pulls .5a then a 22 amp-hour will last about 11 hours, or pretty much all night long ? ? me, I power my losmandy G11T, intel nuc i5 computer, focuser, dew heater, camera, guide camera, and whatever USB junk is connected to my computer. so my amp-hour usage is a lot more. ? just FYI ? ? B ? |
Michael Herman
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