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Re: No success in building a pointing model


Mar 23, 2017

 


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#58941 Mar 23, 2017

I recently acquired a used G11.�� It has the latest chip in it.�� It is on a permeant pier in an observatory and is carrying a C14. I do notice a fair amount of movement of the weight shaft in the CWD position.�� I actually tried to re position the worm once and got 80% of the movement eliminated but it seems to have come back.

I have run a lot of models and in the course of doing so noticed a pattern.�� First slew from CTD on Cold Start is fairly close to the target star.�� The second and third on the same side of the meridian get progressively farther off and the first star after the meridian flip is way way off.�� Seems the more stars I put into the model the worse the pointing gets.

A second query,�� With this load on the mount would it be better for me to go to an 18 V power supply?�� Currently have a 13.5 V supply.

Thoughts would be appreciated,

Ed



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#58942 Mar 23, 2017

Does it have Gemini 1 or Gemini II ? My guess from your description is Gemini 1.



From: "eafco@... [Losmandy_users]" Losmandy_users@yahoogroups.com>To: "Losmandy users" Losmandy_users@yahoogroups.com>Sent: Thursday, March 23, 2017 7:17:13 AMSubject: [Losmandy_users] No success in building a pointing model

��I recently acquired a used G11.�� It has the latest chip in it.�� It is on a permeant pier in an observatory and is carrying a C14. I do notice a fair amount of movement of the weight shaft in the CWD position.�� I actually tried to re position the worm once and got 80% of the movement eliminated but it seems to have come back.

I have run a lot of models and in the course of doing so noticed a pattern.�� First slew from CTD on Cold Start is fairly close to the target star.�� The second and third on the same side of the meridian get progressively farther off and the first star after the meridian flip is way way off.�� Seems the more stars I put into the model the worse the pointing gets.

A second query,�� With this load on the mount would it be better for me to go to an 18 V power supply?�� Currently have a 13.5 V supply.

Thoughts would be appreciated,

Ed



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#58944 Mar 23, 2017

Hi Ed,

It is great that you got a C14 to operate on your G11 without stalling errors .("lags" messages).. I think you do not need to increase your DC power supply voltage...if its amps current .capacity is high then you have all the power you need (P=current I .x voltage V). .

But I think the high mass on the G11 mount might make your plastic disk clutches slip.

Since I've had the same trouble as you describe from time to time, my guess is that your clutch disks are slipping.. Slight axis movement can kill the pointing model.. We as a group have been discussing clutch trouble from time to time. .

Even so, if you disassemble your axes, which is easy on the G11, you will see the plastic clutch pads.. Two problems affect these. . First, the nice flat surfaces in close proximity have great capillary action to suck in oil from the axis bearing grease..

.Secondly, the plastic can have a low coefficient of friction to the anodized aluminum surfaces, so even when you clean the oils off, the clutches can still slip.

Losmandy has determined that a change in plastic improves the clutch disks and they now ship the newer higher friction clutch disks. That might improve the friction, but still has the capillary action to eventually pull in oils. .



But I've found a great pad material that solves both problems.. Contact me separately if you want some of those clutch pads. .

Alternatively, you can try cleaning off your metal and clutch plastic disks with a degreaser...maybe alcohol would work.. The clutch knobs with handles on them are also a known big benefit. . But it is possible that overtorquing the back shafts could distort the disk surfaces over time (as one website reported having to file his G11 surfaces back flat).. The right clutch material grabs with a low torque. .

The other possible reason your model gets wrecked is if the Gemini gets wrong initial info. Maybe your SRAM battery is low and the data is corrupt?. Or it happened to me when I use the same PC to run my GM8 and G11 ..the Gemini.net system stores the mount info...then sends that to the Gemini unit. It might tell the G11 that it is a GM8! . .I have to (...ask Paul to...) find a way to have Gemini.net ask to select which default file to use...or better...deselect the automatic initialization. (Hate to buy another laptop just for this). .

Good luck,

Michael.



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#58945 Mar 23, 2017

Regarding voltage, i think you are fine in the 12-18v range. I run mine at 15v which I recall was recommended as a good middleground



Brian



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#58946 Mar 23, 2017

It does have Gemini 1, Based on the input I went back and scanned some of chatter on clutches and found it to be good info.

Michael I would be interested in the pad material you referenced.�� I will figure out how to send to a PM.

Ed



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