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Equipment Discussions >> Mounts

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deepskyguy
member


Reged: 12/16/09

Re: CGEM -- first impressions new [Re: jrbarnett]
      #4564402 - 05/05/11 11:19 PM

One other question regarding the clutches. I always leave my mount together and carry it out in the back yard. When not in use, I leave it with the clutches disengaged. What would happen if the clutches were engaged and the mount got bumped or someone moved either the RA or DEC? Would that damage the gears?

Thanks,
DSG


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: CGEM -- first impressions new [Re: deepskyguy]
      #4564474 - 05/06/11 12:10 AM

Quote:

One other question regarding the clutches. I always leave my mount together and carry it out in the back yard. When not in use, I leave it with the clutches disengaged. What would happen if the clutches were engaged and the mount got bumped or someone moved either the RA or DEC? Would that damage the gears?

Thanks,
DSG




How a mount will do with the clutches engaged varies with the mount to some extent. I worry less about an Atlas being bumped with the clutches engaged than I do a CGEM because the Atlas has only 3 large-toothed gears between the motor and the worm whereas the CGEM has about 8 gears between the motor and the worm. However, realistically, the greatest danger is to the worm and ring gears and the clutches would have to be very tight to not slip at all which is not very likely. Overall, there is probably not much to worry about with the CGEM and Atlas mounts and I have seen them shipped with the clutches both engaged and disengaged without damage. I think Celestron recommends shipping with the clutches disengaged but the mount is much more difficult to carry or even get in and out of the box with the clutches disengaged. I usually have to engage the clutches to place the mount in the box or take it out and then release them after it is in the box.

In a mount that has spring loaded worm gears the risk of doing damage to the worm wheels with the cluches engaged may be greater because, rather than the gears being locked together and the clutches slipping, the worm gear might slip up and rachet across the top of the worm wheel doing damage to one or both of the gears.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: CGEM -- first impressions new [Re: EFT]
      #4565543 - 05/06/11 02:49 PM

Ed:

You said something interesting:

"...because the Atlas has only 3 large-toothed gears between the motor and the worm whereas the CGEM has about 8 gears between the motor and the worm."

Folks often assume that these are very similar mounts, other than cosmetics and motor type. It sounds like that may not be wholly accurate. Any idea why Celestron would opt for so many more gears in the drive train than Orion/Sky Watcher?

Are there advantages (real or theoretical) to either approach?

Thanks!

- Jim


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: CGEM -- first impressions new [Re: jrbarnett]
      #4565600 - 05/06/11 03:11 PM

Quote:

Ed:

You said something interesting:

"...because the Atlas has only 3 large-toothed gears between the motor and the worm whereas the CGEM has about 8 gears between the motor and the worm."

Folks often assume that these are very similar mounts, other than cosmetics and motor type. It sounds like that may not be wholly accurate. Any idea why Celestron would opt for so many more gears in the drive train than Orion/Sky Watcher?

Are there advantages (real or theoretical) to either approach?

Thanks!

- Jim




The difference between the two mounts is due to the motors used. The Atlas uses stepper motors which require only a motor spur, an idler gear and a worm spur. The CGEM uses servo motors which have a motor gear box which contains 6 gears if I remember correctly, a motor spur and a worm spur.

There are advantages and disadvantages to both types of motor. The servo/encoder combination has a better idea of its position than the stepper motor without an encoder that relies on counting the steps (or microsteps) made. However, the stepper is far more robust and difficult to damage since if the mount gets jammed, the motor just starts to skip, which sounds awful but doesn't cause damage. The servo motor on the hand is far more delicate and if the mount jams the system applies increase power to the motor to overcome the jam which can result in the stripping of gears inside the gearbox.

When it comes down to it, personal preference for the sound and feel of the motors is often what decides the debate. I prefer the sound of servos over steppers but I can't really say that one works better than the other. The greatest difference between these two mounts is the hand controller.


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delgado39
super member
*****

Reged: 11/13/07

Loc: Glen Ellen, California
Re: CGEM -- first impressions new [Re: EFT]
      #4566159 - 05/06/11 08:33 PM

Would like to add that Ed helped me through the problem I experienced with my used CGEM when the DEC axis was binding on a high spot in the gears. Reported earlier in this thread by JRBarnett. Following Ed's worm gear adjustment directions and "taking my time" the issue was resolved; which I'm greatly relieved. After a 2 star - 4 star calibration alignment and using the precise GOTO feature, I was able to GOTO stars with a 5mm eyepiece and have them appear in the FOV. Amazing. Ed's a great resource in understanding CGEMs. My mount which he hypertuned for the original owner is incredibly well balanced.

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bob midiri
Carpal Tunnel
*****

Reged: 06/17/04

Loc: pa 19320
Re: CGEM -- first impressions new [Re: amys]
      #4566754 - 05/07/11 06:26 AM

Amy I received mine last spring. After a few weeks I started getting errors on the HC. Celestron exchanged HC with me and its been a pleasure to use ever since. I love it, and how it handles my C6R. I do a 2 star western alignment with 3 caleb stars in the east, and its goto's are just dead on. Great mount for the money. Bob

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amys
Carpal Tunnel
*****

Reged: 06/12/06

Loc: Groton, CT
Re: CGEM -- first impressions new [Re: bob midiri]
      #4566809 - 05/07/11 07:15 AM

I'm looking forward to having another opportunity to use it. In the meantime, I'll be checking to see if my Celestron CG-5 hand controller is flash upgradable and if so, will probably order the NexSXW board for my Sphinx. Why not take advantage of clearly superior software if I can, right? Especially with my small scopes, knowing that the go-tos are accurate will help me find those really faint fuzzies.

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BCB
Undercover Saboteur
*****

Reged: 11/24/03

Loc: Look over your shoulder
Re: CGEM -- first impressions new [Re: amys]
      #4566824 - 05/07/11 07:34 AM

Quote:

I'm looking forward to having another opportunity to use it. In the meantime, I'll be checking to see if my Celestron CG-5 hand controller is flash upgradable and if so, will probably order the NexSXW board for my Sphinx. Why not take advantage of clearly superior software if I can, right? Especially with my small scopes, knowing that the go-tos are accurate will help me find those really faint fuzzies.




Agreed.. Up here, we need all the help we can get with our light pollution.. I'm a few miles off the 95 corridor and ill tell ya, some nights, the southern skys BURIED in it..


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