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Equipment Discussions >> Mounts

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A. Viegas
scholastic sledgehammer
*****

Reged: 03/05/12

Loc: New York City/ CT
Re: Celestron VX mount [Re: Stew57]
      #5621368 - 01/13/13 06:11 PM

Quote:

The "integer" gearbox is big news if it can be transferred to the CGEM. There is talk of a motor and control board package upgrade for the CGEM. That would take out the 8/3 error and make PPC something really useful in the CGEM. There is talk that there is a firmware update coming that does away with any DEC cogging issues. It looks like the CGEM and the VX are going in the right direction for Celestron.




Would such an upgrade to the CGEM increase its load capacity and allow it to handle a C14 better?

Al


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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: Celestron VX mount [Re: A. Viegas]
      #5621766 - 01/13/13 09:47 PM

It won't increase the ability of the bearings to carry more load, or the case, gears, and worm. It will give a greater tracking accuracy and enable the PPEC to work.

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Ken Hutchinson
sage
*****

Reged: 04/24/03

Re: Celestron VX mount [Re: zawijava]
      #5621926 - 01/13/13 11:41 PM

Quote:

Any confirmation that there are bearings in the Dec Axis?




Yes of course there are bearings on the DEC axis, all mounts have bearings on both axes. I have no idea what kind of bearings the DEC axis has. I am not going to tear my mount apart and I cannot tell what kind of bearings it has without doing that. I would assume that unless Celestron is advertising whatever kind of DEC bearings you are keen to have as upgrades on this mount then it most likely has whatever DEC bearings (plain?) the previous version had.

I will, however, ask my Celestron contact and perhaps I can get you an answer some time tomorrow.

Ken


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core
Pooh-Bah
*****

Reged: 02/23/08

Loc: Mostly in Norman, OK
Re: Celestron VX mount [Re: cn register 5]
      #5621927 - 01/13/13 11:41 PM

Quote:

I checked mine, the latitude goes to just under zero degrees.





Chris, thanks for the confirmation; hopefully the shipped VX will go down to 0° latitude as in your unit (cwt hitting a tripod leg not withstanding); I'm a little weary as the official specs on Celestron's website states 7°-77°; hopefully there's an official option to go lower.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: core]
      #5621977 - 01/14/13 12:25 AM

I'm also not prepared to tear my AVX apart to find out what type of bearing it has. I don't think it really matters, my experience is that whatever it has it does accurate Dec guiding and that's what matters.

I asked about fitting these motor/gearboxes for the CGEM, I was told "not yet".

The 7 degree latitude limit is because of the tripod, not the mount adjustment range. The counterweights would hit the tripod legs.

Chris


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Celestron VX mount [Re: Ken Hutchinson]
      #5621987 - 01/14/13 12:33 AM

Quote:

Quote:

Any confirmation that there are bearings in the Dec Axis?




Yes of course there are bearings on the DEC axis, all mounts have bearings on both axes. I have no idea what kind of bearings the DEC axis has. I am not going to tear my mount apart and I cannot tell what kind of bearings it has without doing that. I would assume that unless Celestron is advertising whatever kind of DEC bearings you are keen to have as upgrades on this mount then it most likely has whatever DEC bearings (plain?) the previous version had.

I will, however, ask my Celestron contact and perhaps I can get you an answer some time tomorrow.

Ken




Ken,

The CG-5 was a perfect example of a mount that did not have bearings of any kind on the DEC axis. Thus, we cannot assume that the new mount has bearings. In fact, based on the apparent size of the DEC axis housing, I am not going to be surprised if the DEC still does not have bearings. I hoping that I am wrong since that was one of the big design flaws of the CG-5. BTW, the LXD55 did not have bearings on RA or DEC axis but it did have brass bushings which the CG-5 lacks. The CG-4 also does not have bearings.


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Whichwayisnorth
Pooh-Bah
*****

Reged: 07/04/11

Loc: Southern California
Re: Celestron VX mount [Re: EFT]
      #5622005 - 01/14/13 12:56 AM

These look pretty nice. I just put in a pre-order for one and I pre-ordered star sense too. Mount should ship this weekend. No idea when the starsense will ship.

Edited by Whichwayisnorth (01/14/13 10:54 PM)


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zawijava
scholastic sledgehammer
*****

Reged: 10/06/07

Loc: Wells, Maine 04090
Re: Celestron VX mount [Re: EFT]
      #5622321 - 01/14/13 09:30 AM

Thank you Ed, I'm glad you understood my question and gave an enlightened answer! -Tim

Quote:

Quote:

Quote:

Any confirmation that there are bearings in the Dec Axis?




Yes of course there are bearings on the DEC axis, all mounts have bearings on both axes. I have no idea what kind of bearings the DEC axis has. I am not going to tear my mount apart and I cannot tell what kind of bearings it has without doing that. I would assume that unless Celestron is advertising whatever kind of DEC bearings you are keen to have as upgrades on this mount then it most likely has whatever DEC bearings (plain?) the previous version had.

I will, however, ask my Celestron contact and perhaps I can get you an answer some time tomorrow.

Ken




Ken,

The CG-5 was a perfect example of a mount that did not have bearings of any kind on the DEC axis. Thus, we cannot assume that the new mount has bearings. In fact, based on the apparent size of the DEC axis housing, I am not going to be surprised if the DEC still does not have bearings. I hoping that I am wrong since that was one of the big design flaws of the CG-5. BTW, the LXD55 did not have bearings on RA or DEC axis but it did have brass bushings which the CG-5 lacks. The CG-4 also does not have bearings.




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Ken Hutchinson
sage
*****

Reged: 04/24/03

Re: Celestron VX mount [Re: EFT]
      #5622635 - 01/14/13 12:57 PM

Quote:


The CG-5 was a perfect example of a mount that did not have bearings of any kind on the DEC axis.




bearing
n
1. (Engineering / Mechanical Engineering) a support, guide, or locating piece for a rotating or reciprocating mechanical part

I cannot speak for anyone else's mounts but both my ASGT and my AVX have some kind of bearings to support and guide the DEC axis. The DEC axle does not flop around loose inside the DEC housing. What the ASGT and probably the AVX have on the DEC axis are plain bearings. They are still bearings though. Some rather large and powerful steam locomotives used to run on bearings no better. They ran well enough that Timken actually had to commission the construction of a steam locomotive with roller bearings which they then loaned to railroads to convince them to abandon plain bearings. I understood perfectly well what the real question was and I promised to give a specific answer when and if I get one. And I still will. How was that not a thoughtful answer??? Just checked my email and I see a message from Celestron about another matter I asked about earlier in the weekend so hopefully they will work their way down to the bearing question in their inbox soon and I can tell you what kind of bearings the mount uses shortly.

So the weather lady just all but promised us sub-zero (F) weather in Chicago by this time next week. Oh joy! If you want to know know how the AVX handles that, ask me next week. Unless it is cloudy....

Ken


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: Celestron VX mount [Re: Ken Hutchinson]
      #5622706 - 01/14/13 01:37 PM

Well, the CG5 has bearings OF A SORT on the dec axis, just not bearings of the sort used on the RA axis. Which is what we want.

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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: rmollise]
      #5623009 - 01/14/13 04:27 PM

I'm quite puzzled by this belief - almost an article of faith - that a plain bearing doesn't count as a bearing. We are talking about an axle that has a maximum rotation rate of 2/3 rpm. Why do people insist that the bearing must be a ball bearing that can run at 1000 rpm or more?

My tests show that the Dec can be guided to an accuracy of an arcsec or two and I think that that - regardless of the type of bearing - is what matters.

From a look at the mount there seems to me to be room for ball races.

Anyway, I've asked, let's see what comes back.

Chris


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mclewis1
Thread Killer
*****

Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Celestron VX mount [Re: cn register 5]
      #5623052 - 01/14/13 04:47 PM

While a "bearing" can be quite a variety of things most folks don't consider a shaft sitting in a curved area cut into the casting of a mount to be a true bearing. True it can function quite well (as proven by the CG-5 and many other mounts) but it's also susceptible to being damaged through dirt/debris or just long term wear and once that happens there is no recourse.

Add a dissimilar metal sleeve in between and you have a "real" bearing, same as adding a race of ball or roller bearings. Any of these can be replaced and in some cases adjusted to compensate for wear or damage.

When bearings are used it is assumed (but certainly not always the case) that tolerances can be tightened up a bit which in our example could make for a mount with a bit less PE.


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tjugo
scholastic sledgehammer


Reged: 11/06/07

Re: Celestron VX mount [Re: mclewis1]
      #5623094 - 01/14/13 05:17 PM

I own a CG5. The mount tracks well but DEC guiding was a big challenge, when imaging the DEC axis suffered from terrible stiction, it took several guide pulses to start moving and when it started it jumped by 4 arcsec. I had better results disabling DEC guiding.

I sent the mount for a tuning service and after that the stiction problem disappeared. So indeed this simple bearing-less design can work if it properly executed, however that is my main concern. I am sure that the beta tester mounts were carefully assembled and perform average or above average of the 'street' mounts.

As already stated a bearing-less design is more sensitive to manufacturing process, assembly, grease quality/amount, debris etc. For me a bearing-less design is a showstopper, at least for AP.

Cheers,

Jose


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Celestron VX mount [Re: Ken Hutchinson]
      #5623329 - 01/14/13 08:08 PM

Quote:

Quote:


The CG-5 was a perfect example of a mount that did not have bearings of any kind on the DEC axis.




bearing
n
1. (Engineering / Mechanical Engineering) a support, guide, or locating piece for a rotating or reciprocating mechanical part

I cannot speak for anyone else's mounts but both my ASGT and my AVX have some kind of bearings to support and guide the DEC axis. The DEC axle does not flop around loose inside the DEC housing. What the ASGT and probably the AVX have on the DEC axis are plain bearings. They are still bearings though. Some rather large and powerful steam locomotives used to run on bearings no better. They ran well enough that Timken actually had to commission the construction of a steam locomotive with roller bearings which they then loaned to railroads to convince them to abandon plain bearings. I understood perfectly well what the real question was and I promised to give a specific answer when and if I get one. And I still will. How was that not a thoughtful answer??? Just checked my email and I see a message from Celestron about another matter I asked about earlier in the weekend so hopefully they will work their way down to the bearing question in their inbox soon and I can tell you what kind of bearings the mount uses shortly.

So the weather lady just all but promised us sub-zero (F) weather in Chicago by this time next week. Oh joy! If you want to know know how the AVX handles that, ask me next week. Unless it is cloudy....

Ken




Ken,

I would say that the DEC axis on the CG-5 does not really even meet this definition. There are surfaces that bear the load in the axis, but they are cast aluminum on cast aluminum that is machined without even a polish to the surface. While nearly any surface can be described as a bearing where one material moves past another, for the layman, bearings are ball, roller, needle so some other kind of bearing that consists of a round or spherical aparatus that rolls between races. The LXD55 had brass bushings that served as the bearing surfaces and, under right circumstances can be made to as good or better a tollerance than ball bearings (but of course that was not the case with the LXD55). I would take the brass bushings over the cast aluminum to cast aluminum contact surfaces in the CG-5. The DEC of the CG-5 causes me more trouble and takes me more time to get to a point that I consider satisfactory than just about any other mount I work on. While such an arrangement can work, it must be implemented correctly and manufactured with precision, which is simply not the case.

I look forward to hearing (and seeing) what you find.

Ed.


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Ken Hutchinson
sage
*****

Reged: 04/24/03

Re: Celestron VX mount [Re: EFT]
      #5624064 - 01/15/13 09:37 AM

I don't know, I talk to laymen all the time who use the word bearing correctly as a generic term like eyepiece. They understand that if you want a roller bearing then you say roller bearing. They would understand that a humble Kellner is still an eyepiece even if it doesn't have a hundred degree field. So far I have no response 17 from Celestron. Perhaps Chris will have better luck.

In the mean time I will try to remember something a couple of my dogs taught me long ago: keep the palm of your hand flat and stiff while feeding Cloudy Nights....

Ken


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astro_baby
scholastic sledgehammer


Reged: 06/17/08

Loc: United Kingdom
Re: Celestron VX mount [Re: Ken Hutchinson]
      #5624415 - 01/15/13 01:28 PM

Ed, you took the words out my mouth there vis bearings.

Also interesting that the CG5 has no bearings in its DEC. i have one here to strip down but havent started on it. It will be the first CG5 I have taken to bits....deep joy. Its my sisters and in a bit of a mess.

I'd agree vis bearing faces that the precision of the faces in most of this stuff is not terribly high, usually its not a problem because it has some kind of bearing ( ball race or other ) but a unit where theres no interface of any kind doesnt to my mind bode well for smooth running even at the slow speeds and low loading of a telescope mount.

With all that said if the mount does run well without them then thats good news I guess, how do they wear I wonder. With the soft ally in these mounts I would think they must have limited life even at the slow speeds they are running at.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: astro_baby]
      #5624963 - 01/15/13 06:54 PM Attachment (119 downloads)

This is the sort of guide log I get, I'm using PHD with an ATK16 camera and a ST80 scope, this has a scale of about 4.3 arc sec per pixel

This is with PEC on and guided. I've measured the PE and the RMS error with PEC on and no guiding seems to be +- 2.6 arc seconds.

Edited by cn register 5 (01/15/13 06:56 PM)


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dr.who
professor emeritus
*****

Reged: 01/05/12

Re: Celestron VX mount [Re: cn register 5]
      #5625321 - 01/15/13 10:17 PM

If I may... I am curious why someone stated that the Orion pier extension won't work with the new mount...? Looking at the photos I can find on the web don't show to me how the knobs would get in the way or for that matter how the mounting is different on the head... Could someone please explain why it won't work?

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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: dr.who]
      #5625615 - 01/16/13 03:33 AM

It's probably because the way the mount connects to the tripod is slightly different.

If the Orion pier extension is for the CG5 then the main difference is that the post that the Azimuth adjuster push against is further out. It should be fairly easy for the manufacturer to drill and tap a new hole for the adjuster.

Chris


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orlyandico
Post Laureate
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Reged: 08/10/09

Loc: Singapore
Re: Celestron VX mount [Re: cn register 5]
      #5625652 - 01/16/13 05:14 AM

0.9" RMS with guiding? that's better than the spec of the LX850

6" p-p with PEC only is a very good figure, if correct.

The graph shows a persistent DEC error on one side only. Looks like a bit of DEC stiction there..

Replacement motors for the CGEM would interest me far more though... hoping.


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