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Equipment Discussions >> Cats & Casses

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mmalik
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Re: Meade's new LX800... new [Re: rmollise]
      #5021269 - 01/16/12 05:40 PM

My understanding is that counterweights beyond those supplied by default (2 in this case) would be included in calculating the instrument weight carrying capacity of a mount. If that were a true statement of 'mine' and if Meade intended the same, then my calculations above would be correct. Although I am open to an alternate explanation.

Going beyond the topic a bit, there are two types of forces at work when it comes to mounts; torque and deadweight.

Torque would be taken care of as long as an amount of load put on one side of the pivot is balanced with appropriate counterweight (I didn’t say equal counterweight since that can be adjusted by moving the counterweights along the lever or counterweight shaft).

Deadweight on the other hand is a measure of how much weight a mount can carry or can safely carry. Deadweight has implications for bearings and motors in terms of friction and stress, respectively. This may be going too far but is relevant I think, and some food for thought. Breakdown of 'initial' deadweight on LX800 for a 14" f/8 ACF Telescope are as follows:

Counterweight shaft and cap = 18 lbs.
4 counterweights [needed to balance 14" f/8 ACF] (18 lbs. each) = 18x4 = 72 lbs.
StarLock = 6 lbs.
14" f/8 ACF Telescope = ~60 lbs.
Approximate deadweight on LX800 mount = 156+ lbs.

Note: LX800 mount body (55 lbs.) and tripod (35 lbs.) add up to 90 lbs.

Edited by mmalik (01/16/12 11:13 PM)


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rmollise
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Re: Meade's new LX800... new [Re: mmalik]
      #5021296 - 01/16/12 05:56 PM

Meade told you the counterweights were included in the payload spec? But only _some_ counterweights? Who at Meade told you this?

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Jared
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Re: Meade's new LX800... new [Re: mmalik]
      #5021446 - 01/16/12 07:09 PM

That would be a very unusual way to calculate carrying capacity. I have never heard of a company that rated capacity as anything other than instrument capacity.

As far as dead weight goes... Most mounts can support far more than their rated capacity without risk of collapse, but they become unwieldy because they don't damp vibrations well enough to allow accurate focusing, and they can't be pointed precisely because the mount flexes as it is repositioned or as a gust of wind pushes on the scope. As far as torque goes, even a perfectly balanced load will have limits since the motors will need to overcome increased inertia and increased friction in the bearings that comes with greater loads.

The conservative rule of thumb with manufacturers who rate their mounts based on visual capacity is that the photographic capacity is 1/2 of the rated capacity. This stems from the fact that tracking tends to get less smooth when the bearings are loaded near capacity--generally not a concern to visual observers since your eye doesn't integrate exposures over long time periods. Also more critical for an imager is how well the mount can hold the scope steady with a breeze blowing. This is why there is often a discrepancy between rated capacity for visual and photographic. As far as I know, Meade has not stated whether the capacity of the 800 is photographic or visual. I am just making an educated guess based on its physical size and weight.


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mmalik
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Re: Meade's new LX800... new [Re: rmollise]
      #5021892 - 01/16/12 10:55 PM

Rod, you may have misunderstood me; 'I' was suggesting that counterweights beyond those supplied by default (2 in this case) would be included in calculating the instrument weight carrying capacity of a mount; I shouldn't have used quotes (and have removed quotes).

I was my inferring this from Meade’s ‘New Product Showcase’ in December 2011 Sky & Telescope magazine (p. 56). Note: Please read my original post on 1/15. Sorry for any confusion. Regards!

Edited by mmalik (01/17/12 12:07 AM)


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Alph
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Re: Meade's new LX800... new [Re: Jared]
      #5021966 - 01/16/12 11:59 PM

Quote:

That would be a very unusual way to calculate carrying capacity.



Carrying capacity includes telescope and CWs.
Load/payload capacity is just telescope.
A correct way is to specify both payload and carrying capacity and that's what SB do.


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Jared
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Re: Meade's new LX800... new [Re: Alph]
      #5021988 - 01/17/12 12:28 AM

I stand corrected. I believe all other manufacturers (other than SB) specify just load/payload.

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sphelps
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Reged: 07/03/10

Re: Meade's new LX800... new [Re: mmalik]
      #5022034 - 01/17/12 01:22 AM

Well I guess I'll be the guinee pig cause I pre-ordered a 14" LX800. Like one poster said, if it's too heavy, then just put a smaller scope on the mount and use the 14 for another day.
Anyone have any idea on a release day for these? Meade replied to me today and said this:

" We are hoping for first shipments on this new and exciting product in
the next two months."

Best Regards,

John Piper
Manager, E-Commerce
Meade Instruments Corp.

I was hoping for a release by the end of this month or early next month.

Steven


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herrointment
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Re: Meade's new LX800... new [Re: sphelps]
      #5022166 - 01/17/12 05:18 AM

The Ides of March?

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rmollise
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Re: Meade's new LX800... new [Re: sphelps]
      #5022532 - 01/17/12 10:44 AM

Doc Clay told me he thinks "February"...but that is beginning to sound optimistic.

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KevH
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Re: Meade's new LX800... new [Re: herrointment]
      #5022535 - 01/17/12 10:45 AM

According to the information on Meade's website...

LX800

...the 90 pounds is the rating for the instrument load.

Quote directly from the site...

"Constructed of machined stainless steel and aircraft grade 6061-T6 aluminum, the LX800 mount presents a rock-solid platform with precision roller bearings on both axes. Its .68 inch diameter brass worms and 5.8 inch diameter, 225-tooth aluminum gears deliver smooth, precise movement with up to a 90 pound instrument load. Add to this internal cabling and the AutoStar II fully-computerized GoTo system with GPS, with a database of over 144,000 objects. All this sets atop a new ultra-stable tripod."


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mmalik
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Re: Meade's new LX800... new [Re: sphelps]
      #5023926 - 01/18/12 12:00 AM

Steven, carrying capacity figures I put together were more for the better understanding of the numbers than critique; I am quite sure Meade will do a good job with this release, and that could be the reason for the delay. We’ll look forward to your firsthand reviews of 14" LX800!

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sphelps
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Reged: 07/03/10

Re: Meade's new LX800... new [Re: mmalik]
      #5024074 - 01/18/12 02:29 AM

No problem. I'll give a review as soon as I receive my shipment and I'll post photos. The mount, tripod, counterweight shaft, and (3) weights all add up to over 160 lbs so I think its capable of handling a 70 lb instrument. Now 90 lbs may be pushing it but if it snaps off and drops the 14" optical tube to the ground, you all will be the first to know.

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Stew57
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Re: Meade's new LX800... new [Re: herrointment]
      #5024454 - 01/18/12 10:48 AM

Quote:

The Ides of March?




More like April fools.


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tim53
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Re: Meade's new LX800... new [Re: Stew57]
      #5025579 - 01/18/12 08:16 PM

Quote:

Quote:

The Ides of March?




More like April fools.




Some things never change. When I worked at Meade 30 years ago, they always advertised months before they had working models.

-Tim.


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mmalik
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Re: Meade's new LX800... new [Re: tim53]
      #5026144 - 01/19/12 04:18 AM

Following is a comparative analysis of recent 14” telescopes from Meade with 14” LX800. As we know, LX800 ACFs to some extent are reincarnation of RCX which is good I think. Note: This topic has been discussed in this forum from different perspectives; I thought I’ll put some numbers together for side by side comparison and better visualization.

……………………………………RCX400 14"…..…LX800 14"…..………LX200 14"
Optical design………..……ARC…………………ACF……………..……ACF
Clear aperture…….………356mm …….……356mm……..………356mm
Focal length…………………2,845mm…………2,845mm……….…3,556mm
Focal ratio (speed)…..…f/8……………….……f/8……………………f/10
Resolving power…………0.321 arc sec….…0.326 arc sec……0.326 arc sec
Pointing Precision………2-arc min…….……1-arc min…….……1-arc min
Guiding Accuracy…………N/A…………………1-arc sec…….……N/A

Edited by mmalik (01/19/12 10:59 AM)


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rmollise
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Re: Meade's new LX800... new [Re: mmalik]
      #5026364 - 01/19/12 09:07 AM

Nice chart. Only thing I'd say is that there is no such thing as an "ARC," except in the minds of Meade's marketeers, who I assume have since had to go on to other things.

Oh, and given my experience guiding recent Meade forks, "1 arc second" is...shall we say? "Optimistic?"


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jgraham
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Re: Meade's new LX800... new [Re: rmollise]
      #5026383 - 01/19/12 09:22 AM

From what I've seen all of these companies spec the theoretical resolution. Quoting it to 3 places is a bit much, but that's hardly a sin unique to Meade. I do a lot of double star observing and I've found that it's usually pretty accurate, but pushing the edge requires good alignment, thermal stability, and seeing.

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rmollise
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Re: Meade's new LX800... new [Re: jgraham]
      #5026389 - 01/19/12 09:29 AM

Resolution is merely a function of aperture and can be calculated accurately. Which don't mean your scope will be able to deliver that--all the time or at all.

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Martin Lyons
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Re: Meade's new LX800... new [Re: mmalik]
      #5026453 - 01/19/12 10:15 AM

Quote:

Following is a comparative analysis of recent 14” telescopes from Meade with 14” LX800. As we know, LX800 ACFs to some extent are reincarnation of RCX which is good I think. Note: This topic has been discussed in this forum from different perspectives; I thought I’ll put some numbers together for side by side comparison and better visualization.

……………………………………RCX400 14"…..…LX800 14"…..………LX200 14"
Optical design………..……ARC…………………ACF……………..……ACF
Clear aperture…….………356mm …….……356mm……..………305mm
Focal length…………………2,845mm…………2,845mm……….…3,556mm
Focal ratio (speed)…..…f/8……………….……f/8……………………f/10
Resolving power…………0.321 arc sec….…0.326 arc sec……0.326 arc sec
Pointing Precision………2 arc-min…….……1-arc min…….……1-arc min
Guiding Accuracy…………N/A…………………1-arc sec…….……N/A




At least they are giving you a full 14" clear aperture on the newer models

Seems the older ACF version had a 12" clear aperture according to the table (although I coulda sworn my 14" was a real 14", but then, what do I know

Edited by Martin Lyons (01/19/12 10:17 AM)


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DaveJ
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Re: Meade's new LX800... [Re: mmalik]
      #5026476 - 01/19/12 10:25 AM

Quote:

Following is a comparative analysis of recent 14” telescopes from Meade with 14” LX800. As we know, LX800 ACFs to some extent are reincarnation of RCX which is good I think. Note: This topic has been discussed in this forum from different perspectives; I thought I’ll put some numbers together for side by side comparison and better visualization.

……………………………………RCX400 14"…..…LX800 14"…..………LX200 14"
Optical design………..……ARC…………………ACF……………..……ACF
Clear aperture…….………356mm …….……356mm……..………305mm
Focal length…………………2,845mm…………2,845mm……….…3,556mm
Focal ratio (speed)…..…f/8……………….……f/8……………………f/10
Resolving power…………0.321 arc sec….…0.326 arc sec……0.326 arc sec
Pointing Precision………2 arc-min…….……1-arc min…….……1-arc min
Guiding Accuracy…………N/A…………………1-arc sec…….……N/A




Uh, I think you'd better check that "305mm" figure on the "Clear aperture" entry for the LX200 14". 305mm is 12" and the 14" LX200 is 356mm, not 305mm. I have a 12" LX200GPS and our club has a 14". Trust me on this one, they're not the same aperture!


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