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Is the Weight Necessary?

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#1 Ouranos

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Posted 12 May 2010 - 08:47 PM

Here is my new (to me) set up. I "deforked" my C8 and put it on an older CG5. Is the weight bar and weight necessary? Both add weight (!) and make the mount much more cumbersome.

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#2 varmint

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Posted 12 May 2010 - 09:27 PM

Are you referring to the counterweight bar and counterweight?

If so I would say yes, those are required to balance your scope to assure it doesn't put undue stress on the motors.

If not, could you point out what weight's you're asking about?

#3 Ouranos

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Posted 12 May 2010 - 09:57 PM

Jim,
Yes, thanks for the clarification. The counterweight bar and counterweight.
Paul

#4 varmint

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Posted 12 May 2010 - 10:09 PM

Paul,

Thanks, yes the counterweights are needed. You want to make sure the scope is balanced in both RA and DEC so you don't put too much stress on the motors, and also will keep the scope from "going outta control" when you move it manually in RA or DEC.

There's a recent post in the Beginner's forum that discusses how to balance I believe. The process is pretty simple and fast.

#5 BlueGrass

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Posted 12 May 2010 - 10:10 PM

Yes, they are necessary. You need to balance your mount in both planes for proper operation and to keep the wear and tear on the gears and motors to minimum.

#6 Starhawk

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Posted 13 May 2010 - 09:24 AM

No- you should be able to scoot the scope forwards and back on its dovetail to balance it around the RA axis. If you have setups with radically different centers of gravity (e.g. visual and astrophotography), consider putting a mark to help align at the two locations in the dark. I use pieces of white label stickers cut to make large pointers- they show up well in the dark against black equipment.

-Rich

#7 Ouranos

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Posted 13 May 2010 - 12:59 PM

Rich, Just want to be sure - you are offering a dissenting vote? No, the weights and weight bar are not necessary? In my mind, the addition of the weight would put strain on the motors. So, having it off would be better. But, I am a novice w/ GEM mounts.

#8 DaveJ

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Posted 13 May 2010 - 01:39 PM

Rich, Just want to be sure - you are offering a dissenting vote? No, the weights and weight bar are not necessary? It is strange, in my mind, the addition of the weight would put strain on the motors. But, I am a novice w/ GEM mounts.


Trust me, the counterweight shaft & weight are most definitely necessary. Rich is talking about sliding the OTA back and forth on the saddle to achieve balance in DEC, the other axis absolutely requires the large counterweight to balance the OTA in RA. I've been using GEMs since 1960. You can't use a GEM without the counterweight, UNLESS the OTA weighs next to nothing and the counterweight shaft happens to balance the mass of that little OTA. A PST comes to mind here.

#9 hudson_yak

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Posted 13 May 2010 - 04:01 PM

Correct, I'm not sure what Rich really meant to say but what he wrote is flat wrong.

If you take the counterweight off what I see in that picture the first time you don't quite tighten the RA clutch enough the scope will spin down and could clobber the tripod with some quite vulnerable components.

Mike

#10 John Carruthers

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Posted 14 May 2010 - 02:06 AM

You could fit a longer bar and use less mass for the weight, but it may induce more vibration. Bar extensions are available.

#11 astrotrf

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Posted 14 May 2010 - 05:10 PM

In my mind, the addition of the weight would put strain on the motors. So, having it off would be better. But, I am a novice w/ GEM mounts.


Just the opposite is true -- the bar and the weight are there to *balance* the weight of the optical tube so the motor is not fighting gravity. It is important to state that you must slide that weight up and down the shaft until it balances (disengage the RA to do this). You should also slide the optical tube up and down the dovetail to balance the weight in that direction (disengage the declination to do this).

When it's well-balanced in both directions, your motor will have little trouble moving the scope around.

#12 TexomaAU.Obs.

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Posted 14 May 2010 - 05:33 PM

Yes, the counterweight is necessary. You don't want too much stress on any worm gear assembly, as the RA gear will wear unevenly or in extreme cases the gear teeth can break off. As to the motor having wear as a result, it may to some degree as the teeth wear down and cause friction... IN THE END- IT'S ALL ABOUT ENTROPY!

#13 Adrian Lopez

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Posted 14 May 2010 - 05:37 PM

It is important to state that you must slide that weight up and down the shaft until it balances (disengage the RA to do this). You should also slide the optical tube up and down the dovetail to balance the weight in that direction (disengage the declination to do this).

Just don't forget to hold the scope while you disengage each axis (to prevent the scope from hitting the tripod legs and getting damaged if it's not well balanced).

#14 Ouranos

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Posted 14 May 2010 - 07:57 PM

Thanks to everyone for their input. Now, to balance the scope.
Paul






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