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Balanced RA to the east... how much balance?

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#1 Julian Sanz

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Posted 13 April 2021 - 04:46 AM

Hi, I try to balance my lx200 10 "GPS.

Results: in decline, good. be fixed in horizontal and vertical.

The problem is being in the balance of RA. I have an additional weight on the gps arm of + - 3 pounds. When releasing the RA brake, stay as in image no. 3.

I no longer know if I need more weight there, or less weight.
How do I know to be balanced to the east? The arm where the GPS is to be heavier than the other arm? How much more or less weight? This is my question ..

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#2 michael8554

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Posted 13 April 2021 - 06:02 AM

Hard to get RA balanced.

 

Swing to East.

 

Adjust weight on fork to give best balance between S and E

 

Swing to West.

 

Is it still balanced in RA ?

 

Probably not.


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#3 Peterson Engineering

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Posted 14 April 2021 - 10:30 AM

Hi Julian,

 

Good balance is absolutely critical for imaging and even when using a scope visually good balance saves wear on the drives.  Balancing a wedge mounted SCT isn't that complex if one does it by following a simple 1-2-3-4 sequence.

 

First, point the tube horizontal with all piggybacks, accessories and dew shield mounted - but start with no counterweights.  In this initial step you want to lock the RA axis and simply balance the scope front to back with as little weight as possible.  And the first balance adjustment to explore is moving the piggybacks forward or backward.  With all that weight on top you're going to need counterweight on the bottom and the easiest way to achieve full balance is to simply place a weight equivalent to each piggybacked scope exactly 180° from the appropriate scope with the weight center at the same distance from the optical tube as the piggyback scope centerline. These counterweights can now be moved forward and backward to better balance the horizontal tube.

 

(Note that on my 14" LX200GPS the guide scope rings are bolted directly to the optical tube without a rail and and the visual scope uses the same lightweight ScopeStuff mounting rings bolted to a length of lightweight aluminum channel..  And on the bottom I've got 2 rails exactly opposite the piggyback telescopes holding counterweights.  All 4 rails are secured by existing screw patterns in the Meade tube.  Images below:)

 

Second, even with shifting piggyback position the rails won't go very far behind the Az axis and chances are that even adding the afore mentioned counterweights your optical tube is going to be nose heavy.  Think of a seesaw.  Or a balance.  You can balance with a heavy weight close to the fulcrum or a light weight further from the fulcrum.  This is a crucial concept because one wants to use the minimum counterweight.  The solution is to either extend the rail  toward the rear or add an additional on-axis counterweight that won't impact balance when we point the tube up.  In your case, wrapping that pink Velcro weight around the camera optical train is an option.

 

Third, once the scope's balanced horizontally point the tube straight up vertical.  With the AZ axis still locked. release the DEC axis and move your bottom counterweights closer to or away from the optical tube until you achieve balance.  Note that extending the weights more than 10" or so from the tube will result in them hitting the fork.

 

Forth: At this time  you optical tube should be balanced.  Lock the declination and release the azimuth lock to test for balance of the entire telescope including mount.  Normally, a naked fork mounted big Meade will be a little heavy to the west because the dec drive is in the west fork.  Weight can be added to the east fork (as you've done) to achieve final system balance.  Aim for a very slight bias to the east so that as the scope tracks the drive gears will always be fully enganged.

 

The less weight your scope is carrying the better it will track.  Make every effort to minimize weight.  Once you've gone through the 4 steps above you can fine tune if you wish.  Because this is a fork mounted scope it may be impossible to achieve perfect azimuth balance when imaging low to the E or W but you shouldn't be too far out of whack.  

 

Some personal notes. 

 

You're using a Meade slider weight that doesn't extend out from the optical tube.  Even all the way to the rear it's so close to the RA axis that it doesn't help much in horizontal balance and it's so close in to the optical tube that it doesn't help much with the vertical balance. 

 

Dovetail rails typically used to mount accessories are typically relatively heavy weighing a couple of pounds each.  And the All 4 of my mounting rails are simple lightweight aluminum channel or aluminum extrusions.- some I fabricated myself and some purchased from ScopeStuff.  And the bottom cylindrical counterweights are extended out from the OTA on a threaded rod.  Rails can be very heavy and with the lightweight not-quite-as-stiff rail setups I've saved several pounds.  And with the weights extending our away from the tube I've saved several pounds.  Keeping the weight down is critical, and there's no vibration making ultra-rigidity necessary.  Here's on of my imaging setups.  Note the pickle jar cap fine focus on the guidescope.

 

210414piggybacks.jpg

 

 

You may find info on lightweight counterweight and scope mounting on the ScopeStuff webpage.  One example is http://www.scopestuff.com/ss_pigy1.htm  And you should think about on-axis and mount balance counterweights, and example of which are found here:  https://petersonengi...counterweights/

 

210414CW.jpgHi Julian,

 

Good balance is absolutely critical for imaging and even when using a scope visually good balance saves wear on the drives.  Balancing a wedge mounted SCT isn't that complex if one does it by following a simple 1-2-3-4 sequence.

 

First, point the tube horizontal with all piggybacks, accessories and dew shield mounted - but start with no counterweights.  In this initial step you want to lock the RA axis and simply balance the scope front to back with as little weight as possible.  And the first balance adjustment to explore is moving the piggybacks forward or backward.  With all that weight on top you're going to need counterweight on the bottom and the easiest way to achieve full balance is to simply place a weight equivalent to each piggybacked scope exactly 180° from the appropriate scope with the weight center at the same distance from the optical tube as the piggyback scope centerline. These counterweights can now be moved forward and backward to better balance the horizontal tube.

 

(Note that on my 14" LX200GPS the guide scope rings are bolted directly to the optical tube without a rail and and the visual scope uses the same lightweight ScopeStuff mounting rings bolted to a length of lightweight aluminum channel..  And on the bottom I've got 2 rails exactly opposite the piggyback telescopes holding counterweights.  All 4 rails are secured by existing screw patterns in the Meade tube.  Images below:)

 

Second, even with shifting piggyback position the rails won't go very far behind the Az axis and chances are that even adding the afore mentioned counterweights your optical tube is going to be nose heavy.  Think of a seesaw.  Or a balance.  You can balance with a heavy weight close to the fulcrum or a light weight further from the fulcrum.  This is a crucial concept because one wants to use the minimum counterweight.  The solution is to either extend the rail  toward the rear or add an additional on-axis counterweight that won't impact balance when we point the tube up.  In your case, wrapping that pink Velcro weight around the camera optical train is an option.

 

Third, once the scope's balanced horizontally point the tube straight up vertical.  With the AZ axis still locked. release the DEC axis and move your bottom counterweights closer to or away from the optical tube until you achieve balance.  Note that extending the weights more than 10" or so from the tube will result in them hitting the fork.

 

Forth: At this time  you optical tube should be balanced.  Lock the declination and release the azimuth lock to test for balance of the entire telescope including mount.  Normally, a naked fork mounted big Meade will be a little heavy to the west because the dec drive is in the west fork.  Weight can be added to the east fork (as you've done) to achieve final system balance.  Aim for a very slight bias to the east so that as the scope tracks the drive gears will always be fully enganged.

 

The less weight your scope is carrying the better it will track.  Make every effort to minimize weight.  Once you've gone through the 4 steps above you can fine tune if you wish.  Because this is a fork mounted scope it may be impossible to achieve perfect azimuth balance when imaging low to the E or W but you shouldn't be too far out of whack. 

 

Some personal notes.

 

You're using a Meade slider weight that doesn't extend out from the optical tube.  Even all the way to the rear it's so close to the RA axis that it doesn't help much in horizontal balance and it's so close in to the optical tube that it doesn't help much with the vertical balance.

 

Dovetail rails typically used to mount accessories are typically relatively heavy weighing a couple of pounds each.  And the All 4 of my mounting rails are simple lightweight aluminum channel or aluminum extrusions.- some I fabricated myself and some purchased from ScopeStuff.  And the bottom cylindrical counterweights are extended out from the OTA on a threaded rod.  Rails can be very heavy and with the lightweight not-quite-as-stiff rail setups I've saved several pounds.  And with the weights extending our away from the tube I've saved several pounds.  Keeping the weight down is critical, and there's no vibration making ultra-rigidity necessary.  Here's on of my imaging setups.  Note the pickle jar cap fine focus on the guidescope.

 

 

You may find info on lightweight counterweight and scope mounting on the ScopeStuff webpage.  One example is And you should think about on-axis and mount balance counterweights, and example of which are found here:  https://petersonengineering.com/counterweights/

 

Your Meade 10" is the sweet spot in Meade's lineup Julian.  Hope this somewhat lengthy response is helpful.

 

Your Meade 10" is the sweet spot in Meade's lineup Julian.  Hope this somewhat lengthy response is helpful.

 

 

 



#4 Skywatchr

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Posted 27 April 2021 - 09:26 AM

Hi, I try to balance my lx200 10 "GPS.

Results: in decline, good. be fixed in horizontal and vertical.

The problem is being in the balance of RA. I have an additional weight on the gps arm of + - 3 pounds. When releasing the RA brake, stay as in image no. 3.

I no longer know if I need more weight there, or less weight.
How do I know to be balanced to the east? The arm where the GPS is to be heavier than the other arm? How much more or less weight? This is my question ..

Just enough to keep a small "pulling" load on the drivetrain. That can vary slightly but normally only a pound or two is all it takes. The best position for RA loading is near the base and on the base of the fork. Putting a load on the upper fork and/or OTA increases flexing, which induces oscillations.


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#5 Julian Sanz

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Posted 30 April 2021 - 05:57 AM

Just enough to keep a small "pulling" load on the drivetrain. That can vary slightly but normally only a pound or two is all it takes. The best position for RA loading is near the base and on the base of the fork. Putting a load on the upper fork and/or OTA increases flexing, which induces oscillations.

Hi, thank you very much for your answer, your saying "a little" pull "load on the powertrain", well so do I, I have + - 2 pounds on my left arm. Slightly balanced to the east ... and balanced in decline, but when turning the tube towards the west the tendency towards the east is very strong, not being balanced in the west.
That is, if I balance RA in the east, it will not be balanced in the west


Edited by Julian Sanz, 30 April 2021 - 06:00 AM.



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