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Old 12-08-2019, 05:00 AM
RussellH
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Telescope balancing questions

So looks like my software and cabling all seems to work although I haven’t hooked up my DSLR yet). I’m almost ready to finally go start taking photos with my new telescope.

Question on balancing. I can get the axes balanced when the scope is horizontal no problem, but when vertical (i.e. pointing at SCP), with all the lopsided weight hanging off the focusser, there is a tendancy for it to swing about 15-30 degrees eastward before coming to rest. No trouble stopping at any spot going westward until it’s at a similar position pointing down.

So the youtube videos I’ve watched on balancing, which say you can put the scope in any position and have it stay there, do not show this with a small scope with significant off-centre accessories. I assume this is why I am seeing this movement. The off-centre weight which is a significant fraction of the scope weight (maybe 10%) is moving the centre of gravity out of alignment with the mount in the vertical positions. Does that sound about right?

I have the tube turned to the eyepiece position is at a comfortable vieiwing angle when checking SCP. I could turn the tube so that the eyepiece position is over the top of the mount in this position, thereby remove some of the off-centre weighting, which may help, but would make visual harder for polar alignment.

Is this something to be concerned about? Should I turn the tube to balance better vertically, or is this small difference within tolerance of “balanced”?

Thanks. Russell.
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Old 12-08-2019, 05:52 AM
Startrek (Martin)
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Russell
Set up your mount in this order
1/ level tripod
2/ tripod front leg centre axis facing True south
4/ install mount
5/ Set home position on mount
6/ Balance mount

Here’s procedure 5 and 6 below

How to set Home Position on your Telescope Mount

1/ Level your tripod pointing to the SCP
2/ Install the mount head and ensure the counterweight shaft is pointing down towards the south tripod leg
3/ Set you Altitude on the mount using the altitude adjusting bolts to the latitude of your current location
4/ Ensure the Azimuth bolts are equally spaced each side of the mount and tighten ( finger tight only )
5/ Do not install the counterweights yet
6/ Stand behind the mount looking south , release the RA clutch and rotate the mount anti clockwise until the counterweight shaft is level . Use a bubble float level to check and then lock the RA clutch
7/ Release the RA clock ring and rotate it anticlockwise until the pointer reaches 6.00 (18.00) don’t tighten up yet
8/ Unlock the RA clutch and rotate the RA axis back to the home position and lick it when the pointer reaches 12.00. Lock the RA clutch
9/ Unlock the Dec clutch and rotate the Dec axis until the saddle is exactly level .Check with a bubble float level then lock the Dec clutch
10/ Release the Dec clock ring and rotate it until it lines up with the pointer at 90 deg. Don’t tighten up yet
11/ Unlock the Dec clutch and rotate it anti clockwise until “0” on the Dec lock ring lines up with the pointer then lock the Dec clutch
12/ The Mount should be now in the “Home Position”
13/ Rotate both RA and Dec clock rings so the pointer lines up with “0” and screw down the clock rings
14/ You are now ready to install your counterweights and balance your telescope

Balancing Your Telescope

Ensure telescope is set in the “Home Position” before you balance
Also ensure all equipment and cabling is installed on your telescope and mount ready to observe or image

Start with balancing Dec axis first
Dec Balancing
1/ Release the Dec clutch and rotate the telescope so it is horizontal and parallel to the ground, then carefully see which way it tilts.Telescope should sit level if balanced
2/ Adjust if necessary by locking the Dec clutch, loosen the tube rings and slide the telescope forward or backward as required and retighten tube rings.
3/Check Dec balance again by releasing Dec clutch and rotate telescope to the horizontal position to check if it sits level.
4/ Repeat adjustments until telescope is freely sitting level then return to home position and lock Dec clutch
5/Release the RA clutch and rotate the mount so that the counterbalance shaft is level and parallel to the ground then lock the RA clutch
6/ Unlock the Dec clutch and rotate the telescope so it is level and parallel to the ground then lock the Dec clutch. If you viewed from above you would see the letter “T” formed by the mount and telescope
7/ Now unlock the Dec clutch while holding the telescope and see if it tilts to one side or the other.Lock the Dec clutch and loosen the tube rings and slide the telescope forward or backward as required then retighten tube rings
8/ Repeat adjustments until the telescope is freely sitting level and parallel to the ground and then retighten Dec clutch. Dec is now balanced in horizontal position.
9/ Now release the Dec clutch and rotate the telescope in the vertical position whilst holding it. If it falls one way or the other you must balance in the vertical position by locking the Dec clutch , loosening the tube rings and rotating the telescope clockwise or counterclockwise , tightening the tube rings and then unlocking the Dec clutch until it remains stationary in the vertical position
10/ Repeat adjustments until the telescope sits freely in the vertical position then rotate the telescope to the horizontal position level or parallel to ground. The telescope should now be balanced in Dec at both horizontal and vertical position
Leave the telescope locked in the horizontal position ready for RA balancing

RA Balancing
1/ Unlock the RA clutch whilst holding the telescope to see if the telescope falls down or lifts up
Move the counter balance weights up or down the shaft as required to ensure the telescope is balanced level parallel to the ground. Adjust as required and lock the RA clutch
2/ Now you need to make the telescope slightly “East Heavy” by moving the counterweights down the shaft a bit so the balancing is slightly in favour of the counterweights. Lock the RA clutch
3/ The telescope should now be balanced in Dec and RA so unlock the RA and Dec and return the telescope to the home position and lock both clutches

Cheers
Martin
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  #3  
Old 12-08-2019, 06:13 AM
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The_bluester (Paul)
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I have found a little imbalance to be not entirely critical, particularly in declination where it can help keep the worm meshed. I typically balance mine in Dec so the scope will gently move the objective high regardless of which side of the meridian the mount is pointed. Similar for RA though it is not as critical. When guiding, the Dec axis will reverse direction so the backlash between the gears comes in to play but the worst the RA does is stop, it does not physically move East when guiding, guiding "East" slows or stops the RA motor so the sky catches up with the scope.
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Old 12-08-2019, 09:08 AM
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sil (Steve)
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As a general rule to help others I've always found it best to manually slew to where I intended to image and balance it there. Then go on to alignment, it can seem after alignment everything is out but when imaging everything tracks nicely. Its a quick and dirty balancing method. Typically you also want to periodically check all fasteners on your gear to ensure everything meant to be locked solid IS locked solid as thermal expansion and use can loosen some fasteners and any tiny amount of play in your system will mean balance can/will shift during a session. Also dont forget to balance with the imaging gear in place, cables and all.
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Old 12-08-2019, 09:18 AM
Startrek (Martin)
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I’ve always been advised and checked quite a few sites and all say to balance from your “home position” which is essentially within a whisker of the SCP
I’ve imaged 2 or 3 targets through the course of a night and never had any trouble with Goto or tracking but maybe others have ?
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Old 12-08-2019, 10:28 AM
RussellH
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Thanks for the tips.

Maybe a little tube rotation is in order. Too far though and it’ll mess up my guide scope cabling. Given I have yet to mount my DSLR and coma corrector, it’s going to add even more weight off-centre.
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Old 12-08-2019, 10:49 AM
Startrek (Martin)
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Your telescope and mount must have everything mounted and wired before you balance , otherwise adding items later will put it out
This was mentioned previously by myself and Sil
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Old 12-08-2019, 11:16 AM
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doppler (Rick)
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When imaging with a newt I find that the tube balance is better if you have the focusser pointing down when in home position. If you’re using a laptop for capture this is ok but might be a bit awkward with just a camera without a flip screen.
Rick
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Old 12-08-2019, 11:34 AM
RussellH
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Quote:
Originally Posted by Startrek View Post
Your telescope and mount must have everything mounted and wired before you balance , otherwise adding items later will put it out
This was mentioned previously by myself and Sil
Yes I realise this. It doesn’t matter what is or is not mounted though, if balance is different when the tube is horizontal vs when it is vertical.
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Old 12-08-2019, 11:36 AM
RussellH
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Quote:
Originally Posted by doppler View Post
When imaging with a newt I find that the tube balance is better if you have the focusser pointing down when in home position. If you’re using a laptop for capture this is ok but might be a bit awkward with just a camera without a flip screen.
Rick
Down as in underneath the scope tube? Doesn’t really matter when hooked to the computer I guess, but certain rules out seeming anything without one.
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Old 12-08-2019, 08:03 PM
RussellH
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So I rotated the tube a little, and things seem to be balanced now, thanks for the advice everyone.
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