Balancing question

[Adam1234]

I've got 2 questions for you guys.

The first one is regarding balancing.

When the telescope on an eq mount is properly balanced, should it stay put if you released the RA and dec clutches no matter the orientation of the scope, or do you expect some amount of movement?

For example, if I oriented the RA and dec axes so the counter weight bar and the OTA is parallel to the ground, then adjust the counter weight and dove tail so that the set up is balanced in this orientation and doesn't move, is it then an issue if the axes move slightly when placed in another orientation for example the home position?

 

The other question, I've observed  bit of wobble in both the dec and RA axis, and it's quite noticeable when looking through an eyepiece if I nudge the scope slightly. Is a bit of wobble acceptable? And how much wobble is acceptable?

 

Thanks

[carastro]

I must admit I don't normally undo both clutches at the same time.  I suppose theoretically it should be balanced.

If I release the RA clutch and turn the set up horizontal, it should stay horizontal if I let go, if it's not then it is a question of moving the counterweights up or down the bar. 

Normally if I release the Dec clutches the telescope should stay horizontal.   If it doesn't then you need to move stuff up or down in the puck until it does.  This might mean moving the dovetail up or down, or even moving the kit further up the mounting rings.  

Having said all that I sometimes find if I put the telescopes back to Home Position, my finderscope which is to one side, or my Filterwheel can make it slightly turn in one direction as they are lop sided, so i just try to get this as balanced as possible.

HTH

Carole 

Edited January 28, 2020 by carastro

[Adam1234]

Thanks for that Carol, my balance is probably more or less correct then, as it is as you described.

[Louis D]

You also need to be balanced along the tube axis.  Any asymmetry along the tube, such as finder or guide scopes, will cause an imbalance as well and you'll need to add counterweights on the other side of the tube to compensate.  You might be balanced when the tube is horizontal, but aim it at the zenith, and it may tip right on backward if it is top heavy.  I have this issue with my alt-az mounts.

[JamesF]

My Skywatcher mounts seem to have a certain amount of resistance to turning in the first place even if they are slightly out of balance.  I think it might be down to the grease they use and the temperature.

Someone posted a video here relatively recently I think showing their CEM60(?).  The OTA appeared to be balanced on the DEC axis and with the DEC axis in the "home" position the RA axis also appeared to be balanced.  Rotate the DEC axis 90 degrees however, and the RA axis was no longer balanced.  That takes a while to get your noodle around...

James

[Neil H]

Hi I only have basic set up telescope red dot finder I can undo both clutches and telescope does not move but it's only a small 114x700

[TerryMcK]

Mine is a fairly lightweight rig - with the cameras, guide scope and ancilliary equipment on probably weighs 10 pounds or 4.5KG- and I have just tried loosening both clutches at the same time. It doesn't move. When I move it anywhere it stays put in any position so guess it is well balanced.

[Ouroboros]

15 hours ago, JamesF said:

My Skywatcher mounts seem to have a certain amount of resistance to turning in the first place even if they are slightly out of balance.  I think it might be down to the grease they use and the temperature.

Someone posted a video here relatively recently I think showing their CEM60(?).  The OTA appeared to be balanced on the DEC axis and with the DEC axis in the "home" position the RA axis also appeared to be balanced.  Rotate the DEC axis 90 degrees however, and the RA axis was no longer balanced.  That takes a while to get your noodle around...

James

Yes. I have owned two equatorials (SW EQ5 & AZ-EQ6) and both have been sufficiently stiff with the clutches off that they can be considerably out of balance before they start to rotate.  I use a sort of dynamic balancing method. I see which direction the mount  is easier to push and how far it moves before stopping. I shift the weight until that feels the same in both directions. 

[JamesF]

48 minutes ago, Ouroboros said:

Yes. I have owned two equatorials (SW EQ5 & AZ-EQ6) and both have been sufficiently stiff with the clutches off that they can be considerably out of balance before they start to rotate.  I use a sort of dynamic balancing method. I see which direction the mount  is easier to push and how far it moves before stopping. I shift the weight until that feels the same in both directions. 

I think belt conversions lie in my relatively near future, so I may well replace the bearings at the same time and hopefully they'll be smoother after that.

James

[TerryMcK]

I should have mentioned my mount is an HEQ5-Pro with the Rowan belt mod so no grease and moves smoothly - no stiction.

[Guest]

I have an HEQ5 Pro with a 200PDS OTA and I do find that the orientation of the scope does affect the balance slightly. Also there is some stiffness in the system so it does not move even if the scope/mount is slightly out of balance. I do what someone else has mentioned. In this case, starting from the 'not moving state' if I nudge it one one direction it will continue moving if I nudge it in the other it doesn't. So I keep nudging this way and that and adjusting until it seems about the same in both directions. Not very satisfactory but there you go.

The instruction manual  has the RA balanced first then the DEC. Both axes are balanced with the OTA horizontal. But I find the balance is not the quite the same when the OTA is in a more normal viewing position.

Also, when balancning the RA it says set the altitude between 15 and 30 degrees but when balancing the DEC set it between 60 and 75. Which is just daft

This is my first experience with an equatorial mount and I haven't had it very long but it seemed much more 'wobbly' than I expected. 

Edited January 29, 2020 by Guest

[celestron8g8]

On my EQ5 when i balance i do one axes at a time . If i add anything extra i will re balance to make sure it’s good to go . But when all is properly balanced if you release both axes same time you probably will have slight movement especially if it’s top heavy . Having proper balanced makes it easy on the gears while tracking so binding is either none or minimum . Also makes it easy on the motors however I’m sure you already know that . But it’s always good practice to have a good hold on the scope so that when you do release the axes you don’t have any unexpected swing in either axes. As far as wobble what part is wobbling , the OTA  or the mount ? Either way I’d find whats causing the wobble and fix it . IMHO  the only wobble acceptable would be from wind or touching . 

[Xsubmariner]

I balance my NEQ6 to a point whereby both clutches are released and I can slowly move either axis to any normal operating position without affecting the other axis. Then I make the mount very slightly east heavy. I do the same with my Cem Mount.

I have found the main hurdle to achieving an excellent balance is cable drag from the; camera, focuser heaters, signal & power cabling. Especially wher there is no through mount cabling. Patience and trial and error usually triumphs.

 

[Adam1234]

35 minutes ago, celestron8g8 said:

On my EQ5 when i balance i do one axes at a time . If i add anything extra i will re balance to make sure it’s good to go . But when all is properly balanced if you release both axes same time you probably will have slight movement especially if it’s top heavy . Having proper balanced makes it easy on the gears while tracking so binding is either none or minimum . Also makes it easy on the motors however I’m sure you already know that . But it’s always good practice to have a good hold on the scope so that when you do release the axes you don’t have any unexpected swing in either axes. As far as wobble what part is wobbling , the OTA  or the mount ? Either way I’d find whats causing the wobble and fix it . IMHO  the only wobble acceptable would be from wind or touching . 

I do try to spend a bit of time trying to make sure it's balanced in dec and RA, and especially if I add or remove anything, or if I end up having to rotate the OTA when the eyepiece has gone in an awkward position... Next time I'm out I'll have a play around with balancing and check the balance in a few other positions and try to get minimal movement. 

Regarding the wobble, I think it's mostly the RA axis (If i push and pull slightly on the counter weight bar the axis moves slightly), there seems to be very little to none in the dec. It might not even do it on it's own when tracking, and it might not even be enough to warrant concern.  I'll have to do some observations and determine that, but certainly if I nudge the scope or the axis, the star/object will move somewhat in the eyepiece/camera view. 

I will also check to see if there's any wobble come from the mount/dovetail 

[Peter77]

7 hours ago, Ouroboros said:

Yes. I have owned two equatorials (SW EQ5 & AZ-EQ6) and both have been sufficiently stiff with the clutches off that they can be considerably out of balance before they start to rotate.  I use a sort of dynamic balancing method. I see which direction the mount  is easier to push and how far it moves before stopping. I shift the weight until that feels the same in both directions. 

I use this method too. AVX mount, pretty stiff in DEC-axis but a little more fluent in RA-axis.

If shooting, I balance with camera etc on, before aligning etc.

 

 

[celestron8g8]

If you only notice movement in the EP when you touch the rig at all then yes that would be normal just looking in the EP . But if you notice it while repositioning the scope or unlocking the axes then  it’s a concern . 

[Guest]

Just been reading Michael Covington's book Digital SLR Astrophotography and in a section about backlash he says that "Mounts actually track better when they are slightly out of balance". It seems a bit unlikely to me but the reason he says is that with a perfectly balanced mount and scope there might be a tendency for it to 'bounce' back and forth across the blacklash.

[JamesF]

13 minutes ago, woodblock said:

Just been reading Michael Covington's book Digital SLR Astrophotography and in a section about backlash he says that "Mounts actually track better when they are slightly out of balance". It seems a bit unlikely to me but the reason he says is that with a perfectly balanced mount and scope there might be a tendency for it to 'bounce' back and forth across the blacklash.

Yes, it is sometimes recommended to have the RA axis arranged so the worm drive will always be pushing against the combined weight of the kit and counterweights.  If I recall correctly that means that when the scope is on the east side of the mount it should be a small amount "top-heavy" (counterweights not quite as heavy as the OTA end) and when the scope is on the west side of the mount it should be a little counterweight-heavy.

James

[Waldemar]

There are three ways to balance a scope: DEC, RA and radial. All three are important to obtain good balance.

RA and DEC are obvious, radial is along the telescope's axes. Any finderscope, filterwheel or motorized focusser will disturb that balance and needs compensation.
A nice way to do that is to lay the telescope perpendiculair on two upside-down T-profiles and see which direction it roles. Compensate for that by replacing or adding weight on the opposite side, untill the scope stops rolling in whatever position it is on the T-profiles.

The only place that needs no compensation is when the weight (like a camera on a Newt, or a filterwheel on a frac) is in the direction of the CW bar.

 

Edited February 2, 2020 by Waldemar

[Adam1234]

16 hours ago, woodblock said:

Just been reading Michael Covington's book Digital SLR Astrophotography and in a section about backlash he says that "Mounts actually track better when they are slightly out of balance". It seems a bit unlikely to me but the reason he says is that with a perfectly balanced mount and scope there might be a tendency for it to 'bounce' back and forth across the blacklash.

I'm reading that book too! Might try that out.

Edited February 2, 2020 by Adam1234

[Adam1234]

8 hours ago, Waldemar said:

A nice way to do that is to lay the telescope perpendiculair on two upside-down T-profiles and see which direction it roles. 

 

What do you mean by this? Struggling to picture it

[Waldemar]

2 hours ago, Adam1234 said:

What do you mean by this? Struggling to picture it

lay two pieces of wood, or T-profile, or what ever material you can think of of about a meter long on the table and lay your telescope on them in such way that it can roll on the material. You should be able to lay it still in any position. If it moves to a certain position you should change the position of whatever causes the imbalance or put some counterweight on the top side, for the heavy side will be lowest.

[Waldemar]

3 hours ago, Adam1234 said:

I'm reading that book too! Might try that out.

That goes for the RA or DEC axes to get rid of backlash.

It does not solve the problem at hand.

[Adam1234]

18 minutes ago, Waldemar said:

lay two pieces of wood, or T-profile, or what ever material you can think of of about a meter long on the table and lay your telescope on them in such way that it can roll on the material. You should be able to lay it still in any position. If it moves to a certain position you should change the position of whatever causes the imbalance or put some counterweight on the top side, for the heavy side will be lowest.

Ah I think I see what you mean now.