Newtonian Balancing Question

[multiweb (Marc)]

Hi Guys, I have a scope balancing question. I have a small 5" newtonian. By the time I stick a barlow and a QHY8 in it it's a fair bit of "off axis" weight so really I should have a counterweight inline on the other side of the focuser. What's the common practise out there? Use a tube ring with a threaded rod and a disc weight? Not sure which way to go? Thanks for any pointers.

[rmcpb (Rob)]

You could try a speaker magnet with self adhesive felt on it. Just plonk it on the tube and move it till the tube is balanced.

[multiweb (Marc)]

Originally Posted by rmcpb

You could try a speaker magnet with self adhesive felt on it. Just plonk it on the tube and move it till the tube is balanced.

You lost me there...

[kinetic (Steve)]

Originally Posted by multiweb

Hi Guys, I have a scope balancing question. I have a small 5" newtonian. By the time I stick a barlow and a QHY8 in it it's a fair bit of "off axis" weight so really I should have a counterweight inline on the other side of the focuser. What's the common practise out there? Use a tube ring with a threaded rod and a disc weight? Not sure which way to go? Thanks for any pointers.

I think the obvious answer is that your QHY-8 is simply not suited
for your scope and you should mail it to me as soon as possible.

Failing that, this is what I use on my Newt:
I screwed an aluminium extrusion rail to the bottom end of the OTA
diametrically opposite the finder/focusser.
It has a dovetail triangle hollow within the rail that holds a slightly
smaller triangular 'captured nut'
A smaller piece of aluminium angle attached to this nut is the surface
that I add small G-clamps as counterweights.
They aren't actually G-clamps, but roofing purlin brackets, but they look like
little solid g-clamps...plus they are heavy.
I can add these and also slide the whole carriage they sit on up and down the extrusion.
It works....rough, but does the job...
I will try and take some photos of it...and edit this post.DONE

Steve

[multiweb (Marc)]

Originally Posted by kinetic

I think the obvious answer is that your QHY-8 is simply not suited
for your scope and you should mail it to me as soon as possible.

That is an excellent solution Steve. I like it a lot. Thank you.
PS: I have a better idea: instead of me mailing you the QHY8 what about we make a scope swap? My 5" for your 10"/8"?

[AlexN]

Better idea, you send me your G11, I'll send you my EQ6 + Megrez 102, the 102 will be great with the QHY8 (as it is with mine) and the eq6 is more than enough for the setup.... the G11 will hold my C11 beautifully (and be sexy anodized black) and then everyone is happy (refractors are beautifully easy to balance )

Alex.

[Glenn Dawes]

Providing it is a metal tube, use a torch with a magnetic base on it and slide that up and down to get balance (you might have to wrap the base with a soft cloth to prevent it scratching the tube). Then when you've finished use your 'counter weight' to help you see when you're packing up.

Glenn

[gbeal]

Depends a little to me Marc. In my case (newt, bigger, but similar), I keep the focuser pointed towards the mount, thus keeping the weight as close to the rotation axis as possible. If the focuser and weight (barlow/QHY etc) is in line then there should be no reason to counter-balance it surely.
Gary

[HandyAndy]

Hi,

If you are doing imaging or want to use the telescope manually without locking the RA and DEC all the time you need to balance the tube on 3 axes which means it is dynamically balanced all the time.

I think Sidgwick has diagrams.

You need to balance the OTA and balance weights when the RA is horizontal, and the tube on the 3 axes. It takes a bit of working out to get the tube in 3 orthogonal orientations. You probably need to go round a few times because of adding weights as you go. One is vertical and the other two are horizontal with the tube rotated 90 degrees.

On my old Fullerscopes MK4 mount I had as large diameter knobs made for the RA and DEC clutches so I could finely set the loading so I could manually move the scope and have the motor continue driving afterwards.

Then it is usuall to set it slightly out of balance if motorised so the scope is resting slightly on the gears to reduce any backlash.

If the mount is well greased up that tends to help with damping.

If the OTA is well within the mounts capability then it is easier to get it set so that it is easy to use.

Cheers. Andrew.

[Ian Robinson]

I've been known to hang a little bag with ball sinkers in it , ball sinkes , from the tube to tune the balance if I add a heavy bit of kit to the focusor , keep adding sinkers til the tube is pretty much balanced - and cheap as chips .... everyone has fishing gear and sinkers.

If the tube is balanced , and you know the mass of the added gear , it's easy to calculate how much mass to add on the over side of the centre of balance to get very close to balance again.

mass1 x length1 = balance x length2 , where length1 is the distance from the pivot point (centre of balance) for added mass1 , and balance is the mass required at the hanging point to rebalance the OTA.

[multiweb (Marc)]

Thanks for all the feedback guys. Much appreciated.

Originally Posted by gbeal

Depends a little to me Marc. In my case (newt, bigger, but similar), I keep the focuser pointed towards the mount, thus keeping the weight as close to the rotation axis as possible. If the focuser and weight (barlow/QHY etc) is in line then there should be no reason to counter-balance it surely.
Gary

Very clever . I'll try this first.

[multiweb (Marc)]

Originally Posted by AlexN

Better idea, you send me your G11, I'll send you my EQ6 + Megrez 102, the 102 will be great with the QHY8 (as it is with mine) and the eq6 is more than enough for the setup.... the G11 will hold my C11 beautifully (and be sexy anodized black) and then everyone is happy (refractors are beautifully easy to balance )

Alex.

No way. I love my G11. Best money I've ever spent on this "hobby".

[kinetic (Steve)]

It might minimise it, but it will still be a problem.

Steve