Front Of OTA Counter Weight

[JayTee]

Hi All,

Just considering what to use when your AP rig has all that stuff attached to the back end of the OTA and you wind up not having enough travel in the saddle to counter all that rear-end weight. So we need a front weight, something temporary to use as needed.

I put my brain in gear and thought why not velcro adjustable ankle weights? These weights have pockets to add more or less weight to them. Has anyone ever used something like this to balance your OTA + gear on your mount?

Here's what I'm talking about.
https://www.amazon.com/gp/aw/d/B09K4B2J ... th=1&psc=1

[SkyHiker]

Can't you get a longer dovetail? Or saddle? If it has rings, can you move the OTA forward in them? A picture would be nice.

[JayTee]

If it has rings, can you move the OTA forward in them?

The only OTA I have that is attached to the saddle via rings is my ES 102 and it is all the way forward in those rings. The other 2 have the "foot" bolted to the OTA. That's why I was thinking of weird ideas!

[AstroBee]

You'll just want to make sure the ankle weight doesn't shift at all as the scope tracks towards the meridian and does its flip.
My smaller scope is too light for my smallest counterweight so I added a v-style dovetail bar to the top of the scope and have an adjustable weight to help with both R.A. and Dec balance.

[JayTee]

Thank you, Greg,

I actually have all your shown hardware in my "extra" hardware box. What I was trying to do was provide equal weight all the way around the OTA to minimize the side torque caused by a single-point weight source. BUT I forgot about nylon fabric on an enameled slick OTA and the slippage that might cause -- slippage is BAD! Hmmm. Back to the drawing board -- maybe.

[OzEclipse]

My VC200L astrograph has no front corrector like a SCT. That is one of the reasons I like it so much. The corrector is in the baffle tube. Consequently, the 8 inch mirror, baffle tube, correctors, focuser and diagonal and eyepiece or the camera train all sit at the back of the tube making it very rear heavy.

I made my own adjustable front counter weight. These brass weights weigh 500g each. Rather than clamping to a central shaft, they are threaded so that they just screw into each other with a felt pad on each that provides enough friction to stop them unwinding. No bounce or wobble. Hanging them down towards the polar axis reduces the moment and minimises need for any extra counterweighting or mount loading.

I have three x 500g weights (1.5kg total) that can be added in 500 g increments. Then they are attached to a GSO dovetail puck which can slide up and down the tube's dovetail rail allowing fine adjustment.

Joe

[Juno16]

Is the scope ring stopping at the finder bracket?
Can it be removed?

[JayTee]

Is the scope ring stopping at the finder bracket?
Can it be removed?

The finder bracket has been removed to get the rings as far back as they will go. We're talking about my ES 102 ED and once I put on the new filter wheel with filters I'm afraid I will not be able to achieve balance at that point. So a forward weight now becomes necessary. I was just trying to think out of the box to come up with a non-point source of counter-weight.

I think I'll look for a way to make that weight belt a bit "sticky" so it doesn't slip and yet doesn't mar the OTA. OR I could attach some thin aluminum strips that would bend over the edge of the dew shield and that should affix them. Hmmm.

[OzEclipse]

Is the scope ring stopping at the finder bracket?
Can it be removed?

The finder bracket has been removed to get the rings as far back as they will go. We're talking about my ES 102 ED and once I put on the new filter wheel with filters I'm afraid I will not be able to achieve balance at that point. So a forward weight now becomes necessary. I was just trying to think out of the box to come up with a non-point source of counter-weight.

I think I'll look for a way to make that weight belt a bit "sticky" so it doesn't slip and yet doesn't mar the OTA. OR I could attach some thin aluminum strips that would bend over the edge of the dew shield and that should affix them. Hmmm.

Providing you don't need to adjust the weights, you can buy some very large screw up hose clamps that should secure the weight belt.

I have a Stellavue 102ED and need a similar arrangement. The scope is held by tube rings attached to a short Losmandy D rail. So I thought about this problem and came up with this solution

You could also glue some lead fishing weights to the non-moving circumference of the first type shown above. Then use self adhesive felt pads on the inside.

Aluminium strips over the lens hood may cause diffraction spikes and won't prevent shifting during tracking.

Another way is to buy some PVC plumbing pipe that is just a touch too small to fit over your lens hood.
Cut a slot in the tube so that it can be pried apart and will spring close over the lens hood. Glue some long thin lead weights to the outside with a flexible adhesive such as structural silicon or a contact adhesive. The interior can have some self-adhesive felt pads affixed to prevent damage to the OTA.

You don't want to be handling a lot of lead to guard against risk of accidental ingestion. Eg attach the weight hood then have a cup of tea and a biscuit.
So a layer of spray on exterior flexible roof and gutter sealant over the exterior part with the exposed lead should protect you from lead exposure.

Joe

[JayTee]

Brilliant idea Joe. It could also be used as a lens hood extender for even better dew control!

[Juno16]

Is the scope ring stopping at the finder bracket?
Can it be removed?

The finder bracket has been removed to get the rings as far back as they will go. We're talking about my ES 102 ED and once I put on the new filter wheel with filters I'm afraid I will not be able to achieve balance at that point. So a forward weight now becomes necessary. I was just trying to think out of the box to come up with a non-point source of counter-weight.

I think I'll look for a way to make that weight belt a bit "sticky" so it doesn't slip and yet doesn't mar the OTA. OR I could attach some thin aluminum strips that would bend over the edge of the dew shield and that should affix them. Hmmm.

My rings are slid on the finder bracket and I have to clamp in the dovetail almost to the end.
Your setup is similar to mine except for the filter wheel (I use a filter drawer).

Joe’s @OzEclipse clamp idea is a great solution to locking down the weights.

Let us know how it works out.

[OzEclipse]

Is the scope ring stopping at the finder bracket?
Can it be removed?

The finder bracket has been removed to get the rings as far back as they will go. We're talking about my ES 102 ED and once I put on the new filter wheel with filters I'm afraid I will not be able to achieve balance at that point. So a forward weight now becomes necessary. I was just trying to think out of the box to come up with a non-point source of counter-weight.

I think I'll look for a way to make that weight belt a bit "sticky" so it doesn't slip and yet doesn't mar the OTA. OR I could attach some thin aluminum strips that would bend over the edge of the dew shield and that should affix them. Hmmm.

My rings are slid on the finder bracket and I have to clamp in the dovetail almost to the end.
Your setup is similar to mine except for the filter wheel (I use a filter drawer).

Joe’s @OzEclipse clamp idea is a great solution to locking down the weights.

Let us know how it works out.

Jim,

Success of the PVC pipe clamp idea critically depends upon being able to source PVC pipe the right size for your lens hood. This will vary from scope to scope.

Joe

[JayTee]

Jim,

The success of the PVC pipe clamp idea critically depends upon being able to source PVC pipe the right size for your lens hood. This will vary from scope to scope.

Joe

So true Joe.

That thought has already crossed my mind, but so have improvements from my simplistic brain.

After you get the fit around the lens hood just right you could then position 3 flathead screws projecting out from the PVC at 120° intervals around the tube. These screws would be used as an attachment point for "large-ish" fender washers as a weight source. You can then load up each screw with as many washers as needed and then simply bolt them in place. This method even allows for correcting any off-axis torsion that may already exist.

This idea just keeps getting better. I may try to build one today or tomorrow. Don't worry, I'll take pictures.

Cheers,

[JayTee]

I just ordered one of these. It appears to be a custom fit for my lens hood. It even has the hose clamps. So all I need to do is drill 3 holes and go buy some big fender washers. YAY!

https://www.supplyhouse.com/Bluefin-FRC ... CsQAvD_BwE

[OzEclipse]

I just ordered one of these. It appears to be a custom fit for my lens hood. It even has the hose clamps. So all I need to do is drill 3 holes and go buy some big fender washers. YAY!

https://www.supplyhouse.com/Bluefin-FRC ... CsQAvD_BwE

Even if not an exact fit, rubber is easy to cut to either open it up or close it down. I might look for an Australian supplier of the same. If it's a loose fit, you could glue some heater cartridges on the inside and these could heat the metal lens hood and act as a dewstrap heater.

Joe