Dual Scope Mounting

[slice of heaven]

I'm after opinions on the mounting setup for an 8" F6..10kg and a 4" F10..6.5kg guidescope on an Eq6.

The usual configuration is the under and over setup but after seeing a side by side mounting setup I'm wondering whether this is a better option.

To me it seems to make sense to lower the centre of gravity closer to the head, but I'm a dumb dob pusher and have never crossed to the dark side before.

The ODs of the tubes are 9 5/8" and 6". So theres a fair reduction in hieght if I choose the side by side option.

The link below has a pic of the style of mount Im thinking of using. Its the Duo Mount Pic

http://www.telescope-service.de/moun...start.html#eq6
Telescope-Service Mounts

Thanks guys

[mch62 (Mark)]

Yep that's is a good way to go if your tube is of sufficient over diameter placing extras on top requires more counter weighting.
Another trick to lower the total counter weights requred is to use a single bar bell weight at the end of the counter weight bar instead of several smaller weights along the bar.
The ones nearer to the OTA have less effect than one further out along the bar.

[slice of heaven]

Mark, youve brought up another puzzle I have in your post.
The single weight on the shaft's end I had believed to be the right choice until I read the calculation for weights link below

http://www.robincasady.com/Astro/WeightCalc.html
How much counterweight? - Robin Casady's Astro Accessories

Which is the right choice. He seems to have pretty sound reasoning.

[mch62 (Mark)]

Forgot to mention that in using one large weight **I don't have to have counter weight shaft ALL the way out **. About 3/4.
All the weight is concentrated in one spot closer to the RA axis instead of being spread along the shaft.4 on top of eack other.
what he is saying is correct that the momentum and torque required will be greater with the greater distance for the center of gravity.

I found that using the original multipull weights stacked along the shaft i required more weight and the shaft all the way out to balance my Newtonian.
The other thing to remember is the EQ6 shaft is not as large as say a Losmandy.

I have seen and used four weights on the EQ6 shaft and it has a definate bend to it and wobble when slewed and stopped.That's why I used just one heavy one and the shorter shaft.
You could make the shaft larger but where it goes inside the housing will still be the original size.
I have seen this done else where on the web a shaft made to just slide over the original and was held in place with grub screws.The original was only out about 2" out and this was what fitted inside the larger shaft.

I think for the weight handling of the mount the counter weight shaft could have been about 50% -100% bigger in diameter.
I just like to have things over enginered rather than be under and wobbly.
A wobbly EQ mount is useless for any thing except low power work.
Not sure just how many weights you will require in your set up but I know Tony has a C11 with a 4.5kg guide scope on top and uses the four counter weights.
As your tube is smaller in diameter but your guide scope is heavier I could only make a guess .If you mount it side by side it will have to be less thou.

You could use that formular but another thing to be aware of is the OTA sits a fair way from the RA axis on the EQ6.
From the RA axis center to the dove tail mount is 200mm (A) alone , then you have the diameter of the OTA and then a guide scope and brackets ontop of that.

Mark

[slice of heaven]

Aahh,now that makes sense. I had been misled by another group where extension shafts were being used to reduce the weight needed and not 1 person condemned the idea at all.
Doing rough calculations I'll need 18.5 kgs at the end of a fully extended shaft using the dual mount, compared to 25kgs fully extended using the under and over setup. The weight needed to offset the guidescope is halved when using the dual mount.
How much weight can you hang of the bottom of these units?
Using those calcs above would 25kg on a 3/4 shaft be more acceptable than 20kg on a full shaft or is there a limit where too much counterweight creates other problems?

Thanks for the reply Mark