Has anyone slapped a 12" lightbridge on to an EQ6 mount?

[White Rabbit]

I'm thinking of buying both as a posed to a "12 solid tube newt for more portability for camping and things. Can anyone see a problem with this? The only thing I can see that might go wrong is the tube rings putting pressure on the truss and making the scope curve a little.

Thanks
Sandy

[spacezebra]

Check out the Yahoo - lightbridge group forum - I have seen a pic on a EQ mount - but not sure if it is a EQ6.

Cheers Petra

[iceman]

What sort of rings can you get for that?
I'm having enough trouble trying to get proper rings for my solid tube 12".

[gary]

Hi Sandy,

Don't go there. :)

Truss poles can be used to replace the solid tube of a large aperture Dob
because, by calculation and design, the secondary cage is designed to be
light.

Truss pole selection is a major factor in the performance of truss pole
telescopes. Borrowing from the world of mechanical engineering, a truss
deforms under stress. The deformation is proportional to the force applied
multipled by the length of the truss cubed, and divided by the outer
diameter of the truss to the fourth power minus the inner diameter of the
truss to the fourth power.

Normally, by design, the force is the weight of the secondary cage.

If you were to somehow support the scope by the trusses, the force would
become very large, as it would include not just the weight of the secondary
but the entire primary.

The scope would not just 'curve a little'. It would curve a lot. If it didn't
mechanically and catastrophically fail under load, the bending truss would
provide terrible optical performace as the primary and secondary go out of
alignment.

There are also serious considerations with regards the primary mirror.
Though the mirrors in the LB's tend to be thicker than premium Dobs
(this is a disadvantage, since they take much longer to cool when compared to
a premium scope with a large thin mirror), the mirror support in either case
is designed for when the scope is used sitting on the ground in an Alt/Az
configuration.

Suggest you just stick to the truss pole scope and leave the massive EQ6 at
home when on the camping trip and if you are doing visual observing.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

[Alchemy]

In reply to ring manufacture for 12" tube (364mm diameter) in Melbourne for those lucky enough to live here Look up IMF -Innovative Metal Fabrication in Bayswater he made me a set out of stainless steel for $300.00.
They work fine.....Id send a picture but i cant get the picture thing to work.

[White Rabbit]

Hi, I hadnt actually seen any, but figured they would be available even if you have to source them yourself.
I'm just spit balling at the moment, I'm looking to upgrade from my ETX125. I'm over the mount on the meade and I crave more light.:) I have about 6 months before I can buy, and I dont want to rush into it like I did with the ETX.

Thanks
Sandy

[White Rabbit]

Thanks Gary,

As I said above I'm just spit balling here so thank you for the detailed response.

Sandy

[Aster]

Hi Mike,

Why not make a standard wooden cradle ???

Made one myself out of 15mm exterior plywood, glued and screwed. Attached dove tail alluminium bar, 38cm long, with 4 by 6mm metal bolts. No problems so far. Needed an extra 1kg in counterwieght.

Regards
Alexander

[erick]

I knew that :whistle:



First banana-shaped reflector?


Seriously, it sounded highly improbably to me that it would work with a standard truss design.

[gary]

No problem! Nothing wrong with spit balling and that's why we are all here. :)

However, unless you want something that resembles the bridge that
collapsed in Minneapolis earlier this month, don't go hoisting that LB 12
onto an eq mount using rings of any sort. ;)

When you first get a truss pole Dob disassembled, a couple of things
strike you when you pick up the parts.

When you pick up the top end cage, you tend to think, "Boy, this is light!".

When you pick up the mirror and rocker box, you tend to think, "Geeze! This is
heavy!"

That very heavy bottom end you just can't go whirling around in the air. Apart from the
weight, the mirrors are designed to sit in there assuming the scope is on reasonably
level ground. On some Dobs, tip them over far enough and the mirror will
just fall out of the box. It's own weight is what is designed to keep it in there
on the assumption the scope is sitting on the ground.

Some personal views on scope selection having looked through a lot
of them -

Nothing beats aperture. However, some of the key differences between the
low cost Dobsonians and the premium Dobsonians, like an Obsession or
a locally made SDM, is that the premium scopes use very thin mirrors that
are designed to cool down quickly. The thermal mass of a larger, thick
mirror is such that you can spend much of the night waiting for the mirror
to cool and if it is not cool, the optical peformance will suffer. However,
Dobs get away using thinner mirrors than some other designs
by having (hopefully) carefully designed mirror cells (mechanical supports)
that are designed to keep the mirror figured (i.e. stop it from warping under
its own weight).

Strictly speaking, according to their designers, many Dobs aren't
even designed to sit on top of an equatorial table let alone an equatorial mount,
as the cell design is then pushed beyond what it was designed to do.

One other feature that differentiates the premium Dobs from the low-cost
generics is the smoothness of their motion. The best ones have just the
right amount of stiction - what Dave Kriege describes as "buttery smooth".
You push it and it moves without hesitation and you stop pushing and it stops.
So in that regard, premium Dobs have migtrated from simply being an
implementation of a simple and low cost style of mount to what might
be described as a "driving experience". They feel good when you move them
and it gives you the type of control and smoothness of a high performance
car. In my opinion, this 'feel' is as much a part of the expereince as the
view through the eyepiece, because if one is frustrated with the movement, then
it distracts from the viewing.

If you haven't done so already, if you spot a premium truss pole Dob
at a star party, ask the owner if they mind if you could have a look through
it and be allowed to give it a push. Even if you aren't about to run out and
buy one, like the opportunity of driving a really high performance car,
its fun and you appreciate how good things can get.

Were you interested in astrophotography as well, hence the question with
regard the EQ6?

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

[White Rabbit]

Hi Garry.

Yes, I would like to get into a bit of photography with it so thats why I was looking at the mount. Nothing serious just for fun.

It also has to be easy to use so that it doesn't daunt my girlfriend, it's important that she keeps interested in it too, that way she wont mind as much when she finds me with knew gear ;).

Thanks again for the detailed response.

Sandy

[gary]

Hi Sandy,

Good stuff.

If you are going with the EQ-6, consider something like a solid tube reflector
that is reasonably "fast", like f/5 or better.

As most astrophotography tends to be a bit like an iceberg, with 75% of the work
going on 'beneath the surface' in the post-processing when you get back home,
it requires a lot of patience when in the field and this may not be everyone's
cup of tea while you stand around in the cold and dark doing the actual imagery.
There are other systems that can provide a certain amount of real-time imagery
that can provide more instant gratification, but in that regard, visual observing then
becomes hard to beat. I would recommend to think carefully as to exactly what you
want to do as serious astrophotography is a "boots and all" affair. :)

When you go to star parties, whereas a sizeable group of animated visual observers
sharing the views through one scope is not uncommon, most astrophotographers
tend to be by comparison solitary and quiet when doing their thing. ;)

Best Regards

Gary

[mch62]

another problem is a long tube of any sort on the EQ6 is a no go.
There is to much torque in moving the long tube for the EQ6.
I mounted my truss tube Newt on my old EQ6 just to try the optics and although it tracked ok any wind or tracking adjustment took ages to settle down with massive wobbles.

[JimmyH155]

I agree entirely with Garry, NEVER PUT A TRUSS DOB ON A MOUNT. Just looking at my 12"LB, the thought of it dangling from a mount is too frightening to contemplate:eyepop:

[White Rabbit]

I was actaully looking at Icemans set up. He has a 12" solid tube on an eq6. I go camping alot and every January I go on a road trip for about a month so I wanted something that catches a lot of light and is also portable. The light bridge seemed to good to be true lol.

Thanks guys

[astro_nutt]

Hey iceman!..
I think I saw an article a while back of someone making a set of rings from clamps normally used to secure LP gas cylinders to caravans then mounted them onto a dovetail plate....I can't remember who it was???

[rmcpb]

Ken, the Snake Valley modifier did the paint drum rings I think.

[iceman]

yeh I saw his thread on that, and it does look do-able.
I'm waiting for a set from Orion Optics in the UK but have had some negative experiences. Hopefully they'll fit this time.

[jase]

If you're looking for tube rings, these guys have a good selection - http://www.parallaxinstruments.com/ring.htm