How much should my refractor slide in its rings?

My 4" refractor is used with an equitorial mount. It took awhile to find
mounting rings that were the right size. The rings are lined with felt and fit
the tube snugly, but they do not grip it hard enough to prevent it from sliding
when at a severe angle.

So I bought a large rubber plumbing fitting that has a hose clamp. It fits
around the tube and acts as a stop to prevent it from sliding down. This
arrangement works but I'd like to hear from others on how their setup works.

On the one hand, you need to be able to rotate and slide the tube to change its
balance and position. On the other hand you need to be able to lock it down and
secure it in any one position.

With an ideal setup how should this work? Do the rings hold it tightly and you
need to loosen them to make position adjustments? Or does everybody's tube
slide down when looking high in the sky?

Thanks for your help.

Bruce W...1 wrote:

My 4" refractor is used with an equitorial mount. It took awhile to find
mounting rings that were the right size. The rings are lined with felt and fit
the tube snugly, but they do not grip it hard enough to prevent it from sliding
when at a severe angle.

So I bought a large rubber plumbing fitting that has a hose clamp. It fits
around the tube and acts as a stop to prevent it from sliding down. This
arrangement works but I'd like to hear from others on how their setup works.

On the one hand, you need to be able to rotate and slide the tube to change its
balance and position. On the other hand you need to be able to lock it down and
secure it in any one position.

With an ideal setup how should this work? Do the rings hold it tightly and you
need to loosen them to make position adjustments? Or does everybody's tube
slide down when looking high in the sky?

Thanks for your help.


I don't think it should slide at all if the rings are suffiently tight.
Perhaps the solution to a problem I recently
had may be of some benefit: I have an Orion AstroView 120 refractor
which had a significant problem with
vibration. At 150X the vibration from a gentle focus adjustment or even
a camera shutter was noticable for
8-10 seconds. Like your scope, the rings have a felt lining. My
solution was to reline the rings with
pieces of adhesive-backed weather stripping, about 1/4 inch thick. It
reduced the vibration by at least half,
and it could be a solution to your problem.

Hope this helps,
Dale

Bruce it sounds like your rings are indeed just enough to big to correctly
fit your rings. You will need to insert either additional felt or rubber
between your tube and the Mounting rings or attempt to find a set that fits
correctly if your are really concerned about adjusting your rings a lot.

For what it is worth, although I use a Newtonian, on an EQ mount I have my
rings loose and have added an extra clamp around the scope above the rings,
so that I can rotate my tube if the eyepiece position is badly placed,
allowing me to reposition the focuser.

That being said, I still have enough drag on the tube so that it cannot
slide out of the rings, should the scope get pointed in the wrong position.

--
Clear Skies!

========
Tim Longwell
Black River Astronomical Society
http://junior.apk.net/~arstar50/BlackRiver.index.html
Elyria, Ohio


=========

"Bruce W...1" wrote in message
...
My 4" refractor is used with an equitorial mount. It took awhile to find
mounting rings that were the right size. The rings are lined with felt
and fit
the tube snugly, but they do not grip it hard enough to prevent it from
sliding
when at a severe angle.

So I bought a large rubber plumbing fitting that has a hose clamp. It
fits
around the tube and acts as a stop to prevent it from sliding down. This
arrangement works but I'd like to hear from others on how their setup
works.

On the one hand, you need to be able to rotate and slide the tube to
change its
balance and position. On the other hand you need to be able to lock it
down and
secure it in any one position.

With an ideal setup how should this work? Do the rings hold it tightly
and you
need to loosen them to make position adjustments? Or does everybody's
tube
slide down when looking high in the sky?

Thanks for your help.

In message , Bruce W...1
writes
My 4" refractor is used with an equitorial mount. It took awhile to find
mounting rings that were the right size. The rings are lined with felt and fit
the tube snugly, but they do not grip it hard enough to prevent it from sliding
when at a severe angle.

So I bought a large rubber plumbing fitting that has a hose clamp. It fits
around the tube and acts as a stop to prevent it from sliding down. This
arrangement works but I'd like to hear from others on how their setup works.

On the one hand, you need to be able to rotate and slide the tube to change its
balance and position. On the other hand you need to be able to lock it
down and
secure it in any one position.

With an ideal setup how should this work? Do the rings hold it tightly and you
need to loosen them to make position adjustments? Or does everybody's tube
slide down when looking high in the sky?

I own a 10 inch Newtonian reflector that has exactly the sort of ring
you describe (it came with it as a standard fitting, made of the same
felt lined aluminium as the tube rings, and has a camera bracket). The
securing ring is tightened enough so it won't slip and the rings fixing
the tube to the mount are quite loose. There's a picture on my web site
www.merseia.fsnet.co.uk {shameless advert !)
Another approach I've seen illustrated is to have a sliding weight on a
rail with a screw you tighten when the tube is in balance.
--
"Forty millions of miles it was from us, more than forty millions of miles of
void"

Jonathan Silverlight wrote:


I own a 10 inch Newtonian reflector that has exactly the sort of ring
you describe (it came with it as a standard fitting, made of the same
felt lined aluminium as the tube rings, and has a camera bracket). The
securing ring is tightened enough so it won't slip and the rings fixing
the tube to the mount are quite loose. There's a picture on my web site
www.merseia.fsnet.co.uk {shameless advert !)
Another approach I've seen illustrated is to have a sliding weight on a
rail with a screw you tighten when the tube is in balance.
--
"Forty millions of miles it was from us, more than forty millions of miles of
void"
================================================== ====

The slider is a good idea. For that matter a string or dowel rod connected
between the tube and the rings would work. Hmmm, must think about this.

On Mon, 08 Sep 2003 13:48:45 -0400, "Bruce W...1"
wrote:

My 4" refractor is used with an equitorial mount. It took awhile to find
mounting rings that were the right size. The rings are lined with felt and fit
the tube snugly, but they do not grip it hard enough to prevent it from sliding
when at a severe angle.

You need to have the option to clamp the tube securely without putting
too much pressure on it.

So I bought a large rubber plumbing fitting that has a hose clamp. It fits
around the tube and acts as a stop to prevent it from sliding down. This
arrangement works but I'd like to hear from others on how their setup works.

My alignment scope is mounted inside two rings that are quite a bit
larger than the scope. It then uses plastic screws to hold the scope.

For a larger scope I'd use two pair of concentric rings
The inner one should just fit nicely over the tube. the outer one
should be strong enough to hold the screws that press against the
inner one. When tightened they only have to distort the plastic
slightly to grip the telescope tube securely.

That is about as simple a mount as I can visualize.


On the one hand, you need to be able to rotate and slide the tube to change its
balance and position. On the other hand you need to be able to lock it down and
secure it in any one position.

That is why you have a set of balance weights. You should not have to
move the scope in the mount as it rotates, or you view at different
angles.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)


With an ideal setup how should this work? Do the rings hold it tightly and you
need to loosen them to make position adjustments? Or does everybody's tube
slide down when looking high in the sky?

Thanks for your help.