Focusers and OTA wobble

On Sat, 4 Oct 2003 17:15:35 +0000 (UTC), "Janet"
wrote:

I have a Europa 250 and while I'm generally quite pleased with it one thing
that gets by goat is that whenever I adjust the focus the whole damn tube
shifts and wobbles.

Does anyone know of any gadgets that might be useful to reduce this? I've
heard of zero image-shift focusers but don't know what they are. I also
don't know whether a sturdier mount will make any difference: I use an EQ5.

It is indeed a bit of a pain. I have a Europa 250 and a Vixen apo
refractor. Using them together really brings out the difference in
the quality of the components. However, the Europa is intended to be
a budget scope so I guess it's not fair to be too critical.

I've tried to image with the Europa and the image shift is a
nightmare. Mine is quite old now so I don't know if its the same as
yours but my focusser is a basic rack and pinion affair. A plate on
the 'bottom' of the focusser to a degree controls the stiffness of the
focussing action. If you slightly loosen the four screws that hold
this plate into place it may make the focussing action easier. Be
careful not to loosen to far and lose the screws.
--
Pete
Homepage at http://www.pbl33.co.uk
CCD/digicam astronomy

Janet wrote:
I have a Europa 250 and while I'm generally quite pleased with it one thing
that gets by goat is that whenever I adjust the focus the whole damn tube
shifts and wobbles.

Does anyone know of any gadgets that might be useful to reduce this? I've
heard of zero image-shift focusers but don't know what they are. I also
don't know whether a sturdier mount will make any difference: I use an EQ5.

Cheers


This isn't bad scope, but the tripod is what's making things shaky.
You can do a couple of things. You can make sure the bolts attaching
the extruded aluminum legs to the mount are tight. You could take the
legs to a cabinet shop and have them make some oak legs and throw the
aluminum ones away. This will likely do more than anything else to quell
your shakes.
Zero image shift focusers are intened for use in catadioptic
(Schmidt-cassegrain) scopes, which sometimes suffer from image shift due
to wobble in the mirror when the focuser knob is turned. The zero image
shift focuser will do nothing to help your shakes.
There is a fellow in the US that makes legs specifically for the CG-5
type mounts. His website is http://www.alsastro.com
I purchased a set of his legs for my tripod and the shakes vanished.
You could also do a search for articles on improving the CG-5 mount,
which is essentially what you appear to have. There are a number of
helpful sites that discuss simple remedies for making your mount and
tripod more useable.
Good luck to you.
Etok
Mill Valley, California
(remove spamblock from email to reply)


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Hi

You may want to consider just filling the legs with expanding foam bought
from any hard ware store for about a fiver to help eliminate the vibration,
it does help.


"Etok" wrote in message
...
Janet wrote:
I have a Europa 250 and while I'm generally quite pleased with it one
thing
that gets by goat is that whenever I adjust the focus the whole damn
tube
shifts and wobbles.

Does anyone know of any gadgets that might be useful to reduce this?
I've
heard of zero image-shift focusers but don't know what they are. I also
don't know whether a sturdier mount will make any difference: I use an
EQ5.

Cheers


This isn't bad scope, but the tripod is what's making things shaky.
You can do a couple of things. You can make sure the bolts attaching
the extruded aluminum legs to the mount are tight. You could take the
legs to a cabinet shop and have them make some oak legs and throw the
aluminum ones away. This will likely do more than anything else to quell
your shakes.
Zero image shift focusers are intened for use in catadioptic
(Schmidt-cassegrain) scopes, which sometimes suffer from image shift due
to wobble in the mirror when the focuser knob is turned. The zero image
shift focuser will do nothing to help your shakes.
There is a fellow in the US that makes legs specifically for the CG-5
type mounts. His website is http://www.alsastro.com
I purchased a set of his legs for my tripod and the shakes vanished.
You could also do a search for articles on improving the CG-5 mount,
which is essentially what you appear to have. There are a number of
helpful sites that discuss simple remedies for making your mount and
tripod more useable.
Good luck to you.
Etok
Mill Valley, California
(remove spamblock from email to reply)



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___
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Hi,

Just like Etok said, the weak spot is likely to be the EQ5 tripod. I used
an EQ5 for a while and replaced the tripod with a pier. It made such a
difference. The EQ5 /CG-5) is an OK mount once you "fix" the tripod.

Best wishes and clear skies.

--

/Paul B, York, UK.
http://homepages.tesco.net/paul.buglass/astrohome.htm


"Janet" wrote in message
...
I have a Europa 250 and while I'm generally quite pleased with it one
thing
that gets by goat is that whenever I adjust the focus the whole damn tube
shifts and wobbles.

Does anyone know of any gadgets that might be useful to reduce this? I've
heard of zero image-shift focusers but don't know what they are. I also
don't know whether a sturdier mount will make any difference: I use an
EQ5.

Cheers