Orion focuser barrel too big?

I have a Dobsonian 10-inch that I built a few years ago. At the time
I equipped it with a very cheap focuser -- the eyepiece clamps into
the barrel and then the barrel threads in and out to focus. I believe
this is called helical focus. I can't find a web link for what I have
now, but it's plastic and pretty cheap.

So I was looking to upgrade to a rack-and-pinion model, or at least
one that doesn't rotate the eyepiece as it focuses. I don't spend a
lot of time with the scope, but when I do I often set it up in a
semi-public place. So I don't really want to spend $70-$300 on a new
component, but I want to upgrade a bit. I figured that the Orion
basic focuser ($26) would suit me well enough and I ordered that.

http://www.telescope.com/shopping/pr...iProductID=399

I received it yesterday and was surprised to find that my standard
1.25-inch eyepiece was rather loose in the barrel. Certainly I can
tighten down the lock screws, but it still seems kind of loose, and I
don't want to loose collimation every time I bump the eyepiece.

My current cheapo plastic focuser has a much tighter fit. Did I just
get a bad unit?

Also, I search the Meade site for focusers and found nothing. Can
anyone give me any pointers to cheap focusers? Thanks.

There's two ways to hold an EP in the focuser, friction fit with a sprung
end to the tube or use a holding screw.
You got used to one method and now are confronted with the other method. Of
the two, I prefer the holding screw method as that allows for the better EPs
to stay firmly in place.
I'll also note that the EP you have may also be smaller than it should be.
As to a decent focuser, I'd only consider Crayford focusers for the low
price field. Crazy Ed has had focusers of that type for $85 for a while and
probably still has them. Aside from that, it only takes an hour or so to
build a Crayford if you have the tools.

--
There are more Democrats on the Calif. Special Election than Republicans!
Go count if you don't believe me!
Bob May

"Bob May" wrote in message
...
There's two ways to hold an EP in the focuser, friction fit with a sprung
end to the tube or use a holding screw.
You got used to one method and now are confronted with the other method.
Of
the two, I prefer the holding screw method as that allows for the better
EPs
to stay firmly in place.
I'll also note that the EP you have may also be smaller than it should be.
As to a decent focuser, I'd only consider Crayford focusers for the low
price field. Crazy Ed has had focusers of that type for $85 for a while
and
probably still has them. Aside from that, it only takes an hour or so to
build a Crayford if you have the tools.

--
There are more Democrats on the Calif. Special Election than Republicans!
Go count if you don't believe me!
Bob May

General Clark is out to kick some Repub ass!

"Bob May" wrote:
There's two ways to hold an EP in the focuser, friction fit with a sprung
end to the tube or use a holding screw.

Hmmm. This is a spring (leaf, I guess) in the barrel/tube, or on the
eyepiece? Neither were true for me. The Orion focuser had a ring at
the top that was *almost* the right size, and even that part only ran
about 1/4-inch down the axis of the tube; then the tube got even
bigger. So there really wasn't much holding the eyepiece right.

I'll also note that the EP you have may also be smaller than it should be.

I have 2 EPs and a Barlow and they all fit in my old focuser exactly
the same, so I think they're all 1.25", but I'll check again tonight.

As to a decent focuser, I'd only consider Crayford focusers for the low
price field. Crazy Ed has had focusers of that type for $85 for a while and
probably still has them.

Crazy Ed has closed up shop and gone fishin'!

Help! I haven't returned the focuser to Orion yet ...

On 23 Sep 2003 07:28:31 -0700, (Chris Campbell)
wrote:

This is a spring (leaf, I guess) in the barrel/tube, or on the
eyepiece?

The classic Edmund Scientific eyepiece holder was a simple tube with a
T-shaped slot cut in the tubing. The eyepiece was held by friction.
ATMs who made their own eyepiece holders often would buy a chrome
brass 1-1/4" sink drain extension from the hardware store and cut out
the slot.