[Lvas] refurbishing telescope

[Fred Rayworth]

Thomm,

 

The focuser should be relatively easy to change. However, the trick may be drilling (or cutting) a larger hole in the tube to accomodate the 1 1/4" draw tube. Sometimes, the hole is already overlarge and you can just slip on the new focuser. However, if it isn't, you'll have to enlarge the hole, and getting it perfectly round is not an option. You can get it "close enough for government work" as they say, but luckily, the focuser flange will cover up the mess, at least on the outside of the tube.

 

First thing to do is take the mirror and diagonal out of the tube, just to avoid accidents and metal or plastic or cardboard shavings (depending on tube composition). Then take off the old focuser and put the new one up against the tube where it is supposed to go. If the tube will rack up past the base, you can rub some crayon or other marker on the end of the tube (don't forget to wipe it off afterward). With the focuser in place, rack it in until the draw tube hits the main telescope tube. That will give you an approximate mark for how big the hole has to be.

 

Cutting the hole is the tricky part. You can't really use a drill and a hole saw because not only don't you have a center hole guide, but just the slightest twist can warp the tube and the focuser many not fit square to the optical plane. You have to cut it by hand with either a hacksaw, or if you have one, a Dremel tool and one of the cutter heads. Just keep in mind, the hole isn't going to be perfect, so worry mainly about getting enough clearance for the draw tube to fit without binding. After you have a decent hole, file off the rough edges. Then redrill the mount holes, if needed, and you are set. Once that is done, get some flat black paint, and spray the inside area around the new holes. Mount the focuser and make sure it works properly, then vacuum out the tube and reinstall the optics.

 

40+ years of telescope making have taught me a few things. Others out there may have a more brilliant plan, but that's how I'd tackle it.

 

One more option, is that the diagonal mirror, the little oval mirror in the center of the spider vanes, may be sized for .965" eyepieces, so going to 1 1/4" may not have an optical advantge. You could just go for a .965" to 1 1/4" adapter and try that. Personally, I'd go for a new focuser anyway, just for the later convenience, but that's just me.

 

Fred

 

 


 


From: ThommKatt69 at aol.com
Date: Sun, 19 Jul 2009 16:53:53 -0400
To: lvas at lvlug.org
Subject: [Lvas] refurbishing telescope


are there any members with experience refurbishing reflectors
was given a Meade 4400 
but it's a .965 set up and want to upgrade scope to 1.25 and pretty much clean up and renew most of the scope..it's actually in very good shape other wise
plus where do I go on the site to Join the Club or is that better done at a meeting



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