Monday, August 27, 2012

Meade 12" Lightbridge Mods

Last year on table mountain, I sold my beloved 10" Odyssey Compact.

I sold it to make room for and help finance a larger dob.  I dream of someday owning a 16" to 20" scope but for now I have settled on a 12" Meade Lightbridge that a guy in my astronomy club was selling.

The story is that the scope was damaged in shipping, someone picked up the pieces and pulled a Humpty Dumpty on it.  The base was replaced with what looks like a dobstuff base.  This was ultimately a pretty nice upgrade from the stock Meade base.  The bottom tube was a little dinged up but mechanically everything is in pretty good working order.

The optics on the other hand....

Were in poor shape.

Granted, as far as optics damage goes, it could be much worse.  This is at best a recoat, at worst a slight refigure.

The gall on the side of the mirror is the worst thing about this.

I would like to grind my own mirror some day, so this may be an opportunity to do that.  I don't know when I will get around to that.  

Bottom line, the primary will need replacing but it is still usable.  Field tests yielded satisfactory results and I was able to locate Uranus this year at TMSP.

Being one of the early model lightbridges, it is all white and has a single speed focuser.  Once I talked the seller down to an appropriate price, I started putting my list of modifications together.

Here's a kind of before shot.

Pretty much identical to a stock 12" lightbridge with the exception of the base.  Some loop side Velcro has been added to the altitude bearings to provide a smooth motion against the Teflon pads on the base.

There are also some counterweights that attach via Velcro visible at the bottom of the tube.

First thing I had to do was tear the scope down.

The scope consists of two 14" diameter 1/28" thick steel tubes with some cast aluminum rings which are attached to the tubes with several screws.

A few minutes with a Phillips screwdriver and the scope was mostly disassembled.

The mirror cell and supporting hardware are all attached to the rear aluminum ring.  The mirror is pretty heavy and accounts for most of the scopes weight.

Here are the rings and truss hardware before I dropped them off at NW Powdercoatings which happens to be a few blocks from my house on my way to work.

A week later I picked them up.

 I was quite happy with the results

The new coating is a black crinkle that will help scatter light better than the glossy white rings did previously.

This is also what the newer stock lightbridges use.  Sometime in the last year or so, Meade started painting the rings black, it looks pretty nice and has some performance bonuses as well.

I did end up having to chase all the threaded holes and had to sand some of the tube clamp hardware to get everything to play nicely together again.  Its still a little tight but it will improve as I use it more.

The next piece on my list were the truss poles.  I looked into having them anodized but that was expensive and wasn't exactly what I was looking for.  I looked into using heat shrink tubing but even going with some budget suppliers on ebay was going to cost close to 40 bucks.
Some more reading on the web and someone suggested using the molded foam pipe insulation tubes.
At 2.99 for a 7 foot length, the price was right.  I picked up some Pliobond flexible adhesive.

Its a contact adhesive which requires an initial coat to dry, and a second coat on one side to tacky before adhesion.

 I cut all my tubes to length, inserted a piece of PVC tube I had laying around and set to work applying the adhesive.

This stuff is nasty.

Luckilly I have a nice organic vapor mask that I was able to use.

Currently the glue is drying, as it will take a couple days to reach full strength, then I will slide them onto the truss poles and they will look like this minus the gaps.

I am also considering painting the tube a different color as well.....I hammered out most of the dents in the tube and I think a nice fresh coat of paint would look pretty nice.

Haven't settled on a color yet.

More to follow!

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