Hi Everyone,
I thought some people might be interested to see some of the changes I have been making to my GSO 10" Dob OTA.
Like many GSO dobs it began to show surface rust last week. So I thought I would get in quick and recoat the tube. I didn't fancy sanding all the old paint off then painting it my self so I decided to ship it off to the powder coaters to be sand blasted and re-coated (more about that later).
But I thought this would be a great opportunity to cut the tube down and lift the primary mirror closer so I could achieve focus with my Canon 20D.
Below photos show some of the process. I decided to move the mirror by 35mm, so to mark out where to cut I tightly wrapped a strip of stickers (you could use a continues roll of paper) around the end of the tube and marked the position of the holes. Then I could slide the paper down exactly 35mm and sticky tape it in place.
Then using a 1mm think cutting disc on my angle grinder I easily made a nice straight cut. Those 1mm discs make cutting this sort of material a breeze!
Then using the off-cut metal as a drilling guide I drilled the screw holes.
I also decided to move the OTA pivoting mounts up the tube by one hole to better balance once its all back together. Although the tube now has 4 holes the mounts are large enough that it doesn't show.
I then filed and sanded everything smooth and gave all bare metal a touch of paint to stop rust setting in before it was powder coated.
OFF to the powder coaters where they will sand blast the tube inside and out then prime in and out with zinc rich primer then coat just the outside in "Space Blue" a funky dark blue 
. I will then coat the inside with Krylon ultra flat black.
I do have a question though... Should I do anything else while I have the OTA in pieces? Should I add baffles? Or anything else at this stage?
I will post more pics as soon as the tube returns from the Powder coaters.
By the way... The powder coating and blasting should only cost around $65
Cheers
Dave