My 10" GS Dob REBORN! - Cutting and powder Coating -
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
Very good work. Personally I would not worry about baffles if you are going to paint the inside a really dark/pitch black as this will be a form of flocking and will stop the ambient/off axis light from interferring with your images. When I "flocked" my tube with paint I gave it an initial coat of the stone finish paint that is lumpy to break up the surface then gave that a few coats of dead black flat paint (chalkboard paint).
Another reason to avoid baffles is that they can introduce air currents into your light path.
Thanks guys, I can't wait to get it back from the powder coaters!
Rob, do you know if I would have any issue with paint compatibility if I was to paint the Krylon over a stone effect paint?
To get the Krylon I rang Supply One and they got it in form another store. They have a few stores around town. I seem to remember it being around $15 a can. Although even though everyone seems to rave about this paint I still think it could be blacker. I guess it is the "mattness" that makes it look less black than glossy black.
Very good work. Personally I would not worry about baffles if you are going to paint the inside a really dark/pitch black as this will be a form of flocking and will stop the ambient/off axis light from interferring with your images. When I "flocked" my tube with paint I gave it an initial coat of the stone finish paint that is lumpy to break up the surface then gave that a few coats of dead black flat paint (chalkboard paint).
Another reason to avoid baffles is that they can introduce air currents into your light path.
Another way to get a really dark tube is to paint it flat black, then while the paint is still wet, throw in some sawdust and move the tube around so you get a good even coat. The sawdust should stick to the paint, and when everything is dry, put on another coat of flat black.
Geoff
I have no idea of incompatibility issues but a quick try on some scrap metal (especially since you have a little bit of the exact tube) should give you a result.
crikey! I have had my GSO for longer than most here now i think an I still dont have rust... it seems that I am lucky rather than everyone else being unlucky.
yeah... I've only had my dob for less than a year!
Although it shouldn't happen I do understand that it is a budget scope. I guess you get what you pay for. Although you would think that a good powder coat in the factory would only add $20 to the price.
Hopefully with the new look it will last many years!
I notice what looks like some surface rusting on the inside of my OTA - I'm the second owner, and it was reportedly bought new last November. Maybe I'd better tackle it sometime - let's see how it survives a wet winter and spring? Anyway, I'm getting some good ideas from you guys - thanks.
Eric, don't wait for the rust, stop it now. Galmat make some great no fuss paints that will allow you to "touch up" now and get you through to to a time of refurbishment. Greg.
P.S. The rust could have been set of by a simple relocation.
OK, I'll do a full inspection next chance I get and "touch up" to stop it developing further. I have to admit that I have concentrated on the mirrors and their adjustments to date - haven't really looked elsewhere
Quote:
Originally Posted by taminga16
Eric, don't wait for the rust, stop it now. Galmat make some great no fuss paints that will allow you to "touch up" now and get you through to to a time of refurbishment. Greg.
P.S. The rust could have been set of by a simple relocation.
Ever since I saw the result of Dennis' candy apple red coated dob I have known that when the time comes I'll go the colourful powder coat path as well.
(see the pics in this thread from May last year - at Ron's place, of course!) http://www.iceinspace.com.au/forum/s...ad.php?t=10373
I've been thinking a very nice blue colour would work well too .... so I'm very keen to see the end result Dave, keep us posted.
Last edited by Gargoyle_Steve; 07-04-2007 at 01:05 AM.
That Red dob looks SUPER! If its base was blue it would look like superman! I have been trying to find a pic of Denis' dob on this site but couldn't. Thanks for posting Steve.
My blue should be a bit more tame then that red...
I'm hoping to get it back on Wednesday! I can't wait.
If I remember rightly Dennis was originally going to spend around $70 - but after talking to the powder coater his tube had an undercoat, then 1 or 2 colour coats, and then a clear protective coat - if I remember rightly....
Ok .... so now I went back and searched past threads to check, here's exactly what Dennis said the day before his tube went in for it's treatment:
" Price has gone up but more work required
Well part two of the story goes......
In order to completely stop the rust the guy (whom I have great faith in) is going to acid bath it after the media blasting and prior to first zinc coat, then, because I chose a translucent colour, it will need a white undercoat, then the colour and to top it off he is going to clear coat it, that makes four coats, four visits to the oven, if it aint weatherproof after that then I give up. Total price has jumped to $135 but the minute I saw the colour sample I knew it would be worth it.
I intend to matt black the interior again although he said he should be able to avoid most overspray, flock sounds like hard work and I have reservations about dust from it on the mirror. "
Then when it arrived back Denns had this to say .... (lol)
" Back from the powder coaters Woo hoo, wait till you see the 12" GSO now, talk about from rags to riches, it may not be for everyone but I LIKE IT! A very sexy light metallic ruby red tube (matching candy apple red was too hard for powder) and he even threw on a second clear coat to make it look deeper and richer at no cost. No photo's yet because I want to re-assemble it first and I cant do that until I re-spray flat black on the inside, yes quite a considerable amount of primer overspray got in to the tube. The coating is very tough and hard to scratch so I can highly recommend this to anyone needing to re-coat their tube."
The more I think about this, the keener I am to get my tube powder coated soon!
Thanks Steve. I'm hoping that the sand blasting and zinc rich primer will be enough to stop the rust in its tracks. I couldn't spare the cash for the extra acid bath etc.
Time will tell. Also I am going for just one coat of colour... which is normal for powder coating.
. I will then coat the inside with Krylon ultra flat black.
