Build advice please ..

[ZeroID (Brent)]

Hi Peter, Thanks for the link. I thought about a Lazy Susan, maybe it will be a later mod. This thing is designed to be modded as I mentioned. I've printed out new setting circles at work that fit the base and side bearings so they will go on shortly along with an indicator, level and red light system.

Phil, Spotted the 10"f5, not sure how much it would cost to recoat over here and haven't found anyone to do it. I beleive there is a crowd out West Auckland. I also already have Bintel holding me one from the next shipment along with a secondary available end of August so will stick with the plan I think.

I have also finalised my secondary spider and hub construction plans. Some what different from anything I've seen anywhere else. Was trying to provide rigidity and ease of collimation and not keen on the three screw alignment system. I'll post pics of that for comment as I go.

[ZeroID (Brent)]

Just contacted BINTEL and they have my mirrors. Awaiting confirmation of dispatch, and the price was good too !! Thanks Guys, you get my nod.

[ZeroID (Brent)]

The mirrors are on their way, should be here in a day or two so I had a real session over the weekend getting the scope closer to done.
Built my spider, built the UTA, repositioned the altitude bearings. What a mission !!
Here's a few pix to see where it at now.
The 'raw' spider in it's aluminium build
Black Spider sitting in the UTA box
Looking up the UTA at diagonal mount.
The Packdown mode for transport after removal of the alum tubes. It's just on 650mm high. Still some top covers to be made to protect various structures. I'll cutthe upper tubes a little more so it is sitting flush on the cell box.
Couple of shots of the base construction including the butchered teflon automotive gasket and the adjustable feet beneath. Azimuth ring markers to be made a glued before the rocker box is fitted.

[ZeroID (Brent)]

The spider in it's deconstructed state. The front 'beariing' that acts as the alignment pivot is a couple more of those ubiquitous neoprene copier rollers. Crushed up against the back of the wooden diag base. I'll drill a couple of holes through that and add internal heating later. Might also try to isolate one spider leg pair and use the legs as the power conductors so no wires needed.

Also a shot of the whole scope assembled in my incredibly messy garage. I might even clean the place up after this is done.

[ZeroID (Brent)]

Got home last night and there they were all boxed up and waiting. Had a careful peek inside and all is good. Thanks Bintel once again.

Now I'm faced with a problem. I worry about the security of the diagonal hanging above the primary and my diagonal support has no flat surface (yet) to bond to. I want to add internal heating later so have the back surface exposed partially to the heater 'elements' inside to facilitate thermal transfer.

I am think of fixing some fine steel mesh cut from some instrumentation cabinets as a platform. This is thin panel steel full of small holes, about 1/8" diameter. Fix that as the flat diag support to the alum tube. Then bond the mirror at three points with aquarium silastic. The silastic will lock through a few of the holes thus securing it and the remaining holes will help expose the rear of the diag to the heater warmth and the metal is a good heat conductor as well.

I could make the mesh big enough to form small fingers to clasp the mirror gently at the sides, bottom etc. Use a bit of silastic between each finger and the glass edge. I still worry about it falling out although I know the fingers will intrude marginally into the light path. Am I being paranoid or over cautious?

Any other suggestions ?

Is there a better adhesive for glass ? ( I might do some glass/metal bonding tests to reassure my concerns ).

Techniques to ensure adhesion ? ( Alcohol cleaning eg )

Maybe I worry too much ....

[mental4astro (Alexander)]

I used silicone to adhere the secondary mirror to the holder of my 10". That was done in 1996. Still there and no sign of giveing up the ghost. Remember also that your gear is not left outside in the elements to accelerate the deteoriation of the goo. No little fingers reaching around onto the silvered surface.

If you are looking to make a temporary fixture, the same goo could be used to attach the secondary to the lip of the holder shown in your picture below. A bead all along the lip. If you would like a little more mechanical retention, drill a series of little hole close to the lip so that the silicone reaches through these holes back onto itself.

I suggest this material and method as when you are ready to fit the heating element, the silicone can the cut to free the two components. As the silvered surface of the secondary is not the face being glued, you don't need to fear damaging the precious surface. If you already have the aquarium goo, see that it will adhere to the metal. Usually not a problem.

Alcohol wipe and a good dry is a good idea, and won't affect the bond.

[ZeroID (Brent)]

Thanks Alex for the reassurance. I'l buy a new tube of goo so it's fresh and I'll still secure a mesh backing inside the alum tube first so it has more than just an edge retention. Scrub the finger idea. Shouldn't need to cut the adhesive. The alum tube will be secured to the wooden backing disk with three small screws so it can be pulled forward giving access to the interior for later work on heater install etc.

Got to be ready for mods ... always.