8" GS Dob mirror cell upgrade - DIY - Page 2

janoskiss (Steve H) · #21 20-08-2005, 09:05 PM

That sounds dangerous Mike B!

janoskiss (Steve H) · #22 27-01-2006, 11:20 PM

An update on the mirror cell mod:

1. This mod should be unnecessary for the current line of 8" Dobs from Bintel. They all have 3-point mirror cells with the support points roughly halfway between edge and centre (not at the edges like mine)

2. Even with my Dob, the mirror being supported only at its very edges seems adequate.

Details
I removed the extra mirror support because I wanted better cooling after having fitted a fan. The fan is magic! (and it's a must have) but I will post about it another time. With the mirror cell restored to edge-support only and the mirror properly cooled, I star tested the scope at 500x and apart from needing a little tweak of the primary alignment there was no sign of mirror sag/pinch. Just a nice round diffraction rings.

PS. Yes I went to all that trouble for nothing. But it was worth doing even only to show it does not need doing.

stringscope (Ian) · #23 28-01-2006, 07:25 AM

Steve,

I agree with you that fans are a must have in solid tube newts.

Cheers,

stinky · #24 28-01-2006, 08:50 AM

For proofing the plywood use a thin epoxy (West) -adds strength and is 100% waterproof - to attach the mirror - a polyurethane compound like Sikaflex is ideal. Both products available at marine stores, larger (good, not Bunnings, -generic - etc.) hardware stores.

janoskiss (Steve H) · #25 28-01-2006, 12:37 PM

Did you even read my last post, stinky?

stinky · #26 28-01-2006, 01:03 PM

Sure did (but didn't notice the dates of the previous posts, - just added on incase anybody elese would like to know the best product for sealing plywood! all be it very late

For the do it yourself tinkerer , ATM'er ply is a great material, easy to work, cheap, versatile but not good in moisture. Epoxy solves that - for the dob boys great way to mod bases... etc etc.

janoskiss (Steve H) · #27 28-01-2006, 01:21 PM

Yes, we are several months past the coating issue.

(Never coated it though and it always held collimation well. I hate using sticky messy chemicals, paint, lacquer etc; wait for it to dry; more coats, more mess...) Anyway, cell mod has been ditched.