The Giant Binocular

[savarin]

Your idea has merit but not using the satellite dish.
I will be flexing the 12" mirrors like this
http://www.skyandtelescope.com/wp-content/uploads/Adler-MirrorFlex.pdf
It may be worth experimenting with the largest circle you could cut from those mirrors, supporting it on a rubber ring and just sucking some air out from the back.
I dont believe it would form a perfect paraboloid but a bunch of them would be a pretty good death ray solar collector.

 

[dtsh]

Coming along nicely.

It's amazing how simple the process really is to make a parabolic mirror. It's complex and takes some effort to understand, but the test methods (Foucault, Ronchi, etc) are pretty simple process-wise and well within the ability of a person with what would be considered today to be quite primitive tech, a dark room, a light source, and a fine straight edge(s).

I've ground two mirrors by hand, it's time consumming but one can achieve very fine tolerances (fractions of a wavelength of error) using such methods. I don't envy you the work of getting two mirrors figured to the same focal length, but I look forward to seeing how you manage it as the build progresses.

Edit: I didn't see if you had mentioned it, but what's the F ratio, looks to be 6 or maybe slower?

 

[savarin]

Yep, its F6, have a look at the first post as it shows how I'm going to get the hogging out to the same size.
I've done one normal 8" f6 but smashed it when it was almost finished but a friend has a spherical 8" f3.7or 8 or 9 (cant remember exactly) with a superb surface that I ground the back surface to the same ROC as the front and flexed into an awesome mirror.
I will be using steel tools for fine grinding so they wont wear away much then pitch for polishing.
I can use Foucault or Ronchi and test the sphere to a null. Easier than testing a paraboloid. This also has the advantage of showing every faint surface blemish so I'm hopeful I can produce a superb surface that wont need to be roughed up again with manual figuring.
This will be well into the new year before I get that far.

 

[ch2co]

Don’t forget, PICTURES,Pictures, PICTURES!​

 

[savarin]

DONT PANIC!
There will be heaps when there is something actually happening.

 

[ch2co]

DONT PANIC!

You took that saying from the hitchhikers guide to the galaxy, didn't you.
Just remember to always have your towel.

 

[savarin]

 

[savarin]

Both rotating top cages and their focusser plates done and the side plates done.
My plan was for the balance point to be approximately 60mm down from the top edge of the side plates.
A quick test showed it to be around 110mm down.
However this is without the weight of the secondary and tertiary and eyepieces in place.
So with those and the full mirror cell I think I am on the right track.
Next job is to obtain two 50mm thich slices from this 100mm dia billet but I do not have access to a powered hacksaw or band saw.



Any guesses as to if its possible to part it?
Looks a teeny bit too much to me

 

[Bob Korves]

Part it off part of the way to get a square cut started and then use a hack saw to finish it if necessary? Surface speed might be a bit high on your 9x20 at the beginning.

 

[savarin]

done sir, I cant believe I managed to get this far through before resorting to the hacksaw.
When I extended the blade that much I had to insert it into the cut as I slid it onto the tool holder.



Started turning them to size.