From: "Thomas Janstrom" 
To: "David Margrave" 
Cc: "atm" 
Reply-To: "Thomas Janstrom" 


Dave, I can send you a 0.001" by 1" spindle custom made for a
sphereometer for $10 +postage.

I use a meteric version in my 4" sphereometer and I can produce optics
(three seperate mirror with ROCs varying, by less than 1" over 30') as
close to identical as you could expect from hand pushed glass.

You can see the sphereometer I built at www.tjanstrom.com\spherometer.html

Clear skies, Thomas
http://www.tjanstrom.com
"Don't make me set the laser printer to stun"

----- Original Message -----
From: "David Margrave" 
To: 
Sent: Friday, January 24, 2003 9:37 AM Subject: ATM 8" refractor project


>
>
> Hello,
>
> I'm going to be particpating in the 8" refractor class at the western
> washington university telescope optics workshop.  I want to prepare a few
> things in advance: spherometer and wedge tester.
>
> For the spherometer, there seems to be a lot of talk back and forth about
> what is suitable for a dial indicator/micrometer.  Some people have said
> that the cheap .001" dial indicator is fine.  Others say that you need
> .0001", which would require either a micrometer spindle, dial test
> indicator, or precision dial indicator.  I have found .0001" dial
> indicators with very limited travel, .0005" with suitable travel, and of
> course the standard cheap .001", but nothing of the sort that Roger
> Ceragioli calls for in his instructions: .0001" with 1/4"
travel.  Is it
> simpler to just take a hacksaw to a micrometer to salvage the spindle?
>
> What size base should I be making for working on an 8" lens?  I'd guess
> 5-6".  I have access to a machine shop which I'll make use of for this
> project.   Should I try to make a fancy base with multiple tapped holes
> for the feet, or just keep it simple and permanently fasten the feet.
> I've seen some plans for adjustable spherometers of this sort which seem
> interesting.
>
> For the wedge tester, I think I've got the general idea.  I'm going to
> take a sheet of melamine (laminated particle board), and put in some
> threaded inserts for holding the feet and the stops, and for the dial
> indicator post.    No need for metal or high precision in the construction
> of a wedge tester, right?
>
> I have an idea for a relatively simple do-it-yourself optical tube: with a
> router cut some rings out of aluminum plate, take a sheet of aluminum and
> run it through a slip roll, put a 'step' on one edge to make for a
> prettier seam, and then screw or rivet the skin to the frame of rings.  I
> don't have the background to make the design decisions however (how many
> rings, how thick a skin, etc).  For the lens I'll be working oon, I think
> I'm looking at a 10' tube, so I may build it in two or three sections
> which can be bolted together.  I'm also seeking information on lens cell
> design.
>
> Thanks,
>
> Dave
>
>
>

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