Re: [ATM] Another Astigmatism question, but at the sphere stage

[Jarvis Krumbein <jkoptic@juno.com>]

Hi Jerry,

The problem is not that great.  John Strong in "Proceedures in
Experimental Physics" has a couple of rotatable knife edge arrangments
(fig. 32 in the chapter on Laboratory Optical Work).  Also, there is a
good 5 page article on testing for astigmatism by Warner in "Amateur
Telescope Making _ Advanced".  The article starts on page 70 of my 1937
edition and I assume that it's included in the Willmann-Bell reprints.

Jarvis Krumbein <jkoptic@juno.com>

On Sun, 28 Aug 2005 14:59:44 -0400 Royston_Jeremy@emc.com writes:
> Hello Jarvis,
> 	The knife edge to mirror distance should be kept constant to 
> better
> than your measurement accuracy while rotating it - say 0.001" or 25 
> micron.
> This isn't a trivial mechanical problem. The ball bearing test 
> described in
> Texereau isn't quantitative, but very sensitive. Perhaps on of the 
> more
> mathematically inclined members could supply a simulation rather 
> like
> Diffraction
> 
> Best wishes, Jerry
> 
> -----Original Message-----
> From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On 
> Behalf Of
> Jarvis Krumbein
> Sent: Sonntag, 28. August 2005 20:35
> To: wa4guu@verizon.net
> Cc: atm@atmlist.net
> Subject: Re: [ATM] Another Astigmatism question, but at the sphere 
> stage
> 
> Instead of going to the trouble of rotating the mirror why not 
> rotate the
> knife edge/slit to achieve the same end.  It would be much easier to
> compare readings taken across different diameters and would give 
> instant
> answers.
> 
> Jarvis Krumbein
> 
> On Sun, 28 Aug 2005 13:09:41 -0400 "Jerry" <wa4guu@verizon.net> 
> writes:
> > I did not reply because I don't know if Jay's test method is valid 
> or 
> > not. I
> > think it is flawed but since I know little about Sixtests, the 
> order 
> > and
> > timing of his 3 sets of readings on 2 diameters and how he chooses 
> 
> > those
> > diameters I think it is too difficult to offer help by email. So 
> not 
> > knowing
> > I thought I should stay out of it.
> > 
> > But.....
> > 
> 
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> 

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