Re: [ATM] Flexing the Ubiquitous 4.5-inch Mirror

["Bill Kelley" <flex@commspeed.net>]

David,

If you  have made a "perfect" sphere, center pull will give you an optic 
better than 1/20th wave. If that is not good enough let me know and I'll 
suggest a simple ring pull flex cell that will do much better (?) In the 
real world it won't improve your images. Alan's "distributed load" flex 
scheme is needed for larger and faster mirrors.

One important way to reach best resolution is to reduce light scatter by 
making your mirror very smooth.

Bill Kelley

----- Original Message ----- 
From: "David Taft" <taftdb@yahoo.com>
To: <atm@atmlist.net>
Sent: Friday, June 24, 2005 4:35 PM
Subject: [ATM] Flexing the Ubiquitous 4.5-inch Mirror


> Hi,
>
> I am trying to decide if flexing a 4.5" mirror using Alan Adler's method 
> over Bill Kelley's original center-pull method will give me detectbly 
> better views at the eyepiece. Alan's method looks easy enough.  My only 
> real concern is it adds a bit of additional height to the mirror cell.  I 
> really don't have the option of moving the spider and focuser forward.  My 
> understanding is that if I did use Alan's method and went with aluminum 
> instead of polycarbonate, I can reduce the thickness of the plates by 
> something like one-third.  Is that right?  Anyway, here are the FLEX.EXE 
> inputs and SPOT RATIOs. Please let me know what you think.
>
> Thanks
>
> David Taft
> Manassas, VA
>
> "This is particularly true for the ubiquitous imported 4 1/2-inch 
> telescope mirrors...."
>
>
>
>     Alan Adler, S&T November 2000
>
>     "Flexing Spheres into High-Quality Telescope Mirrors"
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
> Unflexed Sphere:
>
>
>
> DIAMETER -------------------------------------------------> 4.5
>
> NUMBER ---------------------------------------------------> 8
>
> MIRROR-BLANK THICKNESS -----------------------------------> .64
>
> SECONDARY DIAMETER or 0=CALCULATE A GOOD SIZE ------------> 1.1
>
> PULLER BETA1 or 0=FIND BEST or 1=APPROXIMATE WITH RULE ---> 0
>
> PULLER BETA2 or 0=FIND BEST or 1=APPROXIMATE WITH RULE ---> 0
>
> BACK SHAPE SPEC (SEE NOTE BELOW) -------------------------> 1
>
> TAPER EXPONENT or 0=SPHERICAL BACK -----------------------> 1
>
> FLEX: 1=FIND FLEX   0=ANALYZE UNFLEXED SPHERE ------------> 0
>
>
>
> SPOT RATIO= .569
>
>
>
> Adler:
>
>
>
> FLEX: 1=FIND FLEX   0=ANALYZE UNFLEXED SPHERE ------------> 1
>
>
>
> SPOT RATIO= .008
>
>
>
> Kelley:
>
>
>
> PULLER BETA1 or 0=FIND BEST or 1=APPROXIMATE WITH RULE ---> .01
>
> PULLER BETA2 or 0=FIND BEST or 1=APPROXIMATE WITH RULE ---> .1
>
>
>
> SPOT RATIO= .173
>
>
>
>
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