Re: [ATM] The 15.5 Ultrathin Project, Astigmatism discussion

[Dale Eason <atmpob@yahoo.com>]

Not really.  The flat will introduce its errors into
the measurement.  A household mirror's error will
swamp any error on the mirror.  One technique for
measure a diagonal is to put it into the path when
measuring a sphere (the center of most parabolic
mirrors is a close approximation to a sphere.) Go
ahead and try it when you get home you should see hugh
errors.

Dale Eason

--- GARY FUCHS <gary@rcn.com> wrote:

> Could you use a flat (maybe even a common household
> mirror 
> for a rough view?) to cut the height down to a
> manageable 
> amount? I may try this when I get home.
> 
> Gary Fuchs
> 
> ---- Original message ----
> >Date: Fri, 20 Jan 2006 20:06:27 +0100
> >From: "Vladimir Galogaza"
> <vladimir.galogaza@zg.htnet.hr> 
> >Subject: Re: [ATM] The 15.5 Ultrathin Project,
> Astigmatism 
> discussion  
> >To: "ATM List" <atm@atmlist.net>
> >
> >Hi David,
> >
> >>I normally support the mirror's edge
> >>with two  points at the bottom, but I will
> experiment with a 
> strap.
> >
> >What do you expect. If stand induced astig is what
> is seen, 
> than strap
> >can not remove it, perhaps modify but not remove,
> because 
> the situation
> >is basically not changed by sling usage.
> >It will be changed by testing the mirror as
> recommended by 
> Gary
> >>Could you test from above with the mirror lying
> flat?
> >But your mirror is 15.5 inch f/6 that means you
> will need 5 
> meters
> >of space for test, right. I hope you will manage
> this because 
> what
> >you are doing is very interesting and I cant
> remember it was 
> ever done
> >in this way AND reported to the list.
> >
> >Regards
> >Vladimir.
> >
> >
> >
> >
> >-- 
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