Xref: utzoo sci.astro:8477 sci.space.shuttle:5872
Path: utzoo!utgpu!watserv1!watmath!att!tut.cis.ohio-state.edu!cs.utexas.edu!sdd.hp.com!decwrl!shelby!helens!news
From: news@helens.Stanford.EDU (news)
Newsgroups: sci.astro,sci.space.shuttle
Subject: Re: The end of Hubble
Message-ID: <818@helens.Stanford.EDU>
Date: 23 Jul 90 08:01:56 GMT
References: <1990Jul20.073745.28245@portia.Stanford.EDU> <8043@ncar.ucar.edu> <1990Jul22.110035.1194@uoft02.utoledo.edu>
Sender: news@helens.Stanford.EDU
Followup-To: sci.astro
Distribution: na
Organization: Stanford University, Department of Geophysics
Lines: 27


	I have a simple question: when Amateurs grind a mirror of their
own (say 8") they use the "knife edge" test to look for aberrations.

	I suspect the "knife edge" test would not be good enough to catch
the minuscule sorts of errors they were EXPECTING in Hubble's primary. BUT...

I'm very curious to have 3 questions answered:

1) How hard/expensive would the "knife edge" test have been to do on Hubble's
	primary?

2) Would it have caught the more gross spherical aberration suspected?

3) If the answer to (1) is "not very expensive" and to (2) is "yes it
	would have caught the spherical aberration", why wasn't the test
	done as a simple sanity check?



	Well, I guess now Celestron will be able to advertise "our
telescopes' mirrors are guaranteed more accurate than the mirror in
the Space Telescope!".
\    /\    /\    /\/\/\/\/\/\/\.-.-.-.-.......___________
 \  /  \  /  \  /Dept of Geophysics, Stanford University \/\/\.-.-....___
  \/    \/    \/Joe Dellinger joe@hanauma.stanford.edu  apple!hanauma!joe\/\.-._
************** Hello, Comrade! *************************************************