Re: [ATM] 7 inch spherical mirror

["David Harbour" <stainless_steel@suddenlink.net>]

Bob,

I have read more than one author who said that if one attempts to make a 
corrector plate with the vacuum method for a system as fast, or faster then 
f/2, the plate will usually break.

R-101

Me, I would forgo the drudgery of a plate, and opt for some spherical 
abberation, with a slower, plateless camera. Sometimes I guess I am lazy. 
(Except when building my special tools to grind curve generated mirrors 
with, and building very large symmetrical equatorially mounted reflectors);

I offered to design a large (24") Ritchey Chretian, and supervise its 
construction, (the department head at one time wanted one)  for the local 
over- (way over-equipped) local little wheat town college, Northern Oklahoma 
College (usually referred to derisevely by the students as "No Other Choice" 
college); but they had already committed to a large ($80K) planetarium; the 
slab is poured, and they should have the geodesic dome components right 
away- the administration drew the line at spending on astronomy here 
(permanently, I think, as far as new equipment goes), so my last masterpiece 
of flame cut steel, beautiful machining, computerized drives, etc., will 
never be built. I asked for a little office in the astronomy sciences 
building (which by the way, bears a bronze plaque that says: "David Harbour 
Solar Observatory"- they rescued my two mirror polar heliost from the museum 
that had it gathering dust for 11 years; the head of the department is 
ecstatic at its performance (I was worried that it would work at all). There 
is a shiny STIANLESS STEEL tilt-off cover for it on the little building that 
can be seen at quite a distance. A lot of astronomy education going on here; 
surprising. The department head moved from Hawaii, of all places, and came 
to the land of red dirt and tumbleweeds, to do this thing. Said he had 
"Island fever" after 30 some years there.

I am told that several Universities have asked for detailed drawings and 
plans for my heliostat. I have pictures of it on my hard drive, if any wants 
some of them. My drawings, that I provided the machinist with, are long 
since gone. (12 years ago).

R-101


----- Original Message ----- 
From: "Bob May" <rmay@nethere.com>
To: <atm@atmlist.net>
Sent: Wednesday, April 16, 2008 12:01 AM
Subject: Re: [ATM] 7 inch spherical mirror


> Sheesh!!!  Now he tells me!  Been contemplating doing another
> corrector plate try for my 6"F1.95 sphere that I have.  Think
> that the better idea would be to put some of the correction on
> the mirror and some on the corrector afterwords.
> I'be broken two plates already trying to get this done.  The
> first broke sometime in the night but the second broke while I
> was present in the bathroom where I do my work at home.  An
> interesting little tink that came out of nowhere.  Guess that
> when you see bubbles coming out of the water underneath at a
> fairly rapid ratee, you have too much vacuum!
> Bob May
>
> rmay at nethere.com
> http: slash /nav.to slash bobmay
> http: slash /bobmay dot astronomy.net
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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