Re: [ATM] World's First Ritchey Chretien reflector (.5 meter)

["David Harbour" <scarab2@cox.net>]

Yes I do, John!

I will send it to you in just a  few seconds. It is an historic photograph;
among other things, and it shows very obviously the very same "kinematic"
method (though used on only the north end) of how I carry my polar axles on
my large instruments. Look for it right away-

Dave

P.S. After you get it, go to:

http://www.atmsite.org/contrib/Harbour/Brngz.html

and read how this system works- it's neat- five little bearings instead of
two colossal (and colosally expensive) bearings. Works like a dream.

Although Ritchey and Chretien used kinematic support for their polar axle on
the 20" RC, they may not have used it for the other five contact points, as
I always did. (Southg end, three bearings; that way the entire polar axle
slipped out easily by one person. My version of a "Dobbie" whose altitude
axis just happens, through that little miracle, a "polar" axis (no field
rotation, no blind spot qat zenith, room for accessories, etc.)

Look for snapshot right away, John-

Dave

P.P.s.- It turned out to be available only on the other machine as a 5.5
megabyte Tif, so I fixed that (about an hour's job to find it, and make the
old machine do what I wanted it to do) but I've copied it to this machine,
and in a New York minute willl send it. You will find it elegant,
foreshadowing the future. Original caption from Osterbrock's book retained.
My old machine gave me some resistance to my simple routine to resize (I use
Word and save as web page; pretty neat). Darned thing wanted me to jump
through file naming hoops I never saw before; but these machines, bright as
they are, are GULLLIBLE. Picture on its way.




----- Original Message ----- 
From: "John Lynch" <john_lynch2005@yahoo.com>
To: "David Harbour" <scarab2@cox.net>
Sent: Wednesday, June 08, 2005 9:14 AM
Subject: Re: [ATM] mirror damage


> David,
>
> If you have the picture available electronically,
> could
> you email me a copy?
>
> Thanks.
>
> John Lynch
>
> --- David Harbour <scarab2@cox.net> wrote:
>
> >
> > To Guy, and all:
> >
> > Ritchey (Gee Dubbya) used to tell his underlings to
> > be very careful when
> > working the 100" Hooker mirror, because it was
> > "liable to detonate (explode)
> > at any time".
> >
> > Ritchey was a "practical Joker". Once, he let
> > Chretien guide a very long
> > exposure (I think with the brand new prototype of
> > the Ritchey Chretien
> > reflector, a 20" instrument), only to inform him at
> > the end of the exposure
> > run (man, many hours) that the film shield plate had
> > never been removed! I
> > think I might have, if I were Chretien, have applied
> > a hammer to his
> > forehead.
> >
> > BTW, this instrument carried its polar axle the same
> > way I carry mine, in a
> > standard design. If anyone would like a copy of this
> > picture of the very
> > elegant first 20" Ritchery Chretien reflector, just
> > ask. I think both of the
> > great men are in the picture.
> >
> > Dave
> >
> > ----- Original Message ----- 
> > From: "Guy Brandenburg" <gfbrandenburg@yahoo.com>
> > To: "Cec & Cris" <ccabar@bigpond.com>;
> > <atm@atmlist.net>
> > Sent: Monday, June 06, 2005 7:03 PM
> > Subject: Re: [ATM] mirror damage
> >
> >
> > > Ignore it, mostly. Use a coarse sharpening stone
> > to
> > > file the area down somewhat so that the area won't
> > > chip any more. Do NOT add glue or fiberglass or
> > > anything like that. The aluminizer will REALLY not
> > > like having stuff like that outgassing inside the
> > > vacuum chamber. It could actually explode.
> > > Guy B
> > >
> > > --- Cec & Cris <ccabar@bigpond.com> wrote:
> > >
> > > > Hi guys
> > > >
> > > > I need some advise. I have come across a problem
> > > > grinding my pyrex 250mm mirror. I was grinding
> > with
> > > > the 240 grit (mirror on top) when a chip came
> > off
> > > > the side (edge). It only slightly affected the
> > > > circular shape < 1 mm. The problem is that it is
> > a
> > > > rather large chip and it has not left much
> > thickness
> > > > at the top edge about 1mm. Can someone advise me
> > on
> > > > what I should do? I was thinking of filling it
> > up
> > > > with fibreglass filler (builders bog) to
> > strengthen
> > > > the edge a bit so that I can continue grinding.
> > Can
> > > > I do this or will this have an affect on the
> > > > illuminisation? Will it come off or melt? Is the
> > > > illuminisation done with heat or not? Can
> > someone
> > > > please advise.
> > > >
> > > > Regards Cristian
> > > > _______________________________________________
> > > > ATM mailing list http://www.atmlist.net/
> > > >
> > >
> > >
> > > Guy  Brandenburg
> > > Washington, DC
> > > My home page:
> > >
> >
> http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
> > > _______________________________________________
> > > ATM mailing list http://www.atmlist.net/
> > >
> >
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
>
>
>
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