Re: [ATM] starting grit size

["Greg Jones" <gregj888@comcast.net>]

Jonathan,

I'm sure I am coming into this late, but why are you grinding at all?
Assuming a classical Gregorian you need very little figuring to change the
parabola to the Hyperboloid of the RC, just a pitch lap.

If you have too grind, I would probably start with 120/220 grit... but then
again I would be hard pressed to grind at all.  If the issue is design, send
me the ROC of your current primary and your final desired effective focal
length and I can give you a starting point.

As an aside, the Gregorian, Newtonian and Cassegrain describe mirror
configurations; RC, Classical and Dall-Kirkham specify the figure of the
mirrors.  A "normal" RC is a Cassegrain, a "normal" (classical) Gregorian
has a parabolic Primary.  There is an RC flavored Gregorian...

Greg Jones


>
> Message: 4
> Date: Fri, 15 Apr 2005 16:18:11 -0400
> From: "Jonathan Lavoie" <atm@lavoielactee.net>
> Subject: [ATM] starting grit size
> To: <atm@atmlist.net>
> Message-ID: <006901c541f8$3ed68c30$fc1414ac@mdebug.int>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hello,
>
> I will begin soon the regrinding of my 16 inch to convert it from a
gregorian to a Ritchey-Chrétien. The primary is around F3 and I have just
minor modification to do. I poured my cement tool and will glue 1" tiles on
it.
>
> So at which grit size do you recommend to start grinding to make the tool
match the mirror then remove around 0.3mm of glass?
>
> Jonathan
>
>

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