Re: [ATM] convex secondary

[Jonathan Lavoie <atm@lavoielactee.net>]

Richard, please ignore this last post. I tought you were speaking about the
terciary being 4.12", not the secondary!

----- Original Message ----- 
From: "Jonathan Lavoie" <atm@lavoielactee.net>
To: <atm@atmlist.net>
Sent: Tuesday, March 01, 2005 12:19 PM
Subject: Re: [ATM] convex secondary


>
> ----- Original Message ----- 
> From: "Richard" <cnc@cncservo.co.uk>
> To: "Jonathan Lavoie" <atm@atmlist.net>
> Sent: Tuesday, March 01, 2005 11:59 AM
> Subject: Re[2]: [ATM] convex secondary
>
>
> > Hi Jonathan,
> >
> > Tuesday, March 1, 2005, 4:15:28 PM, you wrote:
> >
> > JL> Why wouldn't the secondary be 4", I tought the only difference
between
> > JL> Cassgrain and RC was the figure of both primary and secondary
mirrors?
> >
> > If you are still using your tertiary diagonal mirror and can get
> > away with the -2" back focal length, then to cover field of your
> > camera sensor the secondary needs to be 4.12" diameter.
>
> Are you sure? Even is the on-axis lignt cone is less then 2" ? (The
terciary
> located at 19" from primary surface or 17" from the focal plane)
>
>

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