Re: [ATM] convex secondary

[Jonathan Lavoie <atm@lavoielactee.net>]

Vladimir, thank you for this interesting desing. If it was my first I would
go for it. But I'm modifying my current Gregorian because I'm not happy with
it's slow F18 ratio. I think I will stick to the F9 (or faster) RC. Then,
using focal reducer/barlow will give me good range...

Jonathan


----- Original Message ----- 
From: "vladimir sacek" <vlad@copper.net>
To: <atm@atmlist.net>
Sent: Wednesday, March 02, 2005 8:09 PM
Subject: Re: [ATM] convex secondary


> Heck, I messed it up again. I went with an f/2 primary, while the one at
> hand is f/3. Here's an aplantic 400mm f/11.45 Loweday with an f/3 primary:
>
> R1=-2400mm
> K1=-1.0353
> primary to secondary: -900mm
> R2=-630mm
> K2=-1.3632
>
> On best curved surface (r=500mm) field is diffraction limited at 30mm
> off-axis (nearly 0.4 degrees). More than can be used. On flat surface,
blur
> size 12mm off-axis is ~0.012mm - less than the Airy disc. The system is
> somewhat slower than f/9, but it is fairly compensated by
> better field quality and lower undersampling.
>
> Vlad
>
>
> > An example of a system that could be made with your mirrors is this
f/7.75
> > aplantic Loweday:
> >
> > R1=-1600mm
> > K1=-1.0372
> > distance to secondary: -600mm
> > R2=-413.333mm
> > K2=-1.2949
>
>
>
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