Re: [ATM] Another flat-field anastigmatic aplant

["Ukyo Chen" <ukyochen888@hotmail.com>]

----------Original design-------------
A design of powerful and fast 3 mirrors reflecting telescope
http://www.astron.sh.cn/cgi-bin/attachment.cgi?forum=2&topic=1617&postno=1&type=.gif

Mirror 1 is the major paraboloid with contain coma
Mirror 2 is a spherical surface which will introduce spherical aberration to 
the system, but no coma.
Mirror 3 is an ellipsoidal surface that can correct spherical aberration and 
coma, but the field is curved
Mirror 4 is just a flat mirror like Newtonian telescope's secondary mirror, 
to give convenience for eyes.
Lens 1 smooth the curved field for eyepiece or photo.

Strongpoints:
1.It has a F/3 fast speed;
2.A large excellent image field, 60mm diameter,or 4.6 degree, with little 
chromatic aberration;
3.easy to grind. mirror 1 is a concave paraboloid, mirror 3 is a concave 
ellipsoid, both of them can be tested using a knift edge+SIXTEST program, 
mirror 2 is a convex sphere so that it can be tested while mirror is still a 
sphere, using "Newton's circlet"

Here are shortcomings:
1. semi illumination
2. very difficult to adjust axis
3. obstruction area is 21.8%, just acceptable
4. need to make some change(as it is not long enough from the lens 1 to the 
focus, or negative) when photo on the focus without eyepiece,can't use 
barlow too.

References:
http://www.ast.cam.ac.uk/history/mmmt/
----------------------



----------improved design------------
I have done a modification again
1.no lens, no chromatic aberration
2.improve the speed to F/2.67, very fast now!
3. No more need to make some change when photo on the focus without eyepiece 
since no lens on the way to focus,can use barlow too.
4.The tube length is only 420mm now, much shorter than 750mm before
5. smoothly enhanced illumination

Others
Now there is a hyperboloid, a concave ellipsoidal surface and a convex 
ellipsoidal surface need to be done.
--------------------

Best Regards,
Ukyo Chen

>From: "Richard F.L.R. Snashall" <rflrs@rcn.com>
>To: atm@atmlist.net
>Subject: Re: [ATM] Another flat-field anastigmatic aplant
>Date: Sun, 18 Dec 2005 21:15:49 -0500
>
>Ukyo Chen wrote:
>
> > The whole post link is:
> > 
>http://www.astron.sh.cn/cgi-bin/topic.cgi?forum=2&topic=1617&start=0&show=0&man=
> >
> >
> > Please scroll down to post number 10 as it is the improved version.
>
>I couldn't find the prescription on that page either.  Could you post it?
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