[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: [ATM] RC design

At 2005-03-23 22:48 -0500, Jonathan Lavoie wrote:

>I'm now fixing the numbers for my Ritchey-Chretien design.
>406.40  Primary Diameter
>107.00  Secondary Diameter
>1016.00  Primary Focal Length
>3861.06  Effective Focal Length (EFL)
>800.87  Primary to Secondary distance (d)
>817.56  Secondary to Image Plane distance (s')
>583.92  Secondary RoC

At 2005-03-24 23:51 +0000, Richard wrote:

>Conic
>-1.03724
>-3.37777

I agree with Richard's conic constants.  So the surfaces' prescriptions are

                 R       b
primary 2032    -1.03724
secondary       583.92  -3.37777

corresponding to the design parameters (d, s', EFL) = (800.87, 817.56, 
3861.06).

Just for fun, suppose, during the figuring phase, the primary is exact, but 
the secondary's R = 583.0 mm (off by .9 mm).  Is it good enough?  The 
answer is yes, the system's wavefront RMS is 20.8 nm (passing is 40), 
relative to the altered design parameters (800.71, 823.40, 3885.72).

You'll need an alternative to testing the f/2.5 primary with Foucault 
during figuring.  I'll push my 2D Hartmann test.  For a usual webcam, that 
would require a mask with 250 square holes, but it ends up being equivalent 
to a Foucault test with 500 holes <g>.

         -- Jim Burrows
         -- mailto://burrjaw@earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84) 

_______________________________________________
ATM mailing list http://www.atmlist.net/