[ATM] more on cassegrain baffling...

["Benoit Schillings" <benoit.schillings@openwave.com>]

Hello List,
 
I am in the process of designing the baffling for my 16 inch F/12
cassegrain and after
using Michael Peck great spreadsheet, I was wondering if there would be
some approches
to baffling that would help me maintain a pretty good fully illuminated
field and shielding
without increasing dramatically the central obstruction caused by the
secondary baffle.
 
I was looking at the SDSS (Sloan sky survey scope) and noticed that they
used a 3 elements
baffle (primary, secondary + a between primary/secondary baffle) in
order to have both large
field and small obstruction.
 
Does anybody on the list knows about this, this sounds like a very
intriguing approche but
do not know the theory behind it.
 
for reference, my current design is
 
16 inch primary F/3.5
3.4x secondary mirror, D = 4.5 inches
41 inches mirror spacing
 
Currently, to have a fully shielded/illuminated field, the central
obstruction goes
to 0.31 for a 10 arcmin field... I would like to increase the usable
field to 20 arcmin
but do not like what it does to central obstruction (goes up to 0.34)
 
 
-- benoit
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