Re: ATM Schiefspieglers in Oslo LT

["Good, Donald" <dgood@aha.org>]

I also became interested in the unobstructed reflector and began
investigating the
schiefspiegler designs.  (Is schiefspiegler synonymous with TCT?)  This led
me to
David Stevick's Weird Telescopes:
http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/weird.htm
and the Stevick-Paul telescope (SPT):
http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/sptbrief.htm

I downloaded the latest OSLO LT (now OSLO EDU v6.2.2) from
http://www.sinopt.com/
and put in the numbers for David's 8" SPT.  I got tired of trying to tweak
the
numbers into OSLO form, so I made an Excel spreadsheet with David's
equations and
conversions to the OSLO parameters. (David, may I post the spreadsheet to
the 
ATM list?  Reply off-list)

********* YOU HAVE GOT TO SEE THIS IN OSLO ****************
If I am interpreting this right, NO coma, NO spherical aberration, NO
chromatic
aberration, NO obstruction, spot size smaller than 1/10th of airy disk
across
whole (.2 degree) field, STREHL RATIO 0.999643
Here is the SPT8.len file.  Is my interpretation right?

// **** START OF FILE - copy and paste starting at next line
// OSLO 6.2 20216     0 10427
LEN NEW "STEVICK-PAUL 8" -93.603 4
EBR  4.0
ANG  0.2
DES  "OSLO"
UNI  25.4
// SRF 0
AIR 
TH   1.0e+20
AP  3.4906726816e+17
NXT  // SRF 1
RFH 
RD   -188.0
TH   -56.32
CC   -1.0
DT   1
TLA  3.04
NXT  // SRF 2
RFH 
RD   -75.2
TH   74.88
AP  1.79
DT   1
DCY  -2.99
TLA  -2.28
NXT  // SRF 3
RFH 
RD   -75.2
AP  2.41
DT   1
DCY  -6.96
TLA  -7.59
NXT  // SRF 4
AIR 
TH   -37.3874211807247
DT   1
TLA  7.0
CBK  1
WV 0.58756 0.48613 0.65627
WW 1.0 1.0 1.0
END  4
DLID 60.0
DLRS 3
SDSA On
// *** END OF FILE - do not copy this line

For those without OSLO, I could send the graphics analysis images somewhere
to
be posted, but where?  Maybe to www.atmsite.org where Steve Fejes' OSLO
intro
is hosted? 


-----Original Message-----
From: Mark Holm [mailto:mdholm@telerama.com]
Sent: Wednesday, March 12, 2003 7:50 PM
To: atm@shore.net
Subject: ATM Schiefspieglers in Oslo LT

I am wondering if anybody has done setups for schiefspiegler designs in Oslo
LT.
   I am rather ignorant about Oslo LT and am not sure how to go about the
setup.
   I would like to start with the small 2-mirror designs, and then proceed
to the
larger designs with corrector lenses.

I note that a German ATM has designed an improved schiefspiegler with two
meniscus lenses as the astigmatism corrector. 
http://www.videoastronomy.org/schiefspiegler/kutter.htm  He indicates that
the 
correction
of aberrations is better across the field of view, and that the field tilt
has
been eliminated.  The only problem is that he says he is not releasing
design
details because he wishes to patent the design.  I'm not at all sure a
double
lens design is in my future, since I have never made any type of lens.  I am
still interested in analyzing schiefspiegler designs with modern software.

Mark Holm
mdholm@telerama.com