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[ATM] Tri-schiefspiegler-- update
Work continues on the Trischiefspiegler (Kutter). I still feel a bit blind in building this, but thought I distribute some of the Winspot files. I couldn't get the TM-16 design to come in quite like I thought it should so stretched and tweaked it to f/15. Apologies to Mr. Kutter as I am sure the design is not optimal, but was about as good as I could get with Winspot's help. Great little program BTW, thank you David Stevick.
Of note, the Rutten and van Venrooij design is quite good (after adjusting the mirror angles). Much better than presented in the book. If mine wasn't planned as a star-party scope (portable) think I would have built the longer version.
I'm just putting the finishing touches (I hope) on the mirror from hell... the tertiary, but not for the normal reasons. Just as I was dialing in the FL it hopped off the machine and found the concrete floor-- lots of little tertiaries :-( Got the new blanks which took 3 hours with #60 to get flat (for a sag of .0013"). Then, in and when washing off the grit the mirror and the tool touched, yup a chip. Later, the tool and mirror grabbed and guess I was a bit heavy handed, another chip. I haven't chipped a mirror in 5 years, now 2 on the same one. The diamond file smoothed things up and I'm using a 4" blank for a 3" mirror so will be fine, but... Guess we all have these once in a while.
There is some good news. Tested the Tertiary last night and may have a strategy that makes it easy. I use a laser diode as the source on my Foucault tester (also have a green LED slit).
Normally-- With the collimating lens in place (laser pointer beam) the tester is very easy to set up: adjust the tester to laze the center of the mirror and adjust the mirror to return the beam where desired on the tester. Then remove the lens and adjust the series potentiometer so the diode is not lazing and test (very small "pin-hole).
With the long FL of the tertiary I found I couldn't see the image of the non-lazing diode so left it at full brightness, but without the lens. Still need a finder scope to see the mirror and there are some interference effects but seemed to work well. The main laser effect were some bright rings centered on the mirror (may actually be of use) and in a junk finder some speckles. Need a bit more testing to verify effectiveness but looks promising. The holder for the mirror is attached to a "slow motion" pan tilt head, so even at 80' it's easy to point.
If anyone knows how to calculate the curves and angles of the trischiefspiegler, feel free to kabitz... or if you know of a calculator...
Thanks,
____________f/15, 6" (the one I'm building)______________
WinSpot V0.93b Tri-schik-6c
3 surface design
Type Radius CC/Rsag Tilt Separation
0 3129.99 0.53 5.1 781
0 -4588.8 0 -15.299 486.1
0 25324 0 -35.215 667.1874
0 0 0 8.726035 focal plane
Aperture 150 mm Field 0.2 Degrees f/15.02
____________ f/19.4 Rutten and van Venrooij _______________
WinSpot V0.93b Tri-schi6-RV
3 surface design
Type Radius CC/Rsag Tilt Separation
0 4065 0.53 5.117 1012.5
0 -5950.25 0 -15.21 645
0 32735 0 -34.99 858.914
0 0 0 8.698577 focal plane
Aperture 150 mm Field 0.2 Degrees f/19.54
____________Telescope making #16 Al Woods_____________
WinSpot V0.93b Tri-schif-6alwood
3 surface design
Type Radius CC/Rsag Tilt Separation
0 3097.53 0.53 5.178 771.65
0 -4520.94 0 -15.4 467.36
0 24950.42 0 -34.7 671.976
0 0 0 8.77805 focal plane
Aperture 150 mm Field 0.2 Degrees f/14.88
______________________________________________________
Greg Jones
http://home.comcast.net/~dac20/dac_001.htm
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