Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1572
Loc: Fort Worth TX
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Ed, that's a great f/12 design. I keyed your prescrip in and got the layout and ZEMAX full-field spot plot shown, with Airy ring indicated at center. The outer circle is plotted exactly 2" in diameter, but the spots and Airy ring are plotted 200X larger than they really are. Very good performance over the field.
Mike
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1572
Loc: Fort Worth TX
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HOWEVER, going tilted and unobstructed for my 16" f/6 primary doesn't come out "quite" so good (like nowhere near). This first design uses a long-radius conic secondary similar to Ed's, and N-LLF6/N-BK10 correctors. The spots are huge.
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1572
Loc: Fort Worth TX
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Tried something a little unusual - an all-spherical wedged Mangin mirror. The refractive front and reflective rear surfaces are tilted to each other by 1.67 deg., the thicker side below. The Mangin is Ohara S-FPL51, and the correctors are Ohara S-TIM22 and Schott N-LaK21. That did help get the spots down smaller as you can see, especially the on-axis spot. But still a long way from Ed's nice pointy images over the FOV.
I'm going to continue to mess with it - I love the idea of no central obstruction, but the imagery without it has to be of high enough quality to be worth the trouble to build, which these designs are not. A 16" f/6 is just a really hard mirror to make unobstructed.
Mike
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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ED how much better is this than if you used a flat . THANKS for all the cool telescopes .
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3121
Loc: Northeast
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"This corrects the image tilt and with a hyperbolic primary eliminates coma. "
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Have been thinking about the secondary, and these aspects. If it corrected for the image tilt, there wouldn't need to be a pair of lenses, correct?
The hyperboloidal mirrors correct for just coma, like an RC "on axis" scope???
Just trying to let my mind grasp all the aspects of this design.....
==========================================
I've got a "what if" idea. The primary is about F/6. Let the light come to focus, and allow the secondary to be concave, located maybe 120-130" away from the primary, with a fairly low primary tilt. The secondary tilt bounces the light to the side below the primary, with a pair of lenses to cancel out the tilt abberations. (something like an off axis Gregorian)
Something tells me that the image tilt could be messed up, but perhaps it might be worth looking at???? 
Mark
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So many projects, so little time!
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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I tried to make it faster to answer Marks question, I think it is still OK at f/9.8. At f/8.2 the spots at .25 deg off axis are a half again larger than the airy disk size. That's with a f/7.1 primary. It's hard to go much faster because of the secondary amplification. Using more exotic glass in the correctors can improve the spots a bit but fused quartz lenses is nearly as effective and probably a lot less expensive. I used it in these faster designs.
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Ed Jones
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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why is mark and mark trying to have ED CHANGE THE PERFECT TELESCOPE HOW MUCH MORE DO WE NEED . LETS GET BUILDING AND GO WITH IT AS IS.. MIKE JONES SAYS IT IS VERY GOOD . THAT IS GOOD ENOUGH FOR ME .THANKS ED
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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I know they wonder about doing it different ways . i have ask Ed hours of question and in the end his way is the way to go .. he has it all figured out.just build it buy the numbers! not much diferent than a newtonian! . a f10 mirror is harder than a f5 but not much more .not sure on the secondary
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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There is not a lot of coma in an f/10 Chief especially compared to a faster Dob. You'ld have to weigh the benefits in performance to the extra work of making the hyperbolic secondary versus the regular Chief.
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Ed Jones
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2158
Loc: salem, OR
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Kevin,  Change the perfect telescope?? There is no perfect telescope! Ah, except the one you own, of course. 
What I'm curious about (ever since Ed mentioned the shorter design work) is where the design could go for production optics, that's all. Wider fields, shorter OTAs, "exotic" elements all have appeal commercially. Nobody says anybody has to deviate from what they like, I'm just a curious sort. Like what Mark H. says:
Quote:
Just trying to let my mind grasp all the aspects of this design.....
Ed, transmission quartz at .8" thick is available (by picking it out from blanks) in small quantities to 14.7" diam, is this adequate? Around f/8 on the 16"? What about smaller, down in the 8-10" size? IIRC it scales faster smaller, or is that just my averted imagination??
Best,
Mark
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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That quartz is plenty big enough, the lenses are only about 4 inches and thickness isn't very important. Primary is f/8.4. Here's the design.
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Ed Jones
Edited by Ed Jones (11/04/09 07:01 PM)
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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MARK I KNOW I ASK ED THINGS ALL THE TIME .ALOT OF WAYS TO BUILD A CHIEF ..ED CAN MAKE A OFFAXIS WORK UP TO 50 INCHES .PRICE OF A 16 INCH PYREX 1 5/8 INCHES THICK PREGENTERATED BLANK IS 625 . DOLLARS.
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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hi MARK C YOU COULD GET A TEST PLATE/ SECONDARY MIRROR/ AND TWO LENS OUT OF ONE 14.7 INCH QUARTZ BLANK.. I THINK.. ALL QUARTZ OPTICS. MAYBE A 14.7 INCH PRIMARY
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2158
Loc: salem, OR
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Thanks, I think you're right. Some of the plates have no bubbles and are refractive grade, most of them have bubbles and aren't refractive grade. I've tested a few that could make lenses and I can get some more. I like the all-quartz approach.
Best,
Mark
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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yes that sounds great[QUARTZ OPTICS]. great optical design. great optics . a ultralight mount!! sounds like a goode
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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Forgot to change the glass type from BK7 to silica on that last design. It is fused quartz not BK7 (I must have CRS). 
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Ed Jones
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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CRS??
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1572
Loc: Fort Worth TX
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Can't Remember "Stuff" (ya have to say "stuff" to not violate TOS and get bleeped) 
Mike
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 662
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I THOUGHT MAYBE CHIEF REFLECTOR SICKNESS
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marcething
member
Reged: 04/20/06
Posts: 19
Loc: Lint , Belgium , Europe
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Hi Ed ,
Is the CHiefspiegler with no CA, no coma, no image tilt, no obstruction,no Sherical aberartion ... possible at F/8 for a 10 or 12" , and could you please calculate this ?
Thanks in advance
Marc
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