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Ajohn
sage
Reged: 12/03/07
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A corrected design for USP4881801?
#5643081 - 01/25/13 06:13 PM Attachment (54 downloads)
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I came across some references to a type of telescope with a positive power corrector and a spherical mirror and found the patent for it. It's referred to as the Gebelein Telescope. It sounds interesting from the claims in the patent but the design it quotes figures for doesn't work to well at all - The patent does seem a bit mixed up in places.
I've had a play with it in oslo and have attached a file but what ever my simple mind can do doesn't cause it to live up to the claims. It should produce an F5 flat field 8in newtonian style scope via a spherical mirror and 2 small simple lenses made out of the same glass! AND lower aberrations at increased field angles!
John
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Loc: Fort Worth TX
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Re: A corrected design for USP4881801?
[Re: Ajohn]
#5643226 - 01/25/13 07:40 PM
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Yep, pretty underwhelming! Loads 'o' coma.
Mike
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Ajohn
sage
Reged: 12/03/07
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Re: A corrected design for USP4881801?
[Re: Mike I. Jones]
#5643846 - 01/26/13 06:29 AM
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The figures in the oslo file are one interpretation of the patent. I've played with spacings and it's not possible to get the F ratio and focal length to tie in with the figures it gives at the same time. Oddly the Petzval curvature comes out as stated.
Problem for me is that there are too many variables for edu sliders to sort out and I have never been able to get my head round adding aberrations so have no way of getting at the basic idea.  I was sort of hoping some one with more ability in this area might give it a go. It seems to have a lot to offer over a straight newtonian without much in the way of extra glass. Spherical mirror, flat field and reduced aberration. Even a reduction in the F ratio of the mirror.
John
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MKV
Carpal Tunnel
Reged: 01/20/11
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Re: A corrected design for USP4881801?
[Re: Ajohn]
#5643935 - 01/26/13 08:20 AM Attachment (12 downloads)
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The Petzval curvature is simply the total of all the curvatures and refractive indices in a given configuration. By curvature (c) I mean inverse radius of curvature (R), i.e. c = 1/R.
As for this patent, I don't think there is an optimized solution. You can, however, correct a simple spherical mirror on axis with a single meniscus lens.
Here is a 200 mm f/8 configuration, covering about 0.3 degrees (or about 9 mm).
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polaraligned
professor emeritus
Reged: 12/26/08
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Re: A corrected design for USP4881801?
[Re: MKV]
#5644092 - 01/26/13 10:15 AM
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I am continually amazed what people waste their money patenting.
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ed_turco
Pooh-Bah
Reged: 08/29/09
Loc: Lincoln, RI
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Re: A corrected design for USP4881801?
[Re: polaraligned]
#5644111 - 01/26/13 10:26 AM
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I am even more amazed that the patent office let this squeak through.
I tried for an optical design patent and the examiner nailed me on too many points and I was justifiably turned down. 
I was 16 at the time, and I won't talk about my piddling little design.
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Ajohn
sage
Reged: 12/03/07
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Re: A corrected design for USP4881801?
[Re: ed_turco]
#5644171 - 01/26/13 10:59 AM
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I wonder if the numbers he quotes are for a thin lens design. It seems the scope was sold in the past. There is mention of it in these forums.
The single lens corrector is interesting. There is a paper by Maksutov on a meniscus ahead of the focal plain as well as the normal form. No luck in obtaining it though. Only a part copy that doesn't cover that aspect. It can be bought of course.
Patents are curious things. I held a number via my job some in all major countries but I remember one that never made it into the USA as loads of completely unrelated patents were thrown against it. I suspect this can be a bit of a nationalistic thing or down to how the person who examines it feels on the day. In this case the patent may have got through because of the mention of a positive power corrector.  If he had said focal reducer he might not have got away with it.
John
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polaraligned
professor emeritus
Reged: 12/26/08
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Re: A corrected design for USP4881801?
[Re: ed_turco]
#5645168 - 01/26/13 09:37 PM
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Quote:
I am even more amazed that the patent office let this squeak through.
I tried for an optical design patent and the examiner nailed me on too many points and I was justifiably turned down.
Look at this mount that recently got a patent:
https://docs.google.com/a/google.com/viewer?url=www.google.com/patents/US7752...
Seems to me they will give a patent to anything...
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