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Hypo/Dialyte testing discovery

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#51 Crayfordjon

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Posted 07 December 2012 - 03:34 AM

Sticking to Schupmanns is OK but this special case dialyte is a Catadioptric refractor and has severe limitations inherent in the optical design. Petzval type and retrofocal type dialytes are open to almost infinate adaptation and evolution, that is why the technology is so fascinating. If it is considered an exersize in futility then those who do so are lacking imagination and the inventive spirit that pushes human knowlege forward. In Science we have two kinds of scientists, those who say " it cant be done" and the other kind who see that an idea might have great potential even if it proves to be a dead end in the long run. I am the second kind.

#52 Mark Harry

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Posted 07 December 2012 - 08:51 AM

Yes, pardon the error!
M.

#53 kfrederick

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Posted 07 December 2012 - 09:05 AM

John you are my kind of ATM not afraid to try something unproven .Some new way of doing things .So glad you share on here .

#54 Gary Fuchs

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Posted 07 December 2012 - 10:06 AM

Yes, pardon the error!
M.


Maybe just a Freudian slip? So then I don't have to retract my question about tools and techniques for making that lens...

Gary

#55 MKV

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Posted 07 December 2012 - 10:29 AM

Crayfordjohn, I believe I said "if I decided to make a dialyte..." not "if I decided to experiment with a dead-end design". If you have two known solutions and one gives perfect images while the other doesn't, then choosing the latter is an exercise in futility, imo.

If you have new techologies then further investigation is in order, but reinventing the wheel is and always will be an exercise in futility.

For those who are not familiar with the Manigin dialyte systems, here is one Mike I. Jones designed and posted on CN some time ago of a 5.5 inch f/7.4 system. The spectral range, in case you wondered, is from 400 to 900 nm! The field is 1.4 degrees (1 inch) in diameter. Try that with Rohr's configurations.

Mladen

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#56 DAVIDG

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Posted 07 December 2012 - 10:49 AM

DAVIDG, personally if I decided to make a dialyte I'g do with a Mangin mirror rather than an achromatic lens corrector. Using three single elements, all of the same (cheap) BK-7 variety, you can achieve full apochromatic color correction, no lateral color to speak of, flat field, fully anastigmatic performance at just about any focal ratio (from f.3.5 and slower), large field size, closed tube, no aspherics, and the whole telescope mounted on a low gravity, stable mount.

Rohr's refractor-type solutions just seem like needlessly expensive exercises in futility. In fact, he removed his home page because the designs are outdated!

Mladen


Mladen,
Exactly! That is why I build Schupmanns. By the way, those are not "Rohr configurations" but a discussion by Roger Ceragioli about different refractor designs and the link I provided was a paper that Roger had posted. The material was expanded upon and became part of his new book and excellent book on optics "Telescope, Eyepieces and Astrographs".

All the Best and Happy Holidays,
- Dave

#57 kfrederick

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Posted 07 December 2012 - 10:56 AM

Yours has a large obstruction and is a reflective system . All is not yet known . I know only good thing come from smart people trying new things .When they fail sometimes that is when most is learned .Nothing like having the real telescope to learn from . Obstruction effects are real but we are use to seeing it in the images . Having a design in OSLO is not like having the real telescope . Mark and John knows what he is doing we should relax we might all learn some.

#58 Mike I. Jones

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Posted 07 December 2012 - 10:59 AM

Thanks for resurrecting that one, Mladen. I need to ping Dane and see if he ever built it. Shoulda been/will be a sweet scope.
Mike

#59 MKV

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Posted 07 December 2012 - 11:01 AM

Thanks DAVIDG. Happy Holidays to you too.

Mladen

#60 Dave O

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Posted 07 December 2012 - 11:16 AM

Mladen -- looks to be a variation of the Busack/Honders -- a very elegant design to be sure ... however ... it IS obstructed. For many, a central obstruction is noticeable, particularly as a loss of contrast, which is one reason refractors are still very popular in spite of their high cost; as well as many ATMs venturing (with great success I might add) into the tilted mirror telescope designs.

I think this particular design has potential; but unless folks are willing to experiment (play?) with them, that potential may never be realized. The Busack/Honders came about around 2000 or so ... only three elements, all spherical surfaces, common glass and you get as perfect an image as you could ever hope for (in an obstructed system) ... what took so long? There are still things that have not been 'discovered' and only by looking will we ever find them.

#61 MKV

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Posted 07 December 2012 - 11:27 AM

Yours has a large obstruction and is a reflective system . All is not yet known . I know only good thing come from smart people trying new things .When they fail sometimes that is when most is learned .Nothing like having the real telescope to learn from . Obstruction effects are real but we are use to seeing it in the images . Having a design in OSLO is not like having the real telescope . Mark and John knows what he is doing we should relax we might all learn some.

You're right kfredrick, the CO is 1/3 the CA but that's because Mike I. Jones designed it for Dane as an astrograph with a huge field at that focal ratio. If you wanted smaller field you'd have much smaller central obstruction without serious diffraction effects.

I used Mike's configuration as an example of Mangin dialytes are capable of (mind you, at f/7.4 not f/15!), compared to dialyte refractors. The Mangin dialiyte is a true apochromat over a hughe spectral range, and a true flat-field anstigmat (no spherical aberration, coma or astigmatism to speak of) - and this is all possible with the cheapest glass (BK7, for all three elements. No exotic, expensive glasses needed!

As they say, it's hard to argue with success. :)

Obviously if I had to choose a dialyte I would go for a Mangin catadioptric system. If I wanted to experiement with different configurations, then all options are open. However, pursuing the ones already tried and retired seems to me somewhat pointless. That's all.

Reagrds,
Mladen

#62 Crayfordjon

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Posted 07 December 2012 - 11:30 AM

In spite of all that, the retro has no central obstruction or a tilted mirror, it has been perfected by Peter Wise and is an APO, it is cheaper than most with a very high performance, I stick to my guns on this and will always look for news ways to do things, no matter if certain dsigns are the "last word", they are not.

#63 MKV

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Posted 07 December 2012 - 11:38 AM

Thanks for resurrecting that one, Mladen. I need to ping Dane and see if he ever built it. Shoulda been/will be a sweet scope.
Mike

Hi Mike, yes that was a definite keeper. Thanks. I am also curious if Dane gave it a try. If I remember the discussion of these, the clincher is the Mangin mirror which is in effect a Maksutov-like meniscus with all the thickness, and radius of curvature spot-on requirements that come with it. Also, the back surface of the Mangin has to be a super smooth, zone-free surface of reflector quality. Being convex, it would require advanced techniques and tooling to achieve.

So, I can understand why then a dialiyte refractor may be more attractive for novices, but there is no question which is a better optical system.

regards,
Mladen

#64 MKV

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Posted 07 December 2012 - 11:55 AM

Hello Dave O. The central osbtruction in this case is large (but not too large) because the system is an f/7.4 and designed to cover a large field. If you were to make it an f/10 then the CO will be smaller as well. As long as you can keep the CO about 20-25% of the CA the diffraciton effects are not too injurious.

I understand the fascination with unobstructed telescope, but, what's the point of having a slower, longer, more cumbersome system with no central obstruction and obvious uncorrected chromatic halo around bright images?

If I had to choose an unobstructed system and perfect color correction I would go with a Schiefspiegler, not a dialiyte refractor. Why bother with lenses?

However, let me be clear about something. It looks like some have misread intentions in what I wrote that are not there, so I want to stop it before it continues in that direction: There is nothing whatsoever that I wrote to DAVIDG that should be construed as criticism of experiments, or resistance to research in general. I simply stated that "if I had to choose a dialyte..." then I wouldn't waste my time with known/existing designs of inferior quality. Nothing else should be read into that statement. Thank you.

regards,
Mladen

#65 MKV

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Posted 07 December 2012 - 11:57 AM

In spite of all that, the retro has no central obstruction or a tilted mirror, it has been perfected by Peter Wise and is an APO, it is cheaper than most with a very high performance

Do you have his design to share?

Mladen

#66 Ed Jones

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Posted 07 December 2012 - 07:03 PM

Mladen,
The Jones-Medial is a refractor that has no obstruction, color, coma, field tilt and uses 3 pieces of common glass. I am at the assembly/testing stage on mine although I haven't had much time to work on it the last few months.

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#67 kfrederick

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Posted 07 December 2012 - 07:30 PM

Nice design ED If I was building it I would try my interlocking box with slots for the plates to hold the optics like I used on the CHief

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#68 jgraham

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Posted 07 December 2012 - 08:32 PM

Very, very cool Ed. I'm looking forward to your reports on this one.

#69 Dave O

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Posted 07 December 2012 - 10:44 PM

Wow Ed! You lost the obstruction and it didn't even cost more glass! Looks to be a dandy! :)

#70 MKV

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Posted 08 December 2012 - 12:02 AM

Mladen,
The Jones-Medial is a refractor that has no obstruction, color, coma, field tilt and uses 3 pieces of common glass. I am at the assembly/testing stage on mine although I haven't had much time to work on it the last few months.

That's the way to go Ed! Beautiful images. The Manign dilaytes are a proven design for fully corrected apochromatic configurations, in Newtonian, off-axis and Cassegrain modes. And no exotic glasses needed! Very impressive.

I would be curious if you could share with us the problems and challenges producing the Mangin mirror.

BTW, here is another Mike I. Jones original - a Cassegrain dialyte solution he and I talked about a while back: all spherical surfaces, fully apochroamtic and anastigmatic performance, simple N-BK7 glass.

Imagine, instead of a cumbersome Schmidt corrector plate, the front corrector is just a simple plano-convex lens! Think how much cheaper would it be to make catadioptric Cassegrainss this way. It brings such configurations into the ATM realm. This one doesn't even require a field lens! (the secondary is also a Mangin mirror)

This 8-inch f/20 design would make a fantastic, compact planetary scope to die for and perfectly executable by advanced amateurs!

Mladen

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#71 Crayfordjon

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Posted 08 December 2012 - 02:00 AM

Another Schupmann yet. :foreheadslap: :help: :tonofbricks:

#72 Crayfordjon

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Posted 08 December 2012 - 03:16 AM

Mark, does the Ed Jones Medial really belong on this thread? It is not a really a new idea in optical thinking, it is definately not an "outside the box" conception, which your design is! we have regressed into a mere recycling of the same old tired designs.

#73 nytecam

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Posted 08 December 2012 - 03:59 AM

Another Schupmann yet. :foreheadslap: :help: :tonofbricks:

Hi John - Mark Harry's thread been highjacked - why do I get the strong impression some experts don't like your design - again :p
Of course anyone can reintroduce the original thread right here -right? [I love the 'right?' americanism] :jump:

#74 Mark Harry

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Posted 08 December 2012 - 07:32 AM

I'm just sitting back eating popcorn, or sipping a cup of Joe. (and tinkering away...)
M.

#75 Mike I. Jones

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Posted 08 December 2012 - 08:35 AM

Post deleted by Mike I. Jones






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