Have you ever heard of the Schupman telescope?
Posted 27 November 2013 - 07:24 AM
Posted 27 November 2013 - 07:41 AM
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Posted 27 November 2013 - 11:06 AM
Posted 27 November 2013 - 12:33 PM
For an ATM one has to consider how difficult the design is make vs the cost and performance. The fact that multiple examples of Schupmanns have been made by amateurs is a big plus for the design along with the fact that a book has written on how to make them. It is has 5 surfaces and depending on the design either all 5 are spherical or 4 out of 5 are. It is made from two pieces of cheapest optical glass you can buy that is BK-7 and the tolerance are much looser then a typical achromat let alone some more exotic design that don't perform as well and have more elements.
I made three optical set on my kitchen table. As for testing it was done using a typical knife edge test and Ronchi screen. The only device I had that the average ATM doesn't is an optical flat to do double pass autocollimation but if your going to do lens work an flat is piece of equipment you need. Flats show up on places like Ebay and for not much money.
Here is a picture of 4" f/12 I made. The cost of the optics and OTA was under $100. What 4" APO can you buy for under $100 ?
Posted 27 November 2013 - 02:00 PM
Posted 27 November 2013 - 02:05 PM
Posted 27 November 2013 - 02:38 PM
Here is the optical layout and spot diagram for my 4" f/12. It is the typical optical layout made by Atm's. The small field lens in the above drawing has been replaced by a small spherical field mirror. It is easy to make and reduces the size of the OTA by folding the light path back on itself. What is not shown is a built in star diagonal to place the focuser on top of the OTA as you see in pictures I've posted of the Schupmanns I've made.
You can also see from the spot diagram that the in focus row of spots which is the middle row show all the wavelengths well within the Airy disk. Hence zero false color.
Posted 27 November 2013 - 02:51 PM
That is one of great features of a modern Schupmann. The average guy can build them. Here is a picture from Stellafane a few years ago were 5 of them showed up. They range in diameter from 4" to 7".
Posted 27 November 2013 - 09:08 PM
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Posted 30 November 2013 - 06:22 AM
You can't have everything in a design - all is a compromise.
Posted 30 November 2013 - 08:14 AM
Posted 30 November 2013 - 01:07 PM
Here is a picture of another homemade Schupmann by Gerry Logan from 2012. It is a 7" f/10 in which Gerry added an optical flat to fold the light path so the OTA is only about 3 feet in length.
Posted 01 December 2013 - 02:00 AM
Posted 01 December 2013 - 02:39 AM
If you ever collimated a newt and found it hairy, don´t bother with a Schuppman. It has 1 extra set of alignmentscrews at the relay-mirror.
Those are the screws you use to tune out atmospheric dispersion as well.
It just plain works if you make a good solid tail-piece assembly which holds the focuser, diagonal and the relay-mirror and allows you to tweak them all.
Furthermore a Schuppman is relatively light.
A 30cm schuppmann has about the same mount-requirements as a 7 inch Apo.
Posted 01 December 2013 - 05:47 AM
The dialyte refractor that I designed from John Wall's 30 inch dialyte worked very well indeed, but was far too expensive to make, and I had trouble with the triplet lens in the corrector chain of lenses. Not commercially feasible.
The latest configuration makes use of an absolute minimum of corrector lenses (one singlet and two identical doublets), and even has half the lateral colour of the original design, with identical performance on-axis. It has the bonus of not being 'tweaky' at all.
Posted 01 December 2013 - 08:59 AM
John I know what you are saying Same thing with the Chief It is better and could be even better!! But even the people who know will say not say . The big boys have no intrest in a better telescope and the ATMs just wont to by a cheep mirror and put it in a tube and call them ATM / Nothing wrong with a Schup why none out there except for ATM ? The pros do not seem interested in a better telescope design .Taking a chance . I respect the work you and Peter have done . And excited to see what you come up with next .
Yes we have heard of the metre swedish scope usual, but what we are trying to do is introduce new ideas into ATM, and our experience is that new ideas are rejected on a knee jerk regularity, Why?, I find this fascinating this resistance to change.
Posted 01 December 2013 - 11:36 AM
I keep seeing talk about some of these new design but I have yet to see a step by step plan on how to build one. For other designs there are books, articles and website that provide the EXACT details on how it is done. This is true of the Schupmann and why it has been built. Showing a one or two examples doesn't cut it. Show the world EXACTLY how to build one, the cost involved, were to get the materials, how to make and test the optics, what the tolerance are and then maybe you'll get a following.
Posted 01 December 2013 - 05:19 PM
. In a similar vein, the Schiefspeigler design has also not been commercialised - I made a 4 1/4 inch Schief back in 1976, and made much use of it, showing dozens of schoolchildren at my son's school the wonders of the night sky. Even a party of nuns! It was 'tea and stars' and was a resounding success - and provided free. All under the wonderful South African skies.
The Kutter Schief has been commericalized by a couple of companies over the years. It is still being sold by AOK Swiss in both a 4" and 6" aperture. http://www.aokswiss.ch/index_tel.html It is also still popular with ATM's and we have an active site on Yahoo Groups "Schiefbuilders". From the information on this site a number of Schiefs have been built over the years. Again the secret is to provide people with exact plans and information on how it is done and examples of scopes that have been built so they can see it is a doable project. Also when people do look thru the eyepiece they do show great images and show it is worth the effort to make one. Here is a picture of one made by my good friend Gary Fuchs.
Posted 01 December 2013 - 11:11 PM
Schiefs and Schupmanns are great scopes.
When I made my Schief an otherwise knowledgeable friend commented that they're hard to collimate. In fact, they're quite easy to collimate--provided you set up the adjustments the way Knab shows. I think it's considerably easier than a Newt. And they seem to hold it quite well too, even through fairly rough handling.
Dave recommended that I follow Knab's method--and I did. Like Dave said, that was well documented and even without a technical/scientific background I was able to understand and implement it. If I can do it...
As for why these scopes aren't more accepted commercially and known, I think it's partly because of the sort of mistaken preconceptions like those I encountered from my friend and others subsequently.
The information and guidance is easily available for either scope. Likewise the materials and tools needed--nothing fancy.
To me it's like choosing a car. Which one is best; which of course depends...a minivan isn't better than a sedan and that's not better than a roadster. Apples and oranges.
Posted 02 December 2013 - 01:57 AM
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