24 replies to this topic

[Crayfordjon]

This thread is a spin off from the Hypo thread as the discussions have wandered from the main philosophy of the Hypo design. I evolved this configuration from my long term research into dialytes and it resultd in a thirty inch refractor that I built for the Hanwell public obervatory. Peter Wise took this design and brought out his own version and produced the Zerochromat which is apochromatic with a Strehl of 0.998. I have built several more of these scopes since and it was during analysis of the optics on one of them on the optical bech that I discovered the Hypo effect.

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[Mark Harry]

John, you asked a question- where is.....etc.
At my post, look at the "attachment". Click on that, and the whole OSLO file comes up, as Robboski asked for. You have to click on the central square that yaks about OSLO, and it'll close, and come up with a data board, draw board, and lens board.
If you have downloaded OSLO (which I think you said you have) you can click on any of the icons in the upper right on the draw board; and plots, MTF, 2D, 3D etc can be viewed.
This whole file can be manipulated if you choose.
I'll post it here, too. If you can't find it, I could save a basic layout in 2D, and put data and plots of it if you want. (For a 4" F/9.6~)

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•  5029966-mike's 4inch dialyte F9.634 better.len   544bytes   114 downloads

[Mark Harry]

Here's the 2D

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[Mark Harry]

Intercept graphs

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[Mark Harry]

Spots

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[Crayfordjon]

Thanks Mark. It looks superficially that you have a Petzval dialyte type configuration, it does make for a shorter scope than retro.

[Stipe Vladova]

This looks promissing! It means that the lateral color on f15 will be much less visible than on f9,634! Barely wait to get 150mm f17 O.G.!

[Aljr]

The Design for Retrofocally with OG lens 150/2600mm. This design is present in Hanweel Telescope(30"). No mistake here.
The "crazy eyepiece" is not authentic. It was created using experiments in "real performance".

[Aljr]

Please, attention to Flint Corrector.

[Mark Harry]

But it's essentially a dead ringer for your basic HYPO, and the predicted performance isn't too shabby!
If the objective is going to be ground anyways, it might be beneficial to bend it as shown.....
Mark

[Crayfordjon]

You should reconsider the Hypo as a second string option just to try it out. This image has only been enhanced slightly, but the lack of colour is evident, this is my latest design for the imaging Hypo.

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[Stipe Vladova]

Much better image quality than of the Hypos in old thread.

Is this yellowish image due to fringe killer?

[Crayfordjon]

I have improved the performance to a point where images are quite acceptable, I am now interested in the Hypo as an imager and there seems to be real potential there. The slight yellowish tinge is low sunlight and a bit of enhancedment on Photoshop, although that was not nescessary. No filters are used.

[gatorengineer]

John,

I am a novice to understanding optics, but I dont understand why your four lens corrector assembly couldnt not be a stand alone corrector for any achcromat? E.G. if you started with a 6" F8 Synta scope as an example, what would the spots look like before and after? or perhaps this is just a variant on the Petzval solution, and a cousin to the Chromacorr?

[Mark Harry]

I changed the aperture of the dialyte for F/15, and the error on axis was 1/4 wave for RGB (!) Not bad, I would think.
********
This thing isn't a Petzval, John. It looks just like your Hypo. There are no separated stand-alone flint elements.
M.

[Crayfordjon]

Gotoengineer, no the corrector is integrated with a singlet plano convex crown objective lens, it will not work for another achro doublet.

[Crayfordjon]

Mark I stand corrected, you are right, a Petzval has a stand alone flint corrector integrated with a doublet which is very over corrected giving Hyperchromatic over correction by itself, this is balanced by the chromatic OG to produce white images ( nearly). Your solution is a Hypo type. Gato engineer, the Retro is not a Petzval as the corrector is in the retrofocal position. The Petzval is a classical dialyte. The Chromacor is another species of colour corrector which I believe is placed near the eyepiece, I have never seen one or seen an optical diagram of one and I think it is designed to correct for residual colour in the image, somebody clear his up for me?

[Crayfordjon]

Tipe I send a raw image of the test object.

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[Stipe Vladova]

150mm f17 came from Surplusshed!



But unfortunately it is very bad polished! It has very bad zones and is so thin for me to repolish it. It is unable to focus to form any usable image! The zones are so strong that the lens has double curved front convex surface! It serves as test lens for examining the corrector lenses to see colorcorrection. At least one benefit.



It is not BK7, it is plate glass. Dialyte configuration really works with surprisingly little color with this lens. So I went to the local glass workshop and purchased 162mm dia by 10mm thick plate glass to grind a new lens. I saw the plate glass refracting index properties are similar to BK7 crown.

[Crayfordjon]

If it is Chance Pilkington float glass then you will find that the homogenuity and transmission without serious striation are excellent if fact you will probably find no striations at all for 160mm. The refractive index is the same as BK7 as far as what you are going to use it for, I have been using this glass for some time now and I have had no trouble.

[Stipe Vladova]

No Pilkington in Croatia. We here are far away to have such glass in any workshop. This I bought is greenish float glass for mass producing.

This is the link to see ATM status here in Croatia. Very sad. I was born in totally wrong corner of the world for ATM.

[Crayfordjon]

If it is float glass it probably would be all right, I think the stuff is available all over the planet. Try putting the piece of glass in front of the OG of your largest telescope and view the disc of white light after removing the eyepiece and training the scope on a street lamp at night. You will see the striations if they are there. A piece of pre float, old green plate will look like a paling fence.

[Crayfordjon]

Wow! Stipe I really feel for you, what bad luck, it is a pity that there is so much resistance to imports of the right materials for telescope making. You can be ingenious and learn to recycle anything that can be useful to build a scope, when I started back in the 1950's in the UK, there was nothing here either, however I bought my first carbo from The Carborundun company who sold small lots for the individual. I got my first glass 6 inch blanks from Chance, and bought the jewellers rouge from the local chemist ( you cannot do that these days, they look at you as you were daft). But the scope was a different matter, there was nothing available even wood was rationed as we were still in a war situation, so I took to scavenging in rubbish tips for bits and pieces, we learned to recycle in those days nothing is new. ATM is mostly dead in the UK, there are a number of dedicated ATM's still but the trend is to buy everything new, and pay the price, and some of the scopes sold for a high price are rubbish!.

[Stipe Vladova]

I strongly agree with you John! Most modern day amateurs rather like to buy than make! Here in Croatia at our website for croatian astronomers you can meet astrophotographers who appreciate only buying some expensive APO and Canon EOS 5D MKII. That's pretty expensive equipment! Not so much people can afford such a thing. They do not know anything about that equipment making or its optical properties. I know much about optics that I learned in the past 12 years, but probably will never buy Canon or some expensive APO with flattener and various contrast boosting and other expensive stuff. When I try to talk to them about optics, aberrations or such, they're not interested because only like to buy and use.

[Crayfordjon]

Its fashionable to own a triplet apo, the recieved opinion is that if it is not an apo its useless. I am getting imaging results from my Hypo that could rival a triplet, if not come pretty close, the pic of the the tree indicates that. A hypo can cost a hundreth the price of a fashionable apo.