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The Definitive Newtonian Reflector

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#51 pastorgalactico

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Posted 22 January 2017 - 08:03 AM

Hello;

I have used one of those websites and it gives me these results.
But do not interpret those graphs.
I have calculated them for eyepieces of 31.7mm and 50.8mm.
Most are 31'7mm eyepieces.
I have the complete series of eyepieces of scientific depth of 82º.

The ideal one is the blue graphic?

capturada.jpgcapturada_A.jpg


Edited by pastorgalactico, 22 January 2017 - 09:35 AM.


#52 wcw

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Posted 22 January 2017 - 11:56 AM

pastorgalactico,

Since this thread is about Ed Turco's Definitive Newtonian Reflector, we should stay on that topic, ok?

If you would like to know more about Mel Bartels' Diagonal Off Axis Illuminator, perhaps you may want to start your own topic or PM me and I can try and help you.

 

It appears you entered the diameter of your eyepieces in the place where you are supposed to enter the field stop diameter of the eyepieces.

 

-Bill



#53 ed_turco

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Posted 25 January 2017 - 02:10 PM

pastorgalactico, as you say, selecting the size secondary is a matter of balancing trade-offs.

These web sites are useful for calculating size of secondary:

https://stellafane.o...b/newt-web.html

and

http://www.bbastrode...om/diagonal.htm

To use this one, do not enter anything for secondary size. Fill in all the other blanks and then click "Update chart".

 

Hope this helps.

-Bill

You have to remember that the diagonal sizes predicted by those programs don't take into effect the use of a Barlow lens.  I had a 2x Barlow and a .75" diagonal.  Since then, it has been easier to use a 1" diagonal as alignment with the smaller diagonal can get rather tedious.  I see no difference between the two sizes when observing, but I'll bet those APO owners would see differences that either aren't there, or below the sensitivities of their eyes.

 

Do you know that the experts place the beginning of visibility of central obstruction effects anywhere from 10% to 30%?

 

 

ed



#54 pastorgalactico

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Posted 26 January 2017 - 10:02 AM

Hello;

I have already decided to put a secondary 82mm of minor axis thinking that I will then put a comma corrector of scientific data and need an extra focus stroke of 32mm.
Attached is a drawing so you can see the project in detail.
If there were any errors in the project I would appreciate it if they commented before making a mistake.

Regards;

J.Tapioles

 

Plano_focal.jpg



#55 ed_turco

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Posted 19 February 2017 - 11:53 AM

I am so pleased to see this discussion continuing so long after my article.  Hopefully some new Definitive Newtonians will be built as a result.  I stop by on CN from time to time and if anyone feels that they have a question or wishes me to get back in the discussion, please contact me by personal email.  Then I can check by far more regularly to help out.

 

Any takers?

 

 

ed


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#56 Zachrey

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Posted 28 May 2017 - 01:55 AM

When I worked at Advanced Optics in 1983, I helped make an optical window for my boss. It was a a lot of fun! I don't think I saw the final result, but I remember him telling me to make it a wedge instead of two parallel faces so you don't get an interference pattern when you look through it. It was a square piece of glass about 1/4" to 1/2" thick and about six inches on a side.

 

We looked at it with a collimated light source (He had a fairly large sperical or paraboloidal mirror on the floor and a cardboard tube over it and a light shining on it so the rays coming up were parallel). After the initial polish, we saw that there were a lot of closely spaced fringe lines because I ground it so it was a slight wedge, which is what he wanted.

 

So if I made a window for a Newt. would it have to be a wedge or should the faces be parallel?



#57 ed_turco

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Posted 19 April 2018 - 12:05 PM

I finally saw this.  Don't believe any of that bull do-do about wedges or wedgies or whatever.  All my windows are plane parallel and I've never seen a ghost image.



#58 Mark F

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Posted 21 May 2018 - 08:41 PM

Great article, and well-thought out.




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