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Eyepiece anatomy video

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#1 4thpage

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Posted 16 May 2018 - 01:36 PM

I'm wondering if anyone has come across any good videos detailing the guts of an eyepiece...especially with it disassembled and such. Purely for knowledge sake.

#2 havasman

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Posted 16 May 2018 - 02:20 PM

Not video but see section 12.3 for some info regarding lens configurations and orientations.

 

http://www.telescope...BLE_OF_CONTENTS

 

There are some x-rays of Ethos and ES100's out there too.


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#3 4thpage

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Posted 16 May 2018 - 02:26 PM

Not video but see section 12.3 for some info regarding lens configurations and orientations.

 

http://www.telescope...BLE_OF_CONTENTS

 

There are some x-rays of Ethos and ES100's out there too.

Thanks! Now that I've moved up to some higher quality eyepieces, I've become more Curious what's really going on inside.



#4 aeajr

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Posted 16 May 2018 - 02:44 PM

Eyepiece Designs -  This is the one I turn to when I am trying to understand
or explain the differences between the various designs.  There are so many
different designs.  Many are named for their original designer, such as
Huygens, Ramsden, Kellner, Plossl, Konig, Erfle, Branden and Nagler.
http://www.chuckhawk...ece_designs.htm


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#5 4thpage

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Posted 16 May 2018 - 03:09 PM

Eyepiece Designs -  This is the one I turn to when I am trying to understand
or explain the differences between the various designs.  There are so many
different designs.  Many are named for their original designer, such as
Huygens, Ramsden, Kellner, Plossl, Konig, Erfle, Branden and Nagler.
http://www.chuckhawk...ece_designs.htm

Thanks! Yes, this is a good one I've read up on before, and go back to frequently.


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#6 Starman1

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Posted 16 May 2018 - 04:07 PM

It's far far worse.

This link doesn't even contain many of the newest offerings:

http://www.quadibloc...ience/opt04.htm  (go down the page a bit).

or this:

https://www.cloudyni...eces/?p=8449237

It shows the Pentax XW with 7 lenses, when the range is 6 to 8 elements depending on focal length.

or this:

http://www.brayebroo...NS/treediag.jpg

 

Nowhere are there cross-sections of the innumerable new designs like: https://www.google.c...MhpgR_XQmRQ_mM:

or

https://www.google.c...6qr0tMvYzlwamM:


Edited by Starman1, 16 May 2018 - 04:11 PM.

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#7 4thpage

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Posted 16 May 2018 - 08:17 PM

Thanks, you guys. I'm trying to figure out why the top lenses on two of my EPs (GSO 30mm/68° and Baader Morpheus 6.5mm/76°) are so much larger diameter than the one on my 18mm and 24mm 82° Explore Scientifics.


Edited by 4thpage, 16 May 2018 - 08:18 PM.


#8 4thpage

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Posted 16 May 2018 - 09:17 PM

This link doesn't even contain many of the newest offerings:

http://www.quadibloc...ience/opt04.htm  (go down the page a bit).

or this:

https://www.cloudyni...eces/?p=8449237

It shows the Pentax XW with 7 lenses, when the range is 6 to 8 elements depending on focal length.

or this:

http://www.brayebroo...NS/treediag.jpg

Thanks! So it just depends on the design of the EP, how big the top lens is? Here are mine in question: ES82 18 and 24, Morpheus 6.5, GSO 30

 

20180516_220612_resized.jpg



#9 Starman1

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Posted 17 May 2018 - 12:30 AM

The size of the top lens is determinative of the eye relief.

Draw a triangle with the exit pupil as the apex and the width of the lens as the base.  

The angle at the apex is the apparent field of the eyepiece.

Some eyepieces have oversized eye lenses, but not many.

So, to wit, take two eyepieces of identical apparent field, yet one has an eye lens 1/2 as wide.

That eyepiece has 1/2 the eye relief of the other.

If you want long eye relief and wide field, the top lens will be large.



#10 4thpage

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Posted 17 May 2018 - 07:39 AM

The size of the top lens is determinative of the eye relief.
Draw a triangle with the exit pupil as the apex and the width of the lens as the base.
The angle at the apex is the apparent field of the eyepiece.
Some eyepieces have oversized eye lenses, but not many.
So, to wit, take two eyepieces of identical apparent field, yet one has an eye lens 1/2 as wide.
That eyepiece has 1/2 the eye relief of the other.
If you want long eye relief and wide field, the top lens will be large.


Brilliant! Thank you! I am learning a bunch of from those links you sent as well.

#11 radium226

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Posted 17 May 2018 - 12:40 PM

For me, it helps to think of the system like this: you can use a magnifying glass to look at small text on a sheet of paper.  The objective of a telescope creates a real image of the sky at the focal plane of the telescope--then you're just using the eyepiece to look at that image, just like holding a magnifying glass up to a sheet of paper.  The two variables are then: what's the quality of the image your telescope is producing; and what are the qualities of your "magnifying glass" (the eyepiece).

 

Another helpful abstraction for me is to understand that a lot of modern multi-element lenses are really simpler designs with a built-in barlow.  I believe the Naglers are essentially this.  If you're asking the question I think you're asking (a very broad "why are these so complicated and what do all those elements do?") then I hope these two tips are helpful.  I personally found the "designs" section of the wikipedia article helpful, too: https://en.wikipedia...yepiece_designs


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#12 4thpage

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Posted 17 May 2018 - 01:04 PM

For me, it helps to think of the system like this: you can use a magnifying glass to look at small text on a sheet of paper. The objective of a telescope creates a real image of the sky at the focal plane of the telescope--then you're just using the eyepiece to look at that image, just like holding a magnifying glass up to a sheet of paper. The two variables are then: what's the quality of the image your telescope is producing; and what are the qualities of your "magnifying glass" (the eyepiece).

Another helpful abstraction for me is to understand that a lot of modern multi-element lenses are really simpler designs with a built-in barlow. I believe the Naglers are essentially this. If you're asking the question I think you're asking (a very broad "why are these so complicated and what do all those elements do?") then I hope these two tips are helpful. I personally found the "designs" section of the wikipedia article helpful, too: https://en.wikipedia...yepiece_designs


That does help, thanks!

#13 SandyHouTex

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Posted 20 May 2018 - 01:55 PM

Something you should know, is that all of the “Monocentrics” out there, aren’t.  Even the old Zeisses that people pay $1000 for.  Internally they’re just Hasting triplets, which are typically used in jeweler’s loupes.

 

Another lie is “Plossl”.  No one makes them anymore.  A Plossl, as designed, uses three types of glass and comprises 4 elements in 2 ASSYMETRIC groups.  The Plossls currently being sold by all manufacturers are really Symmetricals, which use 2 glasses in 4 elements and 2 SYMMETRICAL groups.

 

It goes on and on.


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