Eyepieces - Nurds only

[andrew s]

I have been trying to get better acquainted with eyepieces, the eye etc having been putting together a visual system. Several recent discussions have included eyepiece schematics and aberration diagrams. To better understand these I have Googled about and found two papers that may be of some interest,

The first one covers the modelling the combination of telescope, eyepiece and eye! I found it explained several points that had perplexed me especially about the eyepiece aberrations and spot diagrams, how they are done and what they mean.  http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECE_s.pdf

The second is the parent article to the first and covers the evolution of the eyepiece. https://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECES.pdf

Regards Andrew

[RT65CB-SWL]

Thank you for sharing @andrew s 

[rwilkey]

Hi Andrew, yes, these are exceptional papers and helped me a great deal in my early days.  Recently Chris wrote to me and we have been corresponding on a regular basis since.  Take care & clear skies!

[John]

Chris Lord is a member here but has not visited for quite a few years.

 

[rwilkey]

22 minutes ago, John said:

Chris Lord is a member here but has not visited for quite a few years.

Hi John, Chris lives in a place called Little Eversdon in South Cambridgesire now, we tried to meet up at the last IAS but ended up going different days after a misunderstanding!.

[DirkSteele]

My inner geek ( i prefer to think of myself that way) has been stirred.  Have started the first paper and already enjoying it immensely.  Thanks!

[Don Pensack]

Bear in mind some of the information is not accurate.  Plössl designed and was using his eyepiece in the 1830's for example, though

many on-line sources list it as 1860.  It's possible that is a date of patent and that it was designed much earlier.  Often the patent precedes the prototypes, but not always.

König was extremely prolific in his design years and it credited with 38 different designs.  So assigning the name "König" to just one eyepiece design is a bit, uh, selective.

Nonetheless, a lot of good info there.

[Paz]

These kinds of reads are right up my street, that thanks for posting.

[andrew s]

33 minutes ago, Don Pensack said:

Bear in mind some of the information is not accurate.  Plössl designed and was using his eyepiece in the 1830's for example, though

many on-line sources list it as 1860.  It's possible that is a date of patent and that it was designed much earlier.  Often the patent precedes the prototypes, but not always.

König was extremely prolific in his design years and it credited with 38 different designs.  So assigning the name "König" to just one eyepiece design is a bit, uh, selective.

Nonetheless, a lot of good info there.

Can you provide a more accurate reference at least to the key points of science if you feel there are errors in this area.

Personally I am less concerned with the history. 

Regards Andrew 

[bomberbaz]

Sorry that takes me into overgeek.

If I need technical help in future I shall ask one of you instead  😉

[andrew s]

8 minutes ago, bomberbaz said:

Sorry that takes me into overgeek.

If I need technical help in future I shall ask one of you instead  😉

You were warned on entry.  No refunds given.

Regards Andrew 

[Don Pensack]

19 hours ago, andrew s said:

Can you provide a more accurate reference at least to the key points of science if you feel there are errors in this area.

Personally I am less concerned with the history. 

Regards Andrew 

Well, the article deals mostly with history.  So far as I know, there are no inaccurate representations of design, but I didn't really dig that far into it.

Here is a thread you might find interesting:

https://www.cloudynights.com/topic/657067-comparative-raytracing-from-huygenian-to-ethos-and-beyond/?hl=%2Bray+%2Btrace#entry9278959

[vlaiv]

Pay no attention - just a nerd checking in ....

[andrew s]

55 minutes ago, Don Pensack said:

Well, the article deals mostly with history.  So far as I know, there are no inaccurate representations of design, but I didn't really dig that far into it.

Here is a thread you might find interesting:

https://www.cloudynights.com/topic/657067-comparative-raytracing-from-huygenian-to-ethos-and-beyond/?hl=%2Bray+%2Btrace#entry9278959

Thanks, I often use the telescopeOptics.net site which is liked in the CN discussion. It's very good I find.

What I especially liked about the first paper I posted was the modeling of the complete system, telescope  eyepiece and eye I had not seen that before. It also explained that the eyepiece aberations were derived by reversing the light as that had not been clear to me, although I had suspected it.

Incidently do you know anything about the Siebert Optics Monocentric IDs?

Regards Andrew 

[andrew s]

8 minutes ago, vlaiv said:

Pay no attention - just a nerd checking in ....

Your welcome.  Regards Andrew 

[Don Pensack]

34 minutes ago, andrew s said:

Thanks, I often use the telescopeOptics.net site which is liked in the CN discussion. It's very good I find.

What I especially liked about the first paper I posted was the modeling of the complete system, telescope  eyepiece and eye I had not seen that before. It also explained that the eyepiece aberrations were derived by reversing the light as that had not been clear to me, although I had suspected it.

Incidently do you know anything about the Siebert Optics Monocentric IDs?

Regards Andrew 

Yes, they are not truly monocentric.  In a monocentric, all the curves on the 3 elements have a common focal point.

The Sieberts, like the TMBs, are a 3 element eyepiece more closely resembling a Hastings triplet or a Steinheil triplet.

Siebert also makes them in fairly long focal lengths, to be used with his various Barlows to yield short focal lengths.

That's not a bad idea since it greatly expands the eye reliefs (very tight on monocentrics), and reduces induced astigmatism in the eyepiece, making them usable at shorter f/ratios.

Harry doesn't give eye relief or field stop data on them, though some users have mentioned about a 30° field.

[andrew s]

Thanks @Don Pensack I might give some a try. I have a Takahashi Mewlon 180 and at f = 2160mm I don't  need that short a focal length eyepiece.  Indeed many modern planetary eyepieces seem targeted at smaller aperture and focal length apos.

Regards Andrew 

Edited July 14, 2020 by andrew s

[JeremyS]

1 hour ago, vlaiv said:

just a nerd checking in ....

Did someone call?

🙂