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Oversize or giant eyepieces custom made for large observatories

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#1 Nightfall S Africa

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Posted 11 August 2020 - 06:27 AM

Some years ago I read a post (on CN, I believe) that described and showed pictures of rather giant eyepieces that a specific manufacturer custom-made for large observatory telescope visual observing. The drawtube diameters were on the order of 3 or 4 inches as I recall. Can anyone help me find either that post or the name of the manufacturer?

 

While we are at it, which eyepieces does the 82-inch MacDonald Observatory in Texas employ during the public observing sessions?



#2 nicknacknock

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Posted 11 August 2020 - 06:33 AM

I think you are looking for eyepieces by Harry Siebert.


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#3 luxo II

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Posted 11 August 2020 - 07:13 AM

And a few by Masuyama.



#4 TOMDEY

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Posted 11 August 2020 - 08:54 AM

Well... the 82-incher... the minimum magnification (dark-adapted eye, open pupil) will be around 400x, 5.2mm exit pupil... for most people. That Cass focus is presented at F/13.7 - so the needed eyepiece would need to have a focal length of ~70mm. The Masuyama 80mm is therefore about right, operating at 357x, with a 5.8mm pupil. If one's reasonably-young eyes are dark-adapted, that should provide good views without central black-out. If the SM shadow erupts, will have to go to shorter focal length and higher power.

 

The aperture and F# entirely drives your eyepiece selection. Note that the Cass slow feed allows modest eyepiece design to work well...

 

I made this selection graph some time back >>> Note that BIG scope, cass focus (or long refractor) puts you in the upper right region for eyepiece selection.    Tom

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  • 84 95 EYEPIECE GRAPH 11 jpg Tom Dey.jpg

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#5 Nightfall S Africa

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Posted 12 August 2020 - 02:45 PM

Yup. Siebert it was. Didn't know about Masayuma, so thanks too for that! =Dana



#6 Thomas_M44

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Posted 12 August 2020 - 11:54 PM

I understand a Masuyama eyepiece is used with the 60-inch Hale telescope on Mount Wilson.  It's an 80mm, I believe.

 

A 100mm eyepiece is also used, but not sure if it too is a Masuyama or crafted by another maker.

 

Here's a relevant web piece that is very interesting:

 

http://www.scopeview...untWilson60.htm

 

I also heard that Gary Russell of Russell Optics has made large eyepiece/s for telescope/s at Kitt Peak National Observatory in Southern Arizona, but don't know any additional details.


Edited by Thomas_M44, 12 August 2020 - 11:58 PM.

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#7 nicknacknock

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Posted 12 August 2020 - 11:55 PM

Gary still advertises up to 85mm 2" Plossls :)



#8 Mitrovarr

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Posted 13 August 2020 - 01:02 AM

That picture makes me wonder why more eyepiece lines don't have a model at the 1.25" and 2" ceilings.

 

It seems like a natural place, but the only ones I can think of that do it are the Panoptic line and the ES 68 degree line (which isn't dead on but is close).



#9 Disciplus55

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Posted 13 August 2020 - 02:45 AM

Clavé made 45, 55, 65 and 75mm eyepieces in 2”.



#10 havasman

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Posted 13 August 2020 - 07:50 AM

I also heard that Gary Russell of Russell Optics has made large eyepiece/s for telescope/s at Kitt Peak National Observatory in Southern Arizona, but don't know any additional details.

Yes, Gary made me a copy of a 63mm Konig that uses his "XL" lenses and is a copy of one he made for Kitt Peak. It has a 2" barrel. It's very good at f10 in the club's 16" LX200 EDM. I do not know if he's made larger barrel eyepieces for observatory scopes.


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#11 25585

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Posted 13 August 2020 - 10:43 AM

100mm made for the Great Melbourne Telescope 

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#12 25585

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Posted 13 August 2020 - 10:52 AM

This could be the thread?  https://www.cloudyni...viest-ep/page-2

 

Pentax made a XL 60mm eyepiece....

https://www.cloudyni...ax-xl-60mm-r315

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Edited by 25585, 13 August 2020 - 11:15 AM.


#13 Thomas_M44

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Posted 13 August 2020 - 12:52 PM

100mm made for the Great Melbourne Telescope 

When it requires a safety vest and an assistant to swap eyepieces --then you know you've got a very serious telescope

 

Ha! 


Edited by Thomas_M44, 13 August 2020 - 12:53 PM.

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#14 ShaulaB

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Posted 13 August 2020 - 12:57 PM

A few years ago, I saw some three inch Explore Scientific eyepieces on a vendor table. They made the inch-and-a-quarter eps look like toys.

#15 dustyc

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Posted 13 August 2020 - 02:46 PM

100mm made for the Great Melbourne Telescope 

You could use both eyes to look thru that one! 


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