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University Optics 2" 13mm Wide View Plossl

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#1 oddog

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Posted 31 January 2013 - 02:28 PM

I picked up this University Optics 2" 13mm Wide View Plossl from my club as I was curious about it. How is a Plossl "wide view" and why would they put into a 2" barrel? And also is looked pretty.

I tried it the other night in a Celestron ST102 (f6) and it was just a typical Plossl as near as I could tell. The eye relief was very short, I really had to cram my eyelashes onto it to see the field stop, seemed shorter than other Plossls in similar focal lengths I have tried in the past. I don't have a Plossl close to that focal length to compare so I don't know the exact apparent field of view but I am going to try to figure it out with the timing scheme. See if I can find some of that 'wide view'.

Quality of the view was fine, very Plossl-like. I probably won't be keeping this EP as it doesn't do anything my others don't do (except look good). Look for it in the bay site soon!

Anyone else have any insights/experiences with this EP or its brothers?

Tom Duncan

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#2 jrbarnett

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Posted 31 January 2013 - 02:50 PM

Well, it's like this. Back when Plossls and Symmetricals came back into vogue, amateurs had been subsisting for decades on Orthoscopics, Kellners, and worse, with the short eye relief, poorly corrected Erfle holding down the "wide field" end of the spectrum.

For a generation weened on 40-45-degree Kellners and Orthoscopics, a 50-degree eyepiece, as most Plossls were/are, was "wide field", relatively. Your "Wide View" may not be a Plossl in actuality and may have a field of view even wider than most "Plossls".

I have a 6mm UO "zebra ring" Plossl (N.S. stickered) that is a pretty fine short focal length eyepiece. That eyepiece, however, has an AFOV closer to 45 degrees than 50. It also, predictably, has uber-tight eye relief.

Regards,

Jim

#3 oddog

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Posted 31 January 2013 - 03:25 PM

So Jim what you are saying is it is likely a 'regular' Plossl formula but as Plossl's were new at the time and had a wider field of view than what observers were used to UO decided to tout it. Kinda like how multicoating was touted over regular coating in camera lenses back in the day (Pentax's "Super-Multi-Coated-Takumar" for example).

A bit of a Google search suggests Plossls became popular in the mid 1980's. The one reference to a time frame for this EP (unverified though) is late 80s/early 90's, which would suggest it was a little late to be taking that position.

I will work on getting the FOV of it.

Photo of the 0.472 field stop (knife edged but not blackened) and lens assembly below.

Tom

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#4 Starman1

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Posted 31 January 2013 - 04:15 PM

Some time in the '90s, I obtained a (12.7mm, IIRC) Plossl from UO that had no field stop in the barrel. The AFOV was so wide it was almost impossible to see the edge of the field.
Of course, as you would expect, the star images outside the center 50 degrees were, well, uh, not good. But my god was it wide! I never actually measured the field, and passed the eyepiece along. But it was called, IIRC, a Wide-View Plossl.

#5 Starman1

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Posted 31 January 2013 - 04:18 PM

With that field stop and the usual edge-of-field distortion of a Plossl, that translates to a 55 degree field of view--wide for a Plossl, but not, even at the time, a particularly wide apparent field.

#6 Jay_Bird

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Posted 31 January 2013 - 06:05 PM

This series with the green ring was offered in 1.25 and 2 inch barrels, since the 1.25 were parfocal I'm assuming the 2 inch were as well. These included a 17, a 26, I think a 21, and maybe something under 10mm too. I bought 1.25-inch 17 and 26 off CNC and used for a few years, then gave both to educator for use with cleaned up older 4.5" f/10 scope & Barlow - a good fit for these.

17 was nice in f/6 and in f/10 SCT for medium power views, enjoyed moon or Saturn with this on nights when higher powers started to fall apart.

26 had some edge falloff in short tube achro, it did not handle f/6 as well as 17, but was also very nice in SCT.

Not bad at all, but not remarkable, a parfocal series for someone interested to use like older Plossls or Ultima-type eyepieces, good image for FOV, moderate weight and size (at least in 1.25 inch!).

#7 paul m schofield

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Posted 31 January 2013 - 06:47 PM

I still have the University Optics 26mm Wide View Plossl I bought from Astronomics in 1986. Mine is 1.25", turquoise, black, and chrome, made in Japan, multi-coated, similar to the 2" in the original picture.

It is very sharp on axis but falls off pretty badly in the outer third of the field. I drift measured the field of view and it was nearly 60 degrees AFOV.

It is not a traditional Plossl, either. I took it apart for cleaning and it has six elements, so it's basically an Erfle although my 32mm Idai Erfle has much better performance but with a 50 degree AFOV.

Being new to astronomy the 26mm was my favorite ep for my first telescope, a 6" f/5 reflector. It's a good finder eyepiece and sharp at the center but it pales next to my 24mm Panoptic.

#8 Jaimo!

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Posted 31 January 2013 - 11:32 PM

Here's a shot of the 20mm 1 1/4" version...

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Jaimo!

#9 Ira

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Posted 31 January 2013 - 11:40 PM

What's the yellow object to the right in the first photo?

/Ira

#10 Mariner@sg

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Posted 01 February 2013 - 02:29 AM

What's the yellow object to the right in the first photo?

/Ira


It's this antique called a celluloid film :grin:

#11 Grava T

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Posted 01 February 2013 - 07:26 AM

I've got the 17mm and 20mm but with the Star Trak name. A little wider than a plossl from what I can tell.

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#12 Grava T

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Posted 01 February 2013 - 07:29 AM

17mm.

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