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Thread: 25mm Bushnell 780102 Kellner

  1. #1
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    Default 25mm Bushnell 780102 Kellner



    I recently acquired a 25mm Bushnell 780102 Kellner. I was experimenting using a 0.5x reducer on various lightweight eyepieces for using in smaller aperture highly portable Mak’s. Most small Kellners I’ve come across are not particularly that well made and have plastic or resin housings.

    IMG_20171129_204109.jpg

    Apparently the 780102 Kellner has now been discontinued, probably due to competition from other types of small eyepiece. The Bushnell Kellner is well made with good baffling and a quality volcano top housing and chromed brass drawtube. The field stop is over 20mm.

    IMG_20171129_204300.jpg

    I find that it reduces well (very slight vignetting) and can be used in conjunction with a Barlow to good effect. It gives a sharp, bright and clear well contrasted image with an alleged 45° FOV, which in a slow scope is very reminiscent of using an orthoscopic.

    Screenshot 2018-01-05 at 18.41.11.png

    I don’t know a great deal about these Bushnell eyepieces. Does anyone use any of them, if so, what are your experiences?

    b1.jpg
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    Default Re: 25mm Bushnell 780102 Kellner

    I had seen this when you posted elsewhere and thought that it was very interesting. Granted the kellner design does seem to perform better in slower/longer FL scopes. I'm interested to hear your further analysis. I do enjoy tinkering around with the no-typical accessories.
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    Default Re: 25mm Bushnell 780102 Kellner

    Quote Originally Posted by SpyderwerX View Post
    I had seen this when you posted elsewhere and thought that it was very interesting. Granted the kellner design does seem to perform better in slower/longer FL scopes. I'm interested to hear your further analysis. I do enjoy tinkering around with the no-typical accessories.
    My thinking was that an eyepiece with less lens groups would be more efficient on a smaller aperture, especially if I added a reducer.

    IMG_20171130_130449.jpg

    The inexpensive SvBony Kellner didn't vignette at all. So I tried others, the SvBony Aspheric, like the Bushnell, vignetted a tiny bit near the edges. Something I could live with anyway. The Bushnell with the reducer gives me 25x on my 90mm Orion StarMax. I get a 3.6mm exit pupil and a one arc degree, forty eight minutes of TFOV.

    This enables me to use a broadband filter like the Baader UHC-S or Orion SkyGlow on objects such as M42 on a small portable Mak.

    The Bushnell also Barlows well and is good for mid-power lunar viewing. I've been told that they're ideally used on scopes of f/8 and slower. I'll experiment further lol.
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    Default Re: 25mm Bushnell 780102 Kellner

    Hello Shorty Barlow,

    and thank you for introducing the Kellner eyepieces.

    During the Holiday Seasons, I have retrieved the Carl Zeiss Jena (CZJ) A 12.5x (f=20mm) classic Kellner (1-2), I have been using on the faint fuzzies still 20 years ago.
    The Kellner design, manufactured by CZJ for the faint fluorescence microscopy, is excellent suited for the low surface brightness and low contrast faint fuzzies, and the CZJ Kellner beats eventually even the Abbe orthos on some deep sky objects.

    The attached pic shows at right the CZJ A 12.5x (f=20mm) Kellner on the telelens-to scope adapter for the medium format (6cmx6cm) Pentacon telelenses I have been using in past as the grab-and-go telescopes.

    My generation has grown up with the Kellner and other microscope eyepieces, both on the availability and budget reasons.
    Unfortunately, the CZJ Kellner eyepieces have been forgotten,

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    Default Re: 25mm Bushnell 780102 Kellner

    Quote Originally Posted by j.gardavsky View Post
    Hello Shorty Barlow,

    and thank you for introducing the Kellner eyepieces.

    During the Holiday Seasons, I have retrieved the Carl Zeiss Jena (CZJ) A 12.5x (f=20mm) classic Kellner (1-2), I have been using on the faint fuzzies still 20 years ago.
    The Kellner design, manufactured by CZJ for the faint fluorescence microscopy, is excellent suited for the low surface brightness and low contrast faint fuzzies, and the CZJ Kellner beats eventually even the Abbe orthos on some deep sky objects.

    The attached pic shows at right the CZJ A 12.5x (f=20mm) Kellner on the telelens-to scope adapter for the medium format (6cmx6cm) Pentacon telelenses I have been using in past as the grab-and-go telescopes.

    My generation has grown up with the Kellner and other microscope eyepieces, both on the availability and budget reasons.
    Unfortunately, the CZJ Kellner eyepieces have been forgotten,

    JG
    The CZJ Kellner looks really nice, a collector's item now I reckon lol. I was surprised how sharp the Bushnell was, even compared directly to an orthoscopic, at low and medium magnifications. It was still as sharp and clear as an Astro Hutech 25mm ortho' when viewing the Moon at 80x and 100x when used in conjunction with a Barlow in a small Maksutov.
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    Default Re: 25mm Bushnell 780102 Kellner

    I think Kellners are a crap-shoot. I've looked through some pretty good ones, but also some horrible ones. There was even a big disparity in the quality of vintage Celestron, Japanese-made Kellners that came with the old C-8 SCTs.
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    Default Re: 25mm Bushnell 780102 Kellner

    Well as mentioned there are good Kellner's and there are bad ones , the ones sold with modern cheap scopes certainly qualify for bad , I recently got a 130 Skyprodigy Celestron scope that came with a 9 and 25mm Kellner's I don't have the scope anymore(used by my grand kids) but was shocked that a relatively expensive fast scope came with them , simple GSO Plossll gave much better view. with the .965 format I have a 12mm that came with the Tasco 10TE but a 12mm Orthos that I purchased works much better, lot more eye relief and less coma
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    Default Re: 25mm Bushnell 780102 Kellner

    Quote Originally Posted by Arctic View Post
    I think Kellners are a crap-shoot. I've looked through some pretty good ones, but also some horrible ones. There was even a big disparity in the quality of vintage Celestron, Japanese-made Kellners that came with the old C-8 SCTs.
    There certainly are a lot of poor Kellners still around. A lot of the giveaway eyepieces included with Sky-Watcher scopes are reversed Kellners.

    IMG_20150919_195711.jpg

    Most have plastic housings, you can tell they aren't normal Kellners as they have convex eye lenses.

    IMG_20150917_144416.jpg
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    Default Re: 25mm Bushnell 780102 Kellner

    Quote Originally Posted by 12richardk View Post
    Well as mentioned there are good Kellner's and there are bad ones , the ones sold with modern cheap scopes certainly qualify for bad , I recently got a 130 Skyprodigy Celestron scope that came with a 9 and 25mm Kellner's I don't have the scope anymore(used by my grand kids) but was shocked that a relatively expensive fast scope came with them , simple GSO Plossll gave much better view. with the .965 format I have a 12mm that came with the Tasco 10TE but a 12mm Orthos that I purchased works much better, lot more eye relief and less coma
    Speaking of dodgy Kellners given away with scopes.

    IMG_20150919_200122.jpg

    I think these qualify for that.
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