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An Old Kellner vs. a New Plossl

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#1 bumm

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Posted 19 October 2014 - 01:07 AM

For the last 37 years, I've been cruising the night sky from western Iowa using my old orange C8 SCT with a gaggle of old Celestron Kellners.  My only "classier" eyepiece is a 5mm Celestron Orthoscopic, but the nights are seldom steady enough to make that one useful, and I'm pretty much a dim fuzzy chaser anyway.  Occasionally, I've felt twinges of eyepiece fever, but I'm somewhat isolated out here, and haven't ever run across someone out in the dark saying "Here, slip this Tele Vue in and take a look with that."  Some years ago, I brought it up in the old sci.astro.amateur group, and was told that back when I bought these things, many Kellners were made with higher quality, and could be quite good.  I stuck with them, but still, I sometimes wondered...

     Last week, I started digging around online and reading reviews, and discovered GSO Plossls.  These were a very economical Chinese made eyepiece, but had very good reviews.  I put some stock in these reviews, because these GSO's lacked the snob appeal that can add something of a "placebo effect" to more illustrious examples costing ten times as much.  I ordered a 25mm GSO Plossl to match my old Celestron 25mm Kellner, and waited with some anticipation for the chance to compare them.  I had no emotional stock in the outcome.  While maybe I sort of hoped I'd see a big improvement over my old Kellner, I can get some cantankerous enjoyment out of using outmoded old stuff.

     Tonight turned out to be the night.  My new Plossl arrived yesterday, and tonight the sky was clear of clouds with at least average transparency.  I put my new 25mm Plossl next to my old 25mm Kellner in the turret, set them parfocal, and went out to take a look.

     My first target was NGC 247 in Cetus.  It's a rather low surface brightness galaxy  that I figured might be a good test.  This galaxy always looks rather "cometary" to me, with it's southern end containing a brighter field star.  I found the galaxy in my 40mm eyepiece and then clicked up to my old 25mm Kellner...  The transparency was nothing to get excited about, but the galaxy was visible as a bit of flare rising north off of that field star.  I clicked up to the 25mm Plossl, and there it was again...  Was it clearer?  I couldn't really tell...  I flipped back and forth, refocussing each eyepiece to give neither any advantage.  Did the Plossl have a slightly wider FOV...?  Maybe...  But did the galaxy show a bit clearer in the old Kellner?  I was looking through one less piece of glass with that one, but I'd also been rubbing my eye on it for 37 years...  Was the Plossl maybe easier to look through?  Maybe...

     I swung my scope down to NGC 253, the famous "Silver Dollar Galaxy."  It showed in the old Kellner as a mottled oval, almost hinting at resolution which I knew was really impossible.  I switched up to my new Plossl...  a mottled oval again...  I focused on the two field stars blow it and let it drift across the FOV...  Then I switched back down to the Kellner...  I focussed again on the pair of field stars...  I switched back and forth and back and forth several times...

     I swung down a little farther to view the globular cluster NGC 288...  I'd seen this one for  the first time just last week.  It showed as a slightly ragged looking cluster with hints of darker areas inside...  I couldn't resolve it into stars, but it's very low in the sky for me, and like I said, the transparency wasn't the greatest...  Again, I switched back and forth between the two 25mm eyepieces, looking for differences.  MAYBE the Plossl had a SLIGHTLY wider FOV, but nothing for sure...

     For a change, I swung up to the Pleiades.  I generally consider them more of a binocular cluster than telescopic, but I'd see what happens...  I first looked at the little string of stars that kind of trail down behind them...  Galileo drew those.  Again, I switched back and forth and back and forth, looking to see if either eyepiece would show more stars, or a clearer view.  MAYBE the Plossl had a SLIGHTLY wider FOV, but not by much, and both eyepieces seemed pretty sharp to the edges, at least to my eye...  I moved to the center of the beautiful cluster to check out the three little companions ahead of Alcyone...  Again, no real difference.  I swung down below Merope, looking for hints of nebulosity, but tonight neither eyepiece gave much indication of anything  there.  I was observing through moderate light pollution, but that's real life...

     I swung the scope back down south and checked out NGC's 247 and 253 again...  No real winner between the two eyepieces.  The temperature was just over 40, and my fingers were getting cold.  I unbolted my scope, broke down my tripod and came back in.  I went out wondering if I'd send in for one or two new eyepieces tomorrow, but so far, I see no reason to.  Some in here would say save up and buy some BETTER eyepieces, and they may be right.  This experiement isn't over, and I'm sure I do the same thing on some future night with more impressive transparency, but at this point, I'm happy with my old Kellners.  Would I suggest to anyone that they should stock up on Kellners?  No.  There's probably truth in the statement that most modern Kellners are made with low quality to throw in with new scopes.  My F10 SCT may be more forgiving of the simple Kellner than faster Newtonians too.  But just maybe there's some advantage in looking through only three pieces of glass, too.

     Like I said, I'll try this experiment again sometime, but I feel no urge right now to start sending in for more eyepieces.

                                                                                                                       Marty

 

 


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#2 optinuke

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Posted 19 October 2014 - 01:27 AM

Marty,

 

Interesting report.  I enjoy using my old Kellners as well as some more complex designs. 

 

Especially satisfying in a retro kind of way is spying a faint moon/star/Pluto through my C14 and a peanut-of-an-eyepiece Kellner.

 

I look forward to your future reports.

 

Jay



#3 bumm

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Posted 19 October 2014 - 02:06 AM

One more thought...  The new GSO eyepiece had a little rubber eyeshield that I really appreciated.  My old Kellners actually have a beveled shape round the lens, letting in more light pollution.  I found myself holding my hand up to shade my eye from the surrounding imperfect world to make a fair comparison between the two eyepieces.  ALL my night binoculars get winged eyeshields.  I think it's more practical for a telescope eyepiece to have a simple ring shield, but if nothing else changes after this experience, I'll probably wind up finding simple rubber eyeshields for my old Kellners. :)

                                                                                            Marty


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#4 hottr6

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Posted 19 October 2014 - 09:52 AM

I like Kellners in my slower 'scopes.  Sharp, easy to use and no balance problems.  Like the OP, most of my Kellners (6mm-60mm) are older Tanis or Vixens, and their only real downside is the lack of good/modern coatings.

 

Some years ago I picked up some Japan-made Kellners from Sheldon Faworski that do have more modern coatings, and the difference between old and new is significant on the brighter planets.

 

I believe that Kellner optics with modern coatings in a well-designed housing with a machined field stop and stray-light mitigation would appeal to many observers.


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#5 GOLGO13

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Posted 19 October 2014 - 10:08 AM

I recently did a comparison of 25mm eyepieces and the Kellner did very well. It's a Japanese volcano top Celestron Kellner, so a pretty nice one. I compared it to a Japanese volcano top University Optics Ortho and a Televue Plossl.

 

I used a pretty fast scope (Televue 60mm F6). The field of view was the biggest difference probably...the kellner having the smallest. The edges in the Kellner were not as sharp as the other two, but not bad.

 

Overall though I think I liked the Kellner from a comfortable view perspective. I was only observing star clusters so not sure what the verdict would be on Jupiter. I plan to do the same comparsion on that and the Orion nebula.

 

I do find some of the lower numbered Kellners to have too restrictive of field of views, and I am a small field of view kind of guy.

 

I am also a huge fan of RKEs and have two sets of them (for bino-viewing).



#6 penguinx64

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Posted 19 October 2014 - 04:24 PM

Nice report.  Thanks!  I tried a 25mm Celestron volcano top Kellner and it had a nice sharp view.  Slightly sharper than a 25mm Orion Sirius Plossl but a 26mm Meade Super Plossl had a slightly wider field of view.  Which is better?  It's hard to tell.  My only complaint is the Celestron Kellner was hard to focus.  I had to pull it out of the eyepiece holder about 1/2 inch to make it work.  Not even a little bit parafocal.  But once I tweaked it and got it focused, it worked great.



#7 bumm

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Posted 19 October 2014 - 04:41 PM

Nice report.  Thanks!  I tried a 25mm Celestron volcano top Kellner and it had a nice sharp view.  Slightly sharper than a 25mm Orion Sirius Plossl but a 26mm Meade Super Plossl had a slightly wider field of view.  Which is better?  It's hard to tell.  My only complaint is the Celestron Kellner was hard to focus.  I had to pull it out of the eyepiece holder about 1/2 inch to make it work.  Not even a little bit parafocal.  But once I tweaked it and got it focused, it worked great.

 

Both you and Golgo13 referred to Celestron "volcano top" Kellner's, and that's what I evidently have...  I was calling it "beveled," but I obviously haven't spent much time in this section of Cloudy Nights.  :)  And, like you say, my eyepieces aren't AT ALL parfocal.  I use a turret though, and just set the set screws with each eyepiece in the same focus.  My only problem with the "volcano top" shape, is, as I mentioned above, the increased difficulty in blocking out surrounding light pollution.  I sent away for a set of soft rubber eyepiece shields this morning, and I'm expecting to like 'em.  I've always put the "wing" type of eyeshields on all of my nighttime binoculars, (which makes a HUGE difference,) but I've never bothered with my telescope eyepieces.  The ones I ordered are simple symmetrical ones though, that should work better with telescope eyepieces.


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#8 zeehas

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Posted 20 October 2014 - 09:01 PM

A while back, on a whim, I decided to compare my old University Optics 9mm Kellner with the 9mm Celestron Plossl that was thrown in with their 4" f/10 refractor. The target was Mars and the scope was the 4" f/10. The UO Kellner undoubtedly had the superior fit and finish, with its nicely machined volcano top. I believe it has simple MgFl coatings. The Plossl was multicoated with the rubber eyeguard. Anyway, a critical look at Mars had me convinced that the newer Plossl easily showed the most detail.  The Kellner suffered from lateral chromatic aberration, ghosting, and a generally softer view. That's too bad since, for a long time, it was one of my most used eyepieces. I just never had anything better to compare it to. I wound up giving it away to a friend who only had 2 oculars.

 

On the other hand, I will say that I have yet to try anything that compares well with the old 7mm UO orthoscopic that's been in my collection just as long.

 

I should also emphasize that this comparison involved relatively short focal length eyepieces used in high power planetary observation. It doesn't necessarily apply to the use of Kellners at medium to low powers. They may indeed be perfectly adequate in other power ranges and types of viewing. I particularly enjoy the views in my RKE 28mm (a modified Kellner).


Edited by zeehas, 20 October 2014 - 11:52 PM.


#9 Pollux556

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Posted 24 October 2014 - 01:51 PM

I have a complete line of volcano top Kellner.  I often compared those EP with TV Plössl in my slower scope.   The only negative thing I found was the ghost image when I pointed bright objet.

 

 

 

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#10 hottr6

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Posted 24 October 2014 - 02:22 PM

I have a complete line of volcano top Kellner.

 

Well, maybe a complete line of 1.25" VTs....

IMG_5279.JPG



#11 Pollux556

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Posted 24 October 2014 - 02:27 PM

 

I have a complete line of volcano top Kellner.

 

Well, maybe a complete line of 1.25" VTs....

 

 

:crazy:  :ubetcha: 

 

Nice eyepiece.

 



#12 dcx3420

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Posted 24 October 2014 - 06:38 PM

I too have a bunch of older Celestron volcano top kellners that were made in Japan circle T's. I would rate them as good as any TV plossls I have fov a little smaller, but nonetheless very nice ep's  I also have a Celestron 20mm er circle T it has a threaded top for a filter, actually I got a moon filter to go with it. probably time to part with these and let someone else enjoy them.

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#13 astrodon

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Posted 24 October 2014 - 07:53 PM

That 20mm Circle T Er with the threaded top is cool!



#14 dcx3420

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Posted 24 October 2014 - 08:00 PM

Thank you, I never use filters but this looked so good I could not pass up posting it. At first I thought the threads on top were ridges to keep out stray light. Then I decided to see if the moon filter that came with it would screw in, it fits like a glove.

 

Gary


Edited by dcx3420, 24 October 2014 - 09:08 PM.


#15 hottr6

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Posted 25 October 2014 - 09:23 AM

The Er20mm (I don't know about the threaded version) is also a worthy keeper.  In my longer 'scopes, it easily compares favorably with the much more modern Meade 5000 20mm SWA, and is surprisingly well-corrected in fast Newts.  I do find the Er32mm to be the "clunker" of the Tani series and I could never feel the love and sold it.  I've never tried the Er16mm, but I am on the lookout for one.



#16 dcx3420

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Posted 25 October 2014 - 10:58 AM

hottr6, do you have a Celestron Er. 20mm circle T. I am wondering if all of these have the threaded tops or ridges. 

 

Gary


Edited by dcx3420, 25 October 2014 - 10:58 AM.


#17 hottr6

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Posted 27 October 2014 - 11:45 AM

hottr6, do you have a Celestron Er. 20mm circle T. I am wondering if all of these have the threaded tops or ridges. 

 

Well, make a fibber of me.  I dug out this eyepiece and it does have the threads cut into the top.  I have never noticed them before and if I had, I would have thought they were for stray- light mitigation.  On closer inspection, I also discover that it is a Double-Circle-V, not Tani.  The first thing to suffer when one hits old age is memory loss, and I forget the second thing!  :lol:

 

IMG_5542.jpg

IMG_5543.jpg



#18 dcx3420

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Posted 27 October 2014 - 03:53 PM

Hmmm. Interesting that there were two Co.s making the same ep. Either way both are great ep's. Thank you for digging it out...I thought the circle T meant Towa, but say Tani?

 

Regards Gary



#19 hottr6

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Posted 28 October 2014 - 10:11 PM

I thought the circle T meant Towa, but say Tani?

 

That's what I thought until corrected by vintage CNers.  Circle-T on telescopes mean Towa, Circle-T on eyepieces mean Tani.  Confused yet?  ;)



#20 dcx3420

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Posted 29 October 2014 - 11:41 AM

 

I thought the circle T meant Towa, but say Tani?

 

That's what I thought until corrected by vintage CNers.  Circle-T on telescopes mean Towa, Circle-T on eyepieces mean Tani.  Confused yet?  ;)

 

Very:) So who made the Double-Circle-V ep's


Edited by dcx3420, 29 October 2014 - 11:43 AM.


#21 Certochrom

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Posted 21 October 2015 - 01:47 PM

Some weeks ago, I could get a 12mm Tani volcanotop Kellner in perfect condition. They are very hard to find here in Europe, I got this piece from the U.S. westcoast:

 

DSC08859a

 

 

This Kellner shows perfect sharpness all over the FOV, I am very pleased with this one. Really good Kellners show almost no difference to orthos, but they sometimes show ghost images. My 12mm Kellner has shown such one so far only when viewing the full moon. My Kellner 12mm definitely shows better performance than a 12mm Plössl of modern production.

 

This Kellner seems be sold with a Coulter Optical scope, maybe the Voss 8" Cassegrain. At least, these were offered with three Kellner achromats in 40mm, 12mm and 6mm.

 

Sadly enough, all newer Kellner eyepieces I know, are of poor quality and have let to a bad reputation of this great design.

 

Michael


Edited by Certochrom, 21 October 2015 - 02:51 PM.

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#22 BillP

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Posted 21 October 2015 - 03:15 PM

Great report Marty :waytogo:



#23 daniel_h

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Posted 21 October 2015 - 04:20 PM

i often use cheap kellner's in my f12 frac, to be honest they show nice dark backgrounds & very nice star points -they are also surprisingly good on dso's  lunar; minimal glass & long f/l scope are a good combo


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#24 jgroub

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Posted 21 October 2015 - 04:57 PM

i often use cheap kellner's in my f12 frac, to be honest they show nice dark backgrounds & very nice star points -they are also surprisingly good on dso's  lunar; minimal glass & long f/l scope are a good combo

Love Kellners on long focal ratio scopes.  It's interesting; my scope, the NexStar 127 Mak, comes with 9mm and 25mm Kellners instead of Plossls.  Of course, Celestron is just doing this to save a couple of bucks.  But it's actually a blessing in disguise - the Kellners work great on the f/12 Mak.  Nice lunar and planetary views. 


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#25 JIMZ7

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Posted 21 October 2015 - 05:06 PM

Last time I looked Agena was selling GSO Plossls from Taiwan not China. But anyways I use to have a flat-top Celestron 20mm Kellner from Japan. At the same time I had a Meade RG 20mm Erfle. Both very sharp but of course the Erfle had a 70 degree fov vs maybe 40-42 for the Kellner. It was hard to decide which to keep & to sell. The Erfle won out but the Kellner was very sharp and showed Jupiter pure white to me. The stars were pinpoint across the fov view in my late 1950's 60mm Montgomery Wards 700mm fl. refractor. I hated to part with it but 70 degree fov was not a hard decision to make in a small scope.

 

Jim  


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