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21 RKE vs 20 TeleVue Plossl in binoviewers - any thoughts?

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#1 CrazyPanda

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Posted 21 September 2021 - 11:29 AM

For my binoviewer setup, something in the 20-21 focal length range would end up being my "high power" eyepiece, which would present approximately 400-500x in my scope. Nights that I can use that magnification are rare, but the past few observing sessions would have benefitted from that kind of magnification.

 

Given the stock issues with the 20mm TV Plossls, I've also be considering the 21 Edmund RKEs.

 

Has anyone done any comparisons between the two either mono or binoviewing?

 

(note that anything below 20mm is just too much magnification for my setup, else I'd be looking at some 18 abbe Orthos or 18.2 DeLites. Above this I have a pair of 25mm Zeiss E-PLs that I love).


Edited by CrazyPanda, 21 September 2021 - 11:30 AM.


#2 Nippon

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Posted 21 September 2021 - 11:42 AM

I have a set of the RKEs and used to have TV Plossls in 32, 15, and 11mm. I prefer the RKEs for a couple of reasons. The TV Plossls darken near the edges of the field. I read why a long time ago but don't remember. But why ever they do that I didn't like it. The other reason is the RKEs do not have undercuts and the TVs do and I hate undercuts. I find the RKE's to be just as good as far as sharpness and contrast. Despite what Edmund says about the AFOV the RKEs  are 50 degrees not the claimed 45 degrees. The TVs seem a little sharper at the extreme edge but I don't know if that is just an illusion caused by the aforementioned darkening at the edge of the TV Plossls field of view or actually better edge correction.


Edited by Nippon, 21 September 2021 - 11:44 AM.

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#3 j.gardavsky

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Posted 24 September 2021 - 10:07 AM

For my binoviewer setup, something in the 20-21 focal length range would end up being my "high power" eyepiece, which would present approximately 400-500x in my scope. Nights that I can use that magnification are rare, but the past few observing sessions would have benefitted from that kind of magnification.

 

Given the stock issues with the 20mm TV Plossls, I've also be considering the 21 Edmund RKEs.

 

Has anyone done any comparisons between the two either mono or binoviewing?

 

(note that anything below 20mm is just too much magnification for my setup, else I'd be looking at some 18 abbe Orthos or 18.2 DeLites. Above this I have a pair of 25mm Zeiss E-PLs that I love).

Hi,

 

the 21mm RKEs are certainly a very good choice, and not breaking the bank.

 

The f=20mm eyepieces are in my current arsenal underrepresented,

the best one is the Leica HC 12,5x/16 Plan M #506515, f=20mm, AFOV 45°,

with its lenses sequence (1 - field stop - 2 - 1 - 1) concave concave out, a bit oversophisticated. With its intrafocal design and internal focusing (M) on the field stop, I can play to get the best performance across the field, whenever I have "Lust" to do it. The field stop is not fringing.

 

I have also the Carl Zeiss S-Pl 12,5x/16 #44 40 49 f=20mm, but somehow my eyes prefer the Leica.

 

The third one is the old Swarovski 22x Habicht f=20.9mm AFOV 55°, not bad either, but the adapters to 1.25" are as good as unavailable.

 

Wishing you the best choice,

JG


Edited by j.gardavsky, 24 September 2021 - 10:08 AM.

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#4 kroum

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Posted 24 September 2021 - 10:51 AM

Not that this will help much since they are not currently on sale , but I adore my 20mm “Sterling” (Long Perng) Plossls pair in my binoviewer. 

Excellent contrast, sharpness, and perfect eye relief (for me personally anyway).  They are also slightly wider than other plossls at 55-57degrees AFOV.

In my f4.9 reflector, with a 1.6x OCA, (~f8 effectively), they are sharp to the field stop.



#5 Highburymark

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Posted 27 September 2021 - 06:58 PM

Not used the RKEs. I have TV plossl 20mm pair (never seen any edge darkening) and Delite 18.2s, which are beautiful. But I can’t help asking why your lovely E-PLs couldn’t fill that gap with a 1.25x gpc or some other limited barlow? I have a pair of Zeiss microscope eps (also 25mm) that I barlow up to silly magnifications with GPCs and AP barcon. Works very nicely

#6 Tank

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Posted 27 September 2021 - 07:39 PM

Had both
Liked the TV plossl a bit better for star color saturation POP
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#7 naramsin

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Posted 01 October 2021 - 09:28 PM

The older 21mm TV plossls are sublime (IMHO).

 

The 18.2mm Delites are even better.

 

Not relevant by I'm really fond of my 28mm RKEs.

 

I use all as pairs in BVs.


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#8 CrazyPanda

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Posted 01 October 2021 - 10:58 PM

Not used the RKEs. I have TV plossl 20mm pair (never seen any edge darkening) and Delite 18.2s, which are beautiful. But I can’t help asking why your lovely E-PLs couldn’t fill that gap with a 1.25x gpc or some other limited barlow? I have a pair of Zeiss microscope eps (also 25mm) that I barlow up to silly magnifications with GPCs and AP barcon. Works very nicely

The barlow I use is the APM 2.7x coma correcting barlow, so I wouldn't be using any other barlow or GPC with it.

 

So I'm trying to fit some eyepieces around it.



#9 Kunama

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Posted 02 October 2021 - 01:15 AM

These are excellent…. https://agenaastro.c...piece-21mm.html

 

21mm

65degree

sharp

18mm eye relief


Edited by Kunama, 02 October 2021 - 01:17 AM.

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#10 CrazyPanda

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Posted 02 October 2021 - 02:25 AM

These are excellent…. https://agenaastro.c...piece-21mm.html

 

21mm

65degree

sharp

18mm eye relief

Hmm I forgot those existed. Decisions decisions.



#11 25585

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Posted 02 October 2021 - 05:48 AM

The older 21mm TV plossls are sublime (IMHO).

 

The 18.2mm Delites are even better.

 

Not relevant by I'm really fond of my 28mm RKEs.

 

I use all as pairs in BVs.

I use pair of 28s binoing, excellent!


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#12 GOLGO13

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Posted 03 October 2021 - 08:27 AM

Probably 7-8 years ago I bought a 21.5 RKE new from the company that currently sells them. It was a great eyepiece. It doesn't get as much press as the 28mm, but I can say they are quite good.



#13 lylver

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Posted 03 October 2021 - 11:04 AM

I owned some RKE, I am happy they made a new batch of them, simple and efficient design, volcano eyecup well adaptated, the reflexion on eye is less annoying than the concave TeleVue : you won't regret it.


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