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32mm RKE wide angle Erfle?

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#1 BillStar

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Posted 11 January 2011 - 10:39 PM

:question: Has anyone used this eyepiece? How might it perform in an f/10 SCT?

http://www.anchoropt...duct.cfm?id=193

Comments?
Caveats?
Criticisms?
:shrug:

#2 gnowellsct

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Posted 12 January 2011 - 12:00 AM

It's OK if you like sea gulls. It is also the only eyepiece I ever used that totally blacked out when I put it in a barlow.

I see many better deals over on the 'mart. one of them is being offered by me.

regards
greg n

#3 jrbarnett

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Posted 12 January 2011 - 12:13 AM

"RKE" stands for "Rank Kellner Eyepiece". It is pretty much a standard Kellner reversed. Dr. Rank also designed the eyepiece you linked, allegedly, but it's *not* and RKE despite Edmund slapping "RKE" on it. It's just an Erfle. Calling an eyepiece an "RKE Erfle" is like calling an eyepiece a "Plossl Abbe Orthoscopic".

http://www.edmundopt...?productid=2074

I've been wanting to try one of these for a long time, but $225 for an Erfle always seems a little steep. I have an excellent 2" Meade 32mm Research Grade Erfle, and it cost me about $100. If you go for it, keep us posted.

Regards,

Jim

#4 gnowellsct

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Posted 12 January 2011 - 09:39 AM

They tend to sell used on Astromart for about $100 or less. I remember I didn't get a very good price for mine. It was one of my earliest 2" eyepieces. I eventually accumulated the older style Meade SWA 32mm and a UO Konig 32mm (the good old UO) which were both mid range eyepieces in their day and both outperformed the 32 erfle. (It does however look cool)

That was quite a while ago. I converted to XWs some time after that.

Greg N

#5 psu_13

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Posted 12 January 2011 - 09:50 AM

I recall reading this...

http://www.astromart...?article_id=793

#6 BillStar

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Posted 12 January 2011 - 10:36 AM

I recall reading this...

http://www.astromart...?article_id=793

Thanks,
That's a surprising report.

Bill

#7 dan_h

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Posted 12 January 2011 - 11:40 AM

I recall reading this...

http://www.astromart...?article_id=793

Thanks,
That's a surprising report.

Bill



How does a report entitled "31mm Televue Nagler versus 32mm Edmund Erfle", conclude with , "The sharpest eyepieces I have ever used in scopes that are f7 and over is the Brandon by Vernonscope."

Simply incredible.

dan

#8 jrbarnett

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Posted 12 January 2011 - 12:10 PM

Yeah, I have noticed that conventional Erfles often do very well on-axis too, but I gotta question the merits any review that casually discards the "outer 35%" of the field in a review of wide field eyepieces. You may as well use a Plossl or Ortho if you could care less about outer 35% of a 65-degree AFOV. :lol:

Of course, the Brandon "name dropping" bit at the end, like a ward against the Evil Eye, restored a little credibility, but still...

- Jim

#9 Jon Isaacs

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Posted 12 January 2011 - 12:13 PM

I recall reading this...

http://www.astromart...?article_id=793

Thanks,
That's a surprising report.

Bill


I suggest not trading in that 31mm Nagler.

Jon

#10 jrbarnett

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Posted 12 January 2011 - 12:17 PM

:lol:

- Jim

#11 Bob Myler

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Posted 12 January 2011 - 09:47 PM

"RKE" stands for "Rank Kellner Eyepiece". It is pretty much a standard Kellner reversed. Dr. Rank also designed the eyepiece you linked, allegedly, but it's *not* and RKE despite Edmund slapping "RKE" on it. It's just an Erfle. Calling an eyepiece an "RKE Erfle" is like calling an eyepiece a "Plossl Abbe Orthoscopic".

http://www.edmundopt...?productid=2074

I've been wanting to try one of these for a long time, but $225 for an Erfle always seems a little steep. I have an excellent 2" Meade 32mm Research Grade Erfle, and it cost me about $100. If you go for it, keep us posted.

Regards,

Jim


I have one wedded to the back end of an old Edmund inspection scope - now used as a finder. The combination weighs almost 3-1/2 pounds but the views are luxurious.

#12 GaryJCarter

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Posted 13 January 2011 - 02:06 AM

Apparently he wasn't all that enamored with the Edmund...

http://www.astromart...ified_id=698284

#13 JIMZ7

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Posted 13 January 2011 - 08:26 AM

I had a 32mm U.O. 2" Erfle once and it was the only eyepiece I used that saw the "black rift" through M-31 Galaxy in a 8" f/6.9 reflector in my light pollution location.

Jim

#14 drollere

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Posted 13 January 2011 - 12:41 PM

minor point of correction: the edmund "RKE" is a kaspereit, not an erfle.

the three original erfle designs are either 1-2-2 or 2-1-2 designs (two doublets, with a singlet at either the field end or the middle). taylor's historical article on inverting eyepieces lists only the 2-1-2 form, as "origin unknown"; chris lord's paper on the evolution of eyepieces is the only source i can find that lists them all. however one or another version of the erfle turns up in ray tracing eyepiece examples, for example in the zeiss "handbook of optical systems".

if you look at the schematic, the edmund is a 2-2-2 design (three doublets). that's kaspereit's "improvement", patented a few years after the erfles.

we must all marvel at the scope of action that allows marketers to retrofit the designation "RKE" (reverse kellner eyepiece, not rank kellner eyepiece) to apply to a design that has nothing to do with either rank or kellner.

oh beware, ye users of "panoptic", "plossl", "erfle", "ortho", "kellner", "RKE", "super wide", "ultra wide", "maxi wide" eyepieces. ye may not know what ye have.

#15 jrbarnett

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Posted 13 January 2011 - 02:39 PM

I dunno. He kept it for 20 years...

"I have compared this Edmund 32mm Erfle to many eyepieces over the last 20 years. It is sharper on axis than any plossl, 1RPD, Proxima,etc. It comprises 3 achromats and is tack sharp."

http://www.astromart...?article_id=793

- Jim

#16 jrbarnett

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Posted 13 January 2011 - 02:48 PM

Post deleted by jrbarnett

#17 Mike Hosea

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Posted 13 January 2011 - 03:33 PM

I had one of these for awhile for use in a 10" f/5 Teleport. I'm having hard time remembering too much about it. I remember liking it better than I expected to, much better than the 30mm Widescan II, which isn't saying a whole lot. As has been pointed out, the used prices on these weren't so bad, but that was really for a previous age, one without Meade QX's and other inexpensive 2" superwides. IMO, it's not an interesting option to try new, strictly a used-market eyepiece for < $100. I sold mine at $80 in 2004 (when they were still $225 new).

#18 Mike Hosea

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Posted 13 January 2011 - 06:23 PM

we must all marvel at the scope of action that allows marketers to retrofit the designation "RKE" (reverse kellner eyepiece, not rank kellner eyepiece) to apply to a design that has nothing to do with either rank or kellner.


Yes, they trademarked it in the late 70's. When companies do that with acronyms, they sometimes do jettison the initial meaning.

It's a side issue, but I'm not too sure exactly what RKE originally stood for. There are 3 or 4 variations that get reported on. Unfortunately, the matter has passed beyond the institutional memory of Edmund (IIRC), not that they'd be likely to say, anyway, even if they knew.

#19 drollere

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Posted 14 January 2011 - 03:54 PM

"It comprises 3 achromats and is tack sharp."


somebody should let astronomers know that tacks are not really very sharp.

#20 Jon Isaacs

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Posted 14 January 2011 - 05:20 PM

"It comprises 3 achromats and is tack sharp."


somebody should let astronomers know that tacks are not really very sharp.


:roflmao:

That's not only the funniest thing I have read in quite some time but the most perceptive as well. "Tack Sharp" is a popular cliche used to describe equipment but as you say, tacks are not very sharp.

And razors, well, they are sharp but they do not a point, a scope or eyepiece that is razor sharp might just be astigmatic. :)

Needle sharp is more appropriate but maybe the best description ASFMTS... "Atomic Force Microscope Tip Sharp."

Tips of AFM's can be as small as 2 nanometers, much smaller than an airy disk.

Jon

#21 bdcmd

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Posted 14 January 2011 - 10:11 PM

I dunno, but I'm not sure I want anything much sharper than a tack that close to my eye. . . . .

#22 Mark Swanson

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Posted 29 November 2012 - 09:33 PM

I am more enamored with the eyepiece being discussed than having someone like you put your 2 cents in. I had this eyepiece for over 20 years. I had several. I sold it to try something else and then bought the Edmund back as I grew to miss it everytime. I have had 3 different Edmund 32MM Erfles. Get over it.

#23 Mark Swanson

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Posted 29 November 2012 - 09:45 PM

Who asked you?

#24 Mark Swanson

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Posted 29 November 2012 - 09:58 PM

You asked a dumb question, but to be "polite" I will answer it. I was finished with the review of the 31 Nagler versus the 32 Edmund. I merely pointed out some other eyepieces that I have and like.

The Brandon I used was a 32mm and I have compared it to a University 32mm 1.25" Koenig in an f14.4 Questar 3.5".

It was quite a bit sharper in the Questar than the Koenig. I also compared the Brandon to a 32mm Celestron 1.25" Erfle. Again, the Brandon was obviously sharper.

I did not compare the Koenig to the Celestron Erfle. Are you some sort of PHD eyepiece reviewer who decides what is appropriate to include in a review? Exactly what is your point, other than you are probably just another Televue suck up?

#25 GOLGO13

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Posted 30 November 2012 - 04:36 AM

I don't think there was anything "polite" about your last 3 posts. :4






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