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Equipment Discussions >> Eyepieces

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BillStar
Pooh-Bah


Reged: 07/29/10

Loc: Connecticut & North Carolina
32mm RKE wide angle Erfle?
      #4308376 - 01/11/11 10:39 PM

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

http://www.anchoroptics.com/catalog/product.cfm?id=193

Comments?
Caveats?
Criticisms?


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gnowellsct
Postmaster
*****

Reged: 06/24/09

Re: 32mm RKE wide angle Erfle? new [Re: BillStar]
      #4308534 - 01/12/11 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


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? new [Re: BillStar]
      #4308560 - 01/12/11 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.edmundoptics.com/onlinecatalog/displayproduct.cfm?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


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gnowellsct
Postmaster
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Reged: 06/24/09

Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #4309059 - 01/12/11 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


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psu_13
sage


Reged: 05/30/10

Re: 32mm RKE wide angle Erfle? new [Re: gnowellsct]
      #4309080 - 01/12/11 09:50 AM

I recall reading this...

http://www.astromart.com/articles/article.asp?article_id=793


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BillStar
Pooh-Bah


Reged: 07/29/10

Loc: Connecticut & North Carolina
Re: 32mm RKE wide angle Erfle? new [Re: psu_13]
      #4309166 - 01/12/11 10:36 AM

Quote:

I recall reading this...

http://www.astromart.com/articles/article.asp?article_id=793



Thanks,
That's a surprising report.

Bill


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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: 32mm RKE wide angle Erfle? new [Re: BillStar]
      #4309283 - 01/12/11 11:40 AM

Quote:

Quote:

I recall reading this...

http://www.astromart.com/articles/article.asp?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


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? new [Re: dan_h]
      #4309350 - 01/12/11 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.

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

- Jim


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 32mm RKE wide angle Erfle? new [Re: BillStar]
      #4309358 - 01/12/11 12:13 PM

Quote:

Quote:

I recall reading this...

http://www.astromart.com/articles/article.asp?article_id=793



Thanks,
That's a surprising report.

Bill




I suggest not trading in that 31mm Nagler.

Jon


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? new [Re: Jon Isaacs]
      #4309362 - 01/12/11 12:17 PM



- Jim


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Bob Myler
Pooh-Bah
*****

Reged: 05/18/06

Loc: St Louis, MO
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #4310559 - 01/12/11 09:47 PM

Quote:

"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.edmundoptics.com/onlinecatalog/displayproduct.cfm?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.


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GaryJCarter
sage
*****

Reged: 06/06/09

Loc: Fairview, Texas
Re: 32mm RKE wide angle Erfle? new [Re: Bob Myler]
      #4310965 - 01/13/11 02:06 AM

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

http://www.astromart.com/classifieds/details.asp?classified_id=698284


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JIMZ7
Pooh-Bah
*****

Reged: 10/22/05

Loc: S.E.Michigan near DTW
Re: 32mm RKE wide angle Erfle? new [Re: GaryJCarter]
      #4311219 - 01/13/11 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


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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: 32mm RKE wide angle Erfle? new [Re: JIMZ7]
      #4311694 - 01/13/11 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.

Edited by drollere (01/13/11 03:50 PM)


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? new [Re: GaryJCarter]
      #4311980 - 01/13/11 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.com/articles/article.asp?article_id=793

- Jim

Edited by jrbarnett (01/13/11 02:40 PM)


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? *DELETED* new [Re: drollere]
      #4312007 - 01/13/11 02:48 PM

Post deleted by jrbarnett

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Mike Hosea
Postmaster
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Reged: 09/24/03

Loc: "Metrowest" Boston
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #4312133 - 01/13/11 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).

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Mike Hosea
Postmaster
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Reged: 09/24/03

Loc: "Metrowest" Boston
Re: 32mm RKE wide angle Erfle? new [Re: drollere]
      #4312502 - 01/13/11 06:23 PM

Quote:


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.


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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #4314464 - 01/14/11 03:54 PM

Quote:

"It comprises 3 achromats and is tack sharp."




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


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 32mm RKE wide angle Erfle? new [Re: drollere]
      #4314643 - 01/14/11 05:20 PM

Quote:

Quote:

"It comprises 3 achromats and is tack sharp."




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






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


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bdcmd
sage
*****

Reged: 03/14/08

Loc: Glen Rose, Texas
Re: 32mm RKE wide angle Erfle? new [Re: Jon Isaacs]
      #4315157 - 01/14/11 10:11 PM

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

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Mark Swanson
member
*****

Reged: 03/09/07

Loc: Irving, Tx
Re: 32mm RKE wide angle Erfle? new [Re: GaryJCarter]
      #5546296 - 11/29/12 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.

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Mark Swanson
member
*****

Reged: 03/09/07

Loc: Irving, Tx
Re: 32mm RKE wide angle Erfle? new [Re: Jon Isaacs]
      #5546315 - 11/29/12 09:45 PM

Who asked you?

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Mark Swanson
member
*****

Reged: 03/09/07

Loc: Irving, Tx
Re: 32mm RKE wide angle Erfle? new [Re: dan_h]
      #5546337 - 11/29/12 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?


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GOLGO13
Carpal Tunnel


Reged: 11/05/05

Loc: St. Louis area
Re: 32mm RKE wide angle Erfle? new [Re: Mark Swanson]
      #5546656 - 11/30/12 04:36 AM

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

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BillP
Postmaster
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Reged: 11/26/06

Loc: Vienna, VA
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #5547091 - 11/30/12 12:18 PM

Quote:

"RKE" stands for "Rank Kellner Eyepiece". It is pretty much a standard Kellner reversed.




Rank, Kaspereit, Erfle, per filing for the RKE trademark ( click on document called UNCLASSIFIED ). Plus, when you look at a standard Kellner design it is a plano-convex doublet followed by a convex-plano singlet. And RKE is a double-convex singlet, followed by a convex-concave doublet. So both groups use different curve directions than the Kellner. When you look at the field doublet in an RKE, it is the same configuration as the field doublet in an Erfle or a Kaspereit design. The Kaspereit was developed from the Erfle. The upper 2 doublets of the Kaspereit are both double convex doublets. So the RKE is like removing one of those doublets, and replacing the other with a same curved singlet. So overall, looks much more like a hybrid of the Erfle and Kaspereit designs than it does at all like a reversed Kellner at all. The only common thing between the RKE and the Kellner is that they both are 3 elements in a 2-1 (or 1-2) configuration. The curves are all wrong between them, unlike the Erfle and Kaspereit.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? new [Re: BillP]
      #5547123 - 11/30/12 12:34 PM

Yes, but we didn't know about that document in early 2011, and have discussed it subsequently in a different thread, after the post you're responding to.

- Jim


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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #5547136 - 11/30/12 12:42 PM

Quote:

"It is sharper on axis than any plossl, 1RPD, Proxima,etc.."




Damning with faint praise?

Mike


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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: 32mm RKE wide angle Erfle? new [Re: Sarkikos]
      #5547161 - 11/30/12 12:53 PM

http://www.astromart.com/articles/article.asp?article_id=793

"There is a place for all of these designs. It depends on what you want out of your set of eyepieces."

I wonder if that includes Televue designs as well?

Mike


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BillP
Postmaster
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Reged: 11/26/06

Loc: Vienna, VA
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #5547322 - 11/30/12 02:29 PM

Quote:

Yes, but we didn't know about that document in early 2011, and have discussed it subsequently in a different thread, after the post you're responding to.

- Jim




OMG...look how old that post was. My bad! I never check the dates and assume posts are relatively recent. Sorry I missed that

btw, you still have the 1 RPD? I need a pic of it


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Mark Swanson
member
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Reged: 03/09/07

Loc: Irving, Tx
Re: 32mm RKE wide angle Erfle? new [Re: Sarkikos]
      #5547911 - 11/30/12 09:28 PM

Yes. Televue too. I don't think that you have to pay Televue and Pentax prices to get good glass. However, I am all for free enterprise.

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Mark Swanson
member
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Reged: 03/09/07

Loc: Irving, Tx
Re: 32mm RKE wide angle Erfle? new [Re: BillP]
      #5547915 - 11/30/12 09:29 PM

I no longer have the 1RPD. No pics either.

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Dave Ittner
sage
*****

Reged: 05/29/12

Loc: SF Bay Area, California
Re: 32mm RKE wide angle Erfle? new [Re: Mark Swanson]
      #5548072 - 11/30/12 11:52 PM

what is the 1RPD?

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 32mm RKE wide angle Erfle? new [Re: Dave Ittner]
      #5548111 - 12/01/12 12:24 AM

"1 revolution per day"

A rebrander of Chinese eyepieces, sold through Astrobuffet. Basically the same eyepiece as the 30mm BW Optik UWA and others from the same maker. All are clones of a Japanese eyepiece called the "Widescan III".

1rpd ST80: http://www.astrobuffet.com/ab/30mm_vert.jpg

BW Optik: http://www.cloudynights.com/classifieds/data/17/203014-1344291783bw1-large.jpg

Widescan IIIs: http://www.astromart.com/images/classifieds/358000-358999/358231-1.jpg

Agena UWA: http://agenaastro.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e...

Very poor edge correction in fast scopes.

- Jim


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Dave Ittner
sage
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Reged: 05/29/12

Loc: SF Bay Area, California
Re: 32mm RKE wide angle Erfle? new [Re: jrbarnett]
      #5548126 - 12/01/12 12:39 AM

thanks. I learn something new every day.

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