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Another RKE 28mm Question

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#1 BobH

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Posted 06 March 2013 - 06:59 AM

Based on all the praise the Edmonds RKE 28mm has received here, I have decided to get one. I'm inclined to buy new. Since these eyepieces have been around for a while, is there any difference between the earlier ones vs current production?

Thanks

#2 denis0007dl

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Posted 06 March 2013 - 08:41 AM

Yes, there is difference: newer ones have some better coatings on lenses (especially newest ones-I gave this infos from Edmund Optics), and newer models have 1,25" filter thread!

Of course, newer ones have different ensctiptions engraved vs old oned painted!

#3 oo_void

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Posted 06 March 2013 - 11:59 AM

Though I love my set of RKE's, they aren't for everyone. On my bino's, it seems that eye relief could be measured in inches, but I like the effect personally. If you can find someone with one, give a try first before you commit to a purchase.

#4 Sarkikos

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Posted 06 March 2013 - 01:50 PM

I've sold all my RKE except a recent pair of 28's that I bought new for my binoviewer.

My experience with older RKE is that their QC can vary wildly. The most frequent defect is ratty field stops full of burrs and other imperfections. I would be reluctant to purchase another used RKE, unless I was sure that the quality was decent.

Optically, I think the RKE are inferior to decent Plossls and orthos. Views of planets and the Moon seemed better - sharper - in BGO's and TV Plossls.

IIRC, BillP said that some older version RKE's were sharper than the newest version. I must have never got a hold of any from that Golden Age of the RKE's, because none of my older ones were as sharp as the newest version - and none of the newest version were as sharp as BGO's and TV Plossls.

But, nevertheless, those RKE 28's are mighty nice trick ponies. Floating in space! I don't see letting them go.

Mike

#5 azure1961p

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Posted 06 March 2013 - 09:51 PM

RKEs aren't cheap anymore I notice and they used to be bargain basement cheap - $40 or some such. I recall Mounsey liked them a lot - said they had a color white tone compared to TVs and the warmer coffee tones. He was impressed with them greatly on the moon but less on Jupiter.

Too bad QC is random as I was thinking of getting a new pair of 28s got my binos too.

Pete

#6 johnnyha

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Posted 07 March 2013 - 05:03 AM

Good luck is all I can say, and DO NOT buy them from Surplus Shed. I got a pair of 28 RKE from Surplus Shed and they were both the single worst eyepieces I have ever bought - the edges of the lenses were chipped, the glass was full of air bubbles, the spacers were loose and rattling, the field stops were fuzzy, the red rubber grip was missing... truly a complete disaster.

#7 Mariner@sg

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Posted 07 March 2013 - 07:31 AM

Surplus shed doesn't have them anymore.

#8 bcuddihee

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Posted 07 March 2013 - 09:00 AM

I have had 6 of them over the past 5 years...always selling off stuff to buy the latest and greatest...but always keep picking them back up. I have had vintage ones and newer ones and haven't had a bad one in the bunch. Luck?,,perhaps, but possible the inconsistencies have been overstated a bit. I bought my last pair new and have been delighted with them. Not selling them this time. bc

#9 smallscopefanLeo

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Posted 08 March 2013 - 01:04 AM

Luck?,,perhaps, but possible the inconsistencies have been overstated a bit.


I am wondering about this as well, hmm.. :hmmmm:

My set is one of my more prized possessions!(including the looong barlow too, which gives one oodles of back-focus in case it is needed..)

Sure, I believe that there were some lemons put out there, but I do wonder what the ratio of that really is. (I also have two Surplus Shed 28mm's in addition to a 28mm I have from a full set, and they are later ones from towards the end of the sale that came without grips, and they seem just fine to me.. not pristine, no, and they arrived a bit dusty, but otherwise not bad at all!:shrug:)


#10 Sarkikos

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Posted 08 March 2013 - 07:05 AM

Pete,

RKEs aren't cheap anymore I notice and they used to be bargain basement cheap - $40 or some such. I recall Mounsey liked them a lot - said they had a color white tone compared to TVs and the warmer coffee tones. He was impressed with them greatly on the moon but less on Jupiter.

Too bad QC is random as I was thinking of getting a new pair of 28s got my binos too.


I keep a spreadsheet of eyepieces I own and have owned, along with specs, notes and comments from myself and other observers. My notes include Mounsey's praises for the RKE.

But I think the LER are just as good or better for lunar. (I have the Smart Astronomy brand.) They have a cool tone, also. And they are less expensive than the RKE, have longer eye relief in the shorter focal lengths, and a wide AFOV, which is better corrected. They also seem at least as sharp as the RKE to my eyes.

For the most part, I've given up on RKE except for the 28's. As I said, I'd trust getting a new pair of RKE through EO rather than playing the RKE Lottery for a used pair of 28's. Think about all the clunkers that were sold through Surplus Shed. Now you get an idea about the sort of used RKE that are lurking out there. But some have said they've gotten clunkers brand new from EO. So what can you do?

I'm just speaking from my own experience. Obviously others have been more lucky buying used.

Mike

#11 Sarkikos

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Posted 08 March 2013 - 07:16 AM

By the way, my last remaining RKE are a pair of new 28's I bought direct from EO a couple years ago. Their housings are perfect, and the optics do not have any defects. I also bought a pair of new Edmund Plossl 28's from Edmund Scientific. They were likewise perfect. I still have the pair of RKE 28's. But I've sold one of the Plossls, and will probably sell the other one.

Mike

#12 johnnyha

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Posted 08 March 2013 - 07:16 AM

I'd like to mention too that the "magical floaty effect" that the 28mm RKE is so famous for is not unique. I get a very similar effect from my 32mm Brandon, perhaps even moreso. It certainly has more to do with the fl v. fov and the size of the eye lens and housing, than anything else.

#13 azure1961p

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Posted 08 March 2013 - 07:58 AM

Well Mike, putting it in another perspective, are these RKEs better than TV 32 or 26mm plossls or 25mm Abbé Ortho? I don't see the advantage in price for something so peppered with bad QC though Im trusting yours are good.

Pete

#14 Sarkikos

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Posted 08 March 2013 - 08:19 AM

Yes, my 28's are as perfect as RKE's can be. No defects in optics or body. But, no, I don't think that optically the RKE's 28's are as well-corrected as comparable focal length TV Plossls or UO Abbe Orthos, at least not in my f/5 or f/6 Newts. But the RKE 28's are worth keeping for the floating effect and for binoviewing. I even carry one of them with me when I go to my dark site. In any case, I wouldn't get much for them if I sold them.

Mike

#15 bcuddihee

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Posted 08 March 2013 - 09:51 AM

Pete, are the 28 rke's better than plossls or ortho? That depends on the scope, viewing preference and individual ep. In my longish fl c8 with added diagonal and bino, its pretty sharp to the edge. Different than the others..most definitely..it's a wholly different viewing experience. Both types of ep's will get you there, the perceived view will be different.

#16 Sarkikos

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Posted 08 March 2013 - 11:02 AM

AFAIK, the RKE's are merely "coated," not FMC like the TV Plossls or even FC like Brandons. These simple coatings might have something to do with the different experience which the RKE's give. Simple coatings can give a darker background and increase perceived contrast for planet features and bright nebulae and galaxies. They might also display deeper colors for bright stars.

I've decided to mostly stay away from anything less than FMC for DSO, though I still keep an RKE 28 and a couple Brandons in my deep sky case. If I want to see more contrast in nebulae, I can always put a DSO filter on an eyepiece with FMC coatings.

Mike

#17 Starman1

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Posted 08 March 2013 - 12:28 PM

AFAIK, the RKE's are merely "coated," not FMC like the TV Plossls or even FC like Brandons. Simple coatings can give a darker background and increase perceived contrast for planet features and bright nebulae and galaxies. They might also display deeper colors for bright stars.

Mike


Though multi-coatings can, indeed, produce a different spectrum of transmission than simple magnesium fluoride coatings, the different spectrum is usually a HIGHER brightness/transmission at all visible wavelengths.
On a really large curved lens, the lower the angle of viewing, the more the spectrum can change, such that the spectrum of transmission may be different if holding your eye in the center and looking toward the edge.
But eyepieces of this (RKE) diameter are not so large this spectral change is significant.
RKEs have simple coatings on the lenses to keep costs down. A small number of elements allows that (theoretical 94% transmission).
1) simple coatings allow more internal reflection and light scatter. They do NOT give a darker background. A better polish on the lens might, but if the better-polished lens is multi-coated it will yield an even darker background due to lesser amounts of scattered light. With high-end, expensive coatings, the RKE could transmit 98%+.
2) Ditto comment number 1 on planetary viewing. Reducing light scatter is the way to go to improve contrast on small details, not the other way around.
3) Light transmission and concentration of that light (see the spot diagrams for the design) are what is going to improve the brightness and contrast on DSOs, along with good polish on the lenses, strict adherence to the design parameters, and the long laundry list of other factors that improve what we call "contrast".
4) Seeing colors in stars is a matter of improving transmission through the eyepiece. Flattening the curve of the spectrum of transmission may or may not improve the visibility of colors in stars. Accenting the colors at the spectral position of peak sensitivity of the color-seeing cones in the eye might, though. Ironically, a non-flat spectrum might enhance colors more than a flat spectrum.

So your assertion is simply perpetuation of a myth from a company that chooses not to apply multi-coatings to their eyepieces. There is no basis in fact in that assertion. If their eyepieces had broadband anti-reflection coatings applied that were the proper materials for the lens composition, their eyepieces would be better and likely produce better contrast and have less internal light scatter.

#18 Sarkikos

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Posted 08 March 2013 - 12:56 PM

Then you are saying that what Vernonscope has been telling us all these years about Brandon eyepieces is all a myth? :grin:

Mike

#19 Sarkikos

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Posted 08 March 2013 - 01:08 PM

Don,

Though multi-coatings can, indeed, produce a different spectrum of transmission than simple magnesium fluoride coatings, the different spectrum is usually a HIGHER brightness/transmission at all visible wavelengths.


Yes, that is exactly why I'm trending toward all FMC for my deep-sky eyepieces. I want the highest transimission that I can get for seeing the faint fuzzies.

Mike

#20 Sarkikos

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Posted 08 March 2013 - 01:16 PM

Don,

2) Ditto comment number 1 on planetary viewing. Reducing light scatter is the way to go to improve contrast on small details, not the other way around.


Yes, I agree. And there is more than one way to reduce light scatter than fully multi-coating the lenses. Improvements in baffling, lens polish, lens design, types of glass, and the specific coatings used on different elements are other ways.

It is interesting that neither the Brandons nor XO's are FMC. Brandons are FC and XO's are MC. Is this simpler coating intended to reduce the low angle scatter that Vernonscope talks about? I doubt that simpler coatings are used in order to increase light scatter.

But this is for planet/lunar observation. Personally, I think FMC is the way to go for deep sky.

Mike

#21 Sarkikos

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Posted 08 March 2013 - 01:25 PM

Don,

3) Light transmission and concentration of that light (see the spot diagrams for the design) are what is going to improve the brightness and contrast on DSOs, along with good polish on the lenses, strict adherence to the design parameters, and the long laundry list of other factors that improve what we call "contrast".


Perhaps counterintuitively, reducing light transmission can also increase "contrast." Isn't this why some planet observers use ND filters for bright planets and the Moon, besides reducing the perceived brighntness? I don't use ND filters for planets, but the theory is at least that reducing the overall brightness will enhance the perceived contrast. The same sort of function may be taking place in simpler coatings for observers of DSO. Some observers have said that eyepieces with simpler coatings - such as Brandons, RKE and Sirius Plossls - bring out structure in bright nebulae and bright galaxies, making them appear more "contrasty."

Mike

#22 Sarkikos

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Posted 08 March 2013 - 01:37 PM

Don,

4) Seeing colors in stars is a matter of improving transmission through the eyepiece. Flattening the curve of the spectrum of transmission may or may not improve the visibility of colors in stars. Accenting the colors at the spectral position of peak sensitivity of the color-seeing cones in the eye might, though. Ironically, a non-flat spectrum might enhance colors more than a flat spectrum.


I have noticed that sometimes the color in stars seems more saturated if I defocus the star image a little. I've done this often for newbies so they can see the colors easier. Maybe something similar is happening for eyepieces with simpler coatings to make the stars seem more colorful. Of course, I don't mean that the stars are not as sharp, but that they are in some way more colorful. I know that many Brandon and RKE enthusiasts have said that stars seem more colorful and striking when viewed through these eyepieces.

Mike

#23 Starman1

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Posted 08 March 2013 - 04:39 PM

Activating the cones in the eye requires intensity of image. Larger apertures will bring out colors as will superior light transmission in a scope, higher Strehl ratio, more transparent atmosphere, superior polish on the lenses in the eyepiece, stronger contrast with the background, and so forth.

If people comment about that with Brandons or RKEs, it is likely because the eyepiece lenses may have superior polish, or higher transmissions, or cleaner eyepieces or simply what I like to refer to as the "it's new" phenomenon.

When I was in the bicycle business, and learned about frame design (and actually designed some), I learned about what makes a particular bicycle handle one way or the other and how to design in the handling characteristics I preferred. I noticed that people test-riding bikes didn't always prefer the design with the best handling, and I investigated why. In talking with a lot of sales people, I discovered that people invariably attributed better handling characteristics to whatever was newer, i.e. that the newest tires put on their bikes handled better, that the newer frame had superior handling, that the newer crankset performed better. And the reason was because it was different than what they had before. Difference was equated with Better.

I think the same thing occurs with eyepieces. People read a lot of praise for a specific brand or model, they buy one of them, and they discover for themselves that "the reviews were right". It's a case of "it's new, and different than what I had before, so it's obviously better", whether that's true or not. Six months later, the honeymoon is over, the product is just what it is and it may not be better, so it goes on sale or gets replaced with something different and, different is better.

Now obviously this isn't always true. Some people actually evaluate the eyepiece without any judgment-clouding preconceptions. But I'm not sure it is the majority of comments or reviews. In my experience, small number of lens eyepieces don't correct very well at the edge of the field, so typically, only the center is very sharp. Is that the characteristic of a planetary eyepiece? Or is having a larger number of lenses and a well-corrected, anastigmatic, outer field more desirable? Obviously light loss isn't an issue with planets, so one would think superior correction over the field would matter more than lens count.

When I added a Paracorr, it obviously added additional lenses and lost a little light. Yet, in Paracorr/no Paracorr tests, it was obvious I was seeing fainter stars with the Paracorr. Tightness of focus and concentration of the light into smaller spots was obviously the reason, yet what I saw was counter-intuitive. My very best view of Jupiter, ever, was through a stack containing 18 lenses (PowerMate, Paracorr, 8mm Ethos). And better, that great image held across at least 90% of the field as I watched the planet drift. With more color than I'd ever seen (bluish tones on the limb darkening, gray-green projections, ocher-colored EQ bands, salmon colored GRS, gray-green polar shading, beige, yellow, ivory, and cream colors in the bright bands, and pure white in some storms). Was it the stack of lenses, or simply magnificent seeing conditions? I credit the latter. And, perhaps, really well-polished optics.

It also points out that some eyepieces with poor correction everywhere except in the center aren't really good eyepieces overall, and that doesn't seem to relate to lens count in the eyepieces, except maybe inversely (witness the number of people praising the Delos as a "planetary" eyepiece). :grin:

By the way, your technique of slightly defocusing a star to see color more easily is often used by photographers, where in a tightly focused, long-duration shot is stacked with a much shorter one that is slightly defocused. This makes the colored stars appear more strongly colored.
Here is an example: Orion

#24 Sarkikos

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Posted 08 March 2013 - 06:03 PM

Don,

I think the same thing occurs with eyepieces. People read a lot of praise for a specific brand or model, they buy one of them, and they discover for themselves that "the reviews were right". It's a case of "it's new, and different than what I had before, so it's obviously better", whether that's true or not. Six months later, the honeymoon is over, the product is just what it is and it may not be better, so it goes on sale or gets replaced with something different and, different is better.

Now obviously this isn't always true. Some people actually evaluate the eyepiece without any judgment-clouding preconceptions. But I'm not sure it is the majority of comments or reviews.


Good reviews might influence me to try or even buy an eyepiece, but they won't make me keep one. I'm no fanboy. I don't have brand loyalty or product nostalgia, and I try not to succumb to argument from authority. If an eyepiece doesn't perform well for me in my telescopes, out it goes ... eventually. I do like to give it a fighting chance.

Mike

#25 Brett Carlson

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Posted 08 March 2013 - 09:21 PM

Interesting thread....I have two RKE's that I bought with a pair of scopes I bought together. One is a 28mm and a 21.5mm. I'm thinking that one or the other came with the Astroscan. Does anyone know what eyepieces came with the Astroscan?






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