TheSkySearchers

I still have my circa 1979 Edmund Scientific RKE, a modified Kellner design which Edmund patented back in the 1970's. It came with my red tube 4.25" reflector known as the Super Space Conqueror. Since the scope was f/10 it was pretty forgiving on eyepieces and even Kellners worked fine. Anyone still have an original RKE?



I still use mine in my 6" achromat. I think there was a hiatus as Edmund's business waned but it was reborn as Edmund Optics and they are still selling the design. Just curious what others think of them? Not as well-known as the Astroscan was in the 1970's but still an important piece of eyepiece lore.

I don't have one. This is only because, having what I have, it's easy to ignore temptation to buy the set. I'd vote for classic. I've had a quick look through them on other's kit. When I'm in a good mood, the floating field effect gets me giggly. When I'm grumpy, it's too gimmicky.

I do like the RKE eyepieces, so classics for me and still use them.
Besides the 28mm with its party trick the line is actually quite good and the prices still reasonable.
Ordering them in EU can get expensive with duty and taxes though. (€ 102+20% DPH here)
The 15mm and 21,5mm are standouts but I do not think they are produced anymore.
For refractors the RKE barlow is much to long but is good for large (300mm+) newtonians

I still have the cheap 3x barlow that came with the Edmund scope, but it's relegated to the junk drawer. I don't list it in my signature. Hard for me to throw anything astronomical away.

I have a hard time getting rid of astro things as well until it becomes a issue
If I listed everything I would not have room to comment!

Is it a different barlow from the RKE 2.5x?
It is not my best barlow but it does work reasonably well.
These long barlows were designed for use with newtonian telescopes to have the light cone entering closer to the secondary.
It works well in my f/10 - f/15 refractors but I would not use it in anything shorter.

I meant the 2.5x in general I am not a barlow fan but it worked pretty well with the 4.25" I remember zeroing in on the Trapezium through it, Hey there are four stars!

Since you have the 28mm, you should look for a 15mm.
They are usually not very expensive used and was one of the best from the lineup.

Barlows for me are view dependant. When I do use them I actually like using odd incremental barlows.
1.6x, 1.8x, 2.4x etcetera. I have had a 2x TeleVue powermate for better than a decade now and I think I have used it maybe 3-4 times...
It does make a good but expensive paperweight though

I should get a 15mm as well!

Hopefully sometime this month I may be able to recommend a 20mm as well

I really need to pay attention when tired, the incoming 20mm is a Brandon not a RKE.

I cannibalized from other EPs so could have a nice weighty chromed brass barrel on my set. They perform great in my scopes and show star colors exceptionally well - always want to keep a single coat set around. No one has a same barrel type as used for the 28.7mm so I just buffed the anodized layer off. RKE = Rank, Kaspereit, Erfle per the Edmund patent submission FYI. The pre-RKE 28.7mm, usually marked as a 1-1/8", is an asymmetrical Plossl war surplus optic.

I love my RKE and have used then for quite a few years.

Lady Fraktor wrote: ↑Tue Jan 10, 2023 5:27 am I love my RKE and have used then for quite a few years.

I have bought and sold more than 300 different eyepieces over the years so have been through a lot. I had a full set of the RKEs that I added the chromed brass barrels to and after a few years sold them. Of all the eyepieces I have been through and let go of, that set was the only one I truly regretted selling. So some years later I reacquired the RKEs once more, and was lucky to be able to source a 15mm used as that focal length was already discontinued by Edmund. I have to say that will NEVER let go of my current set! I feel the same way about the Takahashi LEs. Both lines just have what I consider a unique gestalt about them that makes them special and enjoyable.

I have done a mass purge of eyepieces over the last year but the RKE remain. I only have a few Tak LE but enjoy the ones I do have.

WilliamPaolini wrote: ↑Tue Jan 10, 2023 6:20 pm

Lady Fraktor wrote: ↑Tue Jan 10, 2023 5:27 am I love my RKE and have used then for quite a few years.

I have bought and sold more than 300 different eyepieces over the years so have been through a lot. I had a full set of the RKEs that I added the chromed brass barrels to and after a few years sold them. Of all the eyepieces I have been through and let go of, that set was the only one I truly regretted selling. So some years later I reacquired the RKEs once more, and was lucky to be able to source a 15mm used as that focal length was already discontinued by Edmund. I have to say that will NEVER let go of my current set! I feel the same way about the Takahashi LEs. Both lines just have what I consider a unique gestalt about them that makes them special and enjoyable.

Good to hear. The 28mm always has been a nice performer.

helicon wrote: ↑Mon Jan 16, 2023 11:28 pm The 28mm always has been a nice performer.

So it is. I have mine some twelve years. Especially for the nice floating field effect. I use it mainly in my f/13 Mak. I used to have a 15mm too, but eventually sold it again as my 14mm Baader Morpheus outclassed it by far.

John Baars wrote: ↑Thu Jan 26, 2023 9:13 am

helicon wrote: ↑Mon Jan 16, 2023 11:28 pm The 28mm always has been a nice performer.

So it is. I have mine some twelve years. Especially for the nice floating field effect. I use it mainly in my f/13 Mak. I used to have a 15mm too, but eventually sold it again as my 14mm Baader Morpheus outclassed it by far.

They seem to have quite a lifespan!

helicon wrote: ↑Thu Jan 26, 2023 3:14 pm They seem to have quite a lifespan!

I think I have had my set for about 12-15 years as well.

On of the 28mm's I have, is the 1-1/8" version which is really an asymmetrical Plossl. I got that from the Edmund store with one of my first telescope's from there, a 4.25" Reflector way back in mid 60's! The showroom they used to have in Barrington, NJ was a wonderland of science stuff for adults and kids. Used to love going there. They also had a surplus room with all kinds of neat odds and ends which of course little kids just love dipping their hands into the bins and exploring those treasures. And they made the shop fun too. In the middle of the main store was an actual submarine periscope they mounted that popped out the roof of the building so you could look around. And the hallway between the main showroom and the surplus room had a bunch of those circus mirrors that distorted the view making you appear long and stretched or short and round. Just a wonderful wonderful place. Went there many times as a kid and later brought my kids there as well. So bummed when they closed it. It really was the place that got me interested in science. Online shopping cannot compare to a brick-and-mortar store where a kid can see up close and touch and feel all the unusual treasures!

Here's links to some old pics of the place...

https://www.cloudynights.com/uploads/mo ... 494975.jpg

https://cloudfront-us-east-1.images.arc ... D4P3K4.jpg

https://upload.wikimedia.org/wikipedia/ ... 0926034559

As far as the outdated question, here are my thoughts...

I personally do not consider them outdated as they perform perfectly fine. Of course their 45 degree AFOV makes them a bit of an oddity in today's market. I feel they are a bit over priced given their light aluminum barrels. If they had conventional chromed brass barrels like many of the classic designs can come with then their current $107 USD price might be easier to swallow - I think $75 might be better. However, they are also one of the few single coated eyepieces available, Brandons being another and some cheap things on ebay. I like having some single coats in the stall as they provide a bit of a different view from multicoats having exceptionally dark backgrounds and IMO showing subtle star colors better and producing cleaner star points many times which is why I like them for doubles. When I had my 10" f/4.7 Dob I used to use them often in that instrument as they bought in double stars very cleanly so were preferred for that task. Yes they are only a 3 element design so the off-axis will suffer but in my testing no worse than an Abbe in faster focal ratio scopes for the 21mm thru 8mm. The 8mm is easily on par for planetary with the TV 8mm Plossl as I did an exhausting personal compare of those two over two full years and could not determine a winner, so a dead heat. Their diminutive size makes them a pleasure to take into the field so no large suitcase needed to get the set out there. The oddity of the line is the 28mm as its eye relief is very long so difficult to keep the view. The length of its eye relief and width of its housing is such that when viewing the housing is right at the blind spot in the human eye so that in addition to its very slim housing makes the housing appear to vanish so only the AFOV is there seemingly almost floating in front of you. This eyepiece also does not handle faster focal ratios well so it's off-axis can be pretty distorted with faster focal ratios. In my f/8 Apos thought it is plenty good enough, although of the line I consider the 28mm more as a novelty eyepiece for its floaty view ranter than one I would grab for general viewing. However, I found the 28mm does have a special usage that I like, and that is to Barlow to extend the eye relief even more which allows me to sketch more easily as I can stand far off from the eyepiece so I can simply move my eyes from the direction of the eyepiece to the sketch pad without dipping near the eyepiece so makes sketching much easier as like liking at something with the naked eye. So I keep a pair of those for the binoviewer as well.

The feeling of the frame disappearing to a thin line around the image also occurs with the 9mm Morpheus, 35mm Ultrascopic, and 3-6mm Nagler Zoom as I have noticed.
The thin black "line around the field" is a bit broader than in the 28.7mm RKE (how Edmund used to label it), but each exemplifies how, when the eye relief is just the right length,
the outer barrel thins down to just a thin black line by perspective.
You do have to be able to float above the eyepiece in just the right spot, and it is easier to see without glasses.