86 replies to this topic

[izar187]

The Edmund  RKE is an unusually underrated and misunderstood eyepiece.

 

The current ones have very nice Japanese-made lens sets, and the optical quality is excellent.

 

The absolute best views I obtained of Mars with my TV85 this last conjunction were using the 21mm RKE plus 5X TV Powermate. The sharpness and definition bested my KK orthos and TeleVue Plossls by a useful margin.

 

Saw that the 21 is now in a "contact us" status on their web page.

Perhaps Edmund will be able to bring back the whole set at some point, for folks who would like them.

For astronomy, seems like the future market will be small.

Perhaps along with industrial and medical applications, altogether will push up demand enough for more production.

 

21mm + 5x Powermate: that is not that surprising an outcome.

Two sharp and transparent components. 

Equaling one seven element 4mm focal length, long comfy eye relief, small/no astigmatism, zero coma afflicted in this application.

That Powermate would be presenting the RKE with a likely perfect focal ratio to work with.

A match made for the heavens for the 21. 

[Mike McShan]

I contacted Edmund about the 21mm last week, and they said that they will be available again in late January. 

 

fyi, Mike 

[AdmiralAckbar]

I recommend a 4x telenegative barlow (i.e., Siebert) instead of the 5x Powermate, mainly because, used with the 8mm, it increases the eye relief, providing the equivalent of a comfortable 2mm eyepiece. I find 2mm a useful focal length when observing doubles.

 

With a 5x Powermate, the 8mm becomes 1.6mm, and without added eye relief. I don't find that useful.

 

Granted, with a 4x barlow, the eye relief of the 28mm (now functioning as 7mm) is quite long. But I use this combo a lot and do not find the long ER to be a hindrance at all. In fact, I much prefer this "7mm" combo to the 8mm RKE, which I only like to use barlowed since the eyepiece lacks eye relief.

Edited by AdmiralAckbar, 12 December 2021 - 01:20 PM.

[luxo II]

I don't find that useful.

All depends on your scope. On mine, 2mm gives 1600X which is a wee bit too much. 6-7mm is nice for doubles.

Edited by luxo II, 12 December 2021 - 07:46 PM.

[Thomas_M44]

I recommend a 4x telenegative barlow (i.e., Siebert) instead of the 5x Powermate, mainly because, used with the 8mm, it increases the eye relief, providing the equivalent of a comfortable 2mm eyepiece. I find 2mm a useful focal length when observing doubles.

 

With a 5x Powermate, the 8mm becomes 1.6mm, and without added eye relief. I don't find that useful.

 

Granted, with a 4x barlow, the eye relief of the 28mm (now functioning as 7mm) is quite long. But I use this combo a lot and do not find the long ER to be a hindrance at all. In fact, I much prefer this "7mm" combo to the 8mm RKE, which I only like to use barlowed since the eyepiece lacks eye relief.

The TeleVue 3X Barlow makes just under 4X when a 1.5” extension tube is placed between the Barlow and eyepiece, and so this is also a very good option for use with the 15mm, 12mm and 8mm RKE’s.

 

I take a different approach to use of my RKE’s for planetary magnification: I Generally don’t use my 12mm or 8mm RKE’s very often due to the limited eye-relief, but rather use the 5X Powermate ( with or without extension tubes to increase magnification to 5.75X or 6X) with my 21mm or 28mm RKE’s.

 

I’d also use a 15mm RKE sometime if I had one, but Edmund has completely discontinued making the 15mm unfortunately.

 

 

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Edited by Thomas_M44, 12 December 2021 - 07:58 PM.

[AdmiralAckbar]

All depends on your scope. On mine, 2mm gives 1600X which is a wee bit too much. 6-7mm is nice for doubles.

That's not the point. My point was that I find an eyepiece focal length of 2mm with added eye relief more useful than 1.6mm without added eye relief. In your case, neither would be helpful. So, why argue a point that doesn't apply to you...?

Edited by AdmiralAckbar, 13 December 2021 - 12:21 AM.

[Observer1980]

That's not the point. My point was that I find an eyepiece focal length of 2mm more useful than 1.6mm. In your case, neither would be helpful. So, why argue a point that doesn't apply to you...?

ITS A TRAP!!!!

[luxo II]

OP was discussing an 8" dob... probably around f/5. The RKE's were originally intended for the Astroscan, and are quite a suitable match for that.

 

At the time I had an RKE set I had a 6" f/5, 6" f/8, 6" f/19 and an 8" f/7 and the RKE's were fine with all of these scopes.

 

2mm is not a credible focal length for this, IMHO.

Edited by luxo II, 13 December 2021 - 01:25 AM.

[AdmiralAckbar]

OP was discussing an 8" dob... probably around f/5. The RKE's were originally intended for the Astroscan, and are quite a suitable match for that.

 

At the time I had an RKE set I had a 6" f/5, 6" f/8, 6" f/19 and an 8" f/7 and the RKE's were fine with all of these scopes.

 

2mm is not a credible focal length for this, IMHO.

I was not making the claim that 2mm is a universally useful focal length. That seems to be the claim that you're arguing against. I agree that that would be a problematic claim... which is why I didn't make it. The claim that I made was: I find 2mm with additional eye relief more helpful than 1.6mm without additional eye relief.

_________________________________

 

On another note: I used a pair of the 28mm RKEs last night in my (new to me) Oberwerk BT100XLED binocular telescope. Off-axis astigmatism? Yes. Somewhat finnicky eye placement? Yes. Did I care? No! It was truly like looking on a floating slice of the cosmos... like sitting on a platform somewhere in space, beholding everything with my naked eyes. What a cool eyepiece.

Edited by AdmiralAckbar, 22 December 2021 - 12:09 PM.

[REC]

I had a 32mm Brandon once and it was the type with no eye cup and it was only about 1.25" long. Huge eye relief. When just concentrating on the object, the barrel just got lost in the dark. I dropped it a couple time on my patio and bent the barrell so bad it could not be repaired. The company replaced it with a newer longer version and the floating effect was gone!

 

I recently looked through a 28mm RKE in one of the clubs telescope at Jupiter and it was fun.

[MarkGregory]

Your post made me laugh. It is true, the 28mm RKE oculars have a stellar reputation and following. So much so that I went out and bought a set for Bino viewing. My analysis after using them.  No big deal. Not as great as what I expected. Nice, but not great. Now, let’s see how many people call me crazy. Lol 

I couldn’t figure out how to edit my  post so I simply added a comment.  I want to revise my ealier comment. I said these were “no big deal.” After using them several more times I now better understand the moon walk aspect of these oculars. Really are very nice and different from other eyepieces. They do seem to be a big deal. Five thumbs up. 

[Neptune]

This reminds me of my first view through my buddies 28mm RKE back in 1978 using my C-8. To date, I had only used my 40mm & 25mm Kellner's, University Optics Ortho's and my venerable 20mm Meade wide field.  The 28mm to this day was very memorable. It could be because of my limited experience at the eyepiece, but the view in that eyepiece was different, almost 3-D like. I have since seen this type of view in a borrowed 48mm Brandon.