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A "Practical" Planetary Eyepiece?

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129 replies to this topic

#126 Starman1

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Posted 09 June 2020 - 10:34 AM

My memories of the Königs I owned in the '80s were that they were extremely sharp in the middle 50% of the field in my f/6.5 and f/5 instruments of the time.

That they weren't as sharp at the edge, I know now, wasn't so much a fault of the eyepiece as my using them in f/ratios below where they are appropriately used.

I wish I'd owned them when I still had my f/15 refractor.

My longest scope now, though, is f/7, so they are eyepieces from my past.


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#127 MartinPond

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Posted 09 June 2020 - 05:37 PM

Definitely 1,2,1s.

For me and planetary, 1,2 is the ticket.

Happy almost to F5.  (and just 53 degrees, though)



#128 luxo II

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Posted 09 June 2020 - 07:27 PM

Thomas in the 1980's the only Konigs in my country were UO... zeiss or other high-end ones were simply not available. And they were indeed distinctly inferior to other types I had.

 

Don't forget this was pre-internet and the only way people knew what was available was from ads in magazines - especially S&T, or at star parties.


Edited by luxo II, 09 June 2020 - 07:30 PM.


#129 j.gardavsky

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Posted 10 June 2020 - 05:26 AM

My memories of the Königs I owned in the '80s were that they were extremely sharp in the middle 50% of the field in my f/6.5 and f/5 instruments of the time.

That they weren't as sharp at the edge, I know now, wasn't so much a fault of the eyepiece as my using them in f/ratios below where they are appropriately used.

I wish I'd owned them when I still had my f/15 refractor.

My longest scope now, though, is f/7, so they are eyepieces from my past.

Flattening the field of the Königs may require one aspheric surface, even if the special glass materials (Sonderglas) are used.

Then, they can be made orthoscopic, and they allow to mount a measurement graticule (reticle), as indicated with capital M (Messokular) on the inscription.

 

In the version with a field flattener lens, the internal focusing mechanics will be added as a "complication".

For me, the main advantage of the internal focusing is the possibility to compensate the last mismatch in the planarity between the image giving optics (telescope, microscope) and the visual perception at the eye relief of the eyepiece.

 

So, you finally get a flat, sharp edge-to-edge, and orthoscopic field, on a wide range of image giving optical systems,

 

JG


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#130 Thomas_M44

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Posted 10 June 2020 - 02:14 PM

What EP's I've chosen for planetary viewing with my f/7 TV-85 apo:

 

I bought a full set of TV Plossls (except the 41mm) because of the versatility for general observation, plus pretty good for planetary with nice color rendition and contrast.  I feel the TV Plossl design approach is an intelligent compromise for general-use.  Granted, the adjustments to accommodate scopes as fast as f/4 do compromise these EP's a bit, but I do understand and respect that design decision.

 

I also obtained all of the current KK Fujiyama ortho's from 25 to 6mm.  My thinking was that the KK ortho's would give a bit of an edge in sharpness and overall clarity for certain types of lunar and planetary viewing as compared to the TV Plossls, though at the expense of perhaps having somewhat inferior contrast and color rendition as compared to the TV Plossls.

 

I avoided going any shorter in EP FL than 6mm due to eye relief considerations, and rather decided to get a bunch of high quality barlows, a few TV Powermates,  plus some extension tubes.

 

I have the 2.5X and 5X Powermates for use with the TV Plossl's to avoid vignetting, particularly with the longer FL EP's.

 

I also obtained a Nikon EiC-16 1.6X barlow plus 1" Blue Fireball extension tube as per russell23's wise suggestions. I also have  the TV 2X and 3X barlows at ready.  So this gives me tons of magnification options with the KK ortho's.

 

Since my scope presently has an alt/az mounting only,  I decided against obtaining more exotic high-magnification planetary EP's with FOV's under 40-deg such as monocentrics.  When I obtain a driven mounting, then maybe I'll also grab a couple monocentrics or ball lens types to try just for curiosity.

 

I do totally understand Bill_P's idea, however, and I like it.  Personally, I don't plan to go faster than f/7 with any future telescope purchases, and so it would be nice if there were more highly-tuned affordable  EP's for moderate/middle focal-ratio scopes.

 

For the time being, I'm very happy settling with the TV Plossl's and KK ortho's for my planetary and lunar needs.  I know there are higher performing planetary EP's out there, but I really don't feel like I'm giving up that much with my basic Plossl's and ortho's.


Edited by Thomas_M44, 10 June 2020 - 03:03 PM.

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