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Triple Deuce Coupe: OOPL (opened-out plossl)

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#1 MartinPond

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Posted 24 November 2017 - 10:52 AM

Another cool design found (or did someone do this before?)

I have seen my own 2,2,2 (same fls, precision 45-deg) and the Kaspereit,

  but this "Triple Deuce Coupe" is a whole 'nother kettle of fish...

 

DSCF0525.JPG

 

 

I was tinkering with cleaning up the edges of  my recent

   thick-doublet-plossl theme, with a tight top set and a doublet

   field lens below.  The field correction and the field width 

   both blew up past my expectations.   The flexibility of the

   Konig 1//2 core was known, but this seems to point into

   another way of leveraging the Plossl core (other than the Erfle family).

 

 


Edited by MartinPond, 24 November 2017 - 03:19 PM.

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#2 Scott in NC

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Posted 24 November 2017 - 10:54 AM

Cool! Thanks for sharing that.  Now you just need to patent that as the MartinPond eyepiece.  Quick, before the Chinese clones come out! :grin:


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#3 MartinPond

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Posted 24 November 2017 - 11:06 AM

Cool! Thanks for sharing that.  Now you just need to patent that as the MartinPond eyepiece.  Quick, before the Chinese clones come out! grin.gif

More fun from down on the Pond!

 

This is a non-patent public disclosure, actually.

Once it's out of the bag....no monopoly.

 

EP makers are free to use it (and tweek it, make it nice?), but they can't patent it either,

if their variant is an obvious extension of this.

It is now "common knowledge" in a key forum.

I'd love a nicely machined commercial version, especially a TV-style 

internal-flat-black-threaded chamber right there in the middle....

 

Maybe makers could carry on the ID with the anti-TM "Triple Deuce Coupe"..

 

I think a manufacturer's first challenge would be to assure the 'thick doublets'.

A perfectly-placed field stop (~65 degrees) would be nice,

then re-jigger the parameters for all-barrel imperviousness.

 

I couldn't bring myself to blacken the outsides.  The contrast is great,

and the layer-cake looks so awesome with some clear layers.

 

There are a few big-scope experimenters playing with the "DiPlossl" in 2-inch.

That's a smaller afov but extreme precision.

 

There are other EPs that do this, basically.

This one is distinguished by no winking or blackouts.

As you approach the field gets bigger, as you move left or right

the view simply slips by...no jinking or blinking.

As an mfg product, all plain doublets is probably more affordable than 

a number of cupped or meniscus singles..


Edited by MartinPond, 24 November 2017 - 03:18 PM.

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#4 Bob4BVM

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Posted 25 November 2017 - 01:08 AM

Martin you continue to amaze me !

Are we gonna stack this one from the bottom ?  Sent you a PM

Bob



#5 MartinPond

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Posted 25 November 2017 - 11:33 PM

Will need to round up more traceable parts first...

that work the same...

 

Then, time to think about keeping it simple.

Machining for this one would be more complex than 

the DiPlossl housings you made (nice job!)...

 

 

It may work well...

the field lens role is not as exacting,

so std. pocket-bin objectives will be tried .

 

Having a 3D printer for spacer rings would be great...

to speed iterations.  (later you try to incoporate into the body)..

 

But....first, must rummage up a traceable set..



#6 luxo II

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Posted 28 November 2017 - 06:29 PM

Ha. I made one of these 30 year ago while experimenting with surplus doublets. Was quite nice and I eventually gave it away with a scope I sold.

I’m sure many others have tried this too, it’s an obvious extension of the Plossl and works surprisingly well.

Far from being a new idea !

Edited by luxo II, 28 November 2017 - 06:31 PM.


#7 MartinPond

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Posted 29 November 2017 - 09:06 AM

Most things are 'obvious extensions'....to a tinkerer.

Since you are the first other to mention it, it's not really "Far from being a new idea"..

(in that there really aren't "many others" who horse around)...

Technical hobbies used to be more hands-on and less 'salon/purchase'...so

   I'm just having fun being a throwback, like radio buffs who tweek their own

   shortwave things.

I haven't seen this design commercially.   I need to tune out the edges a bit more

to have a throw-down against some popular middle commercial EPs.

It certainly has the Expanse beat for easy eye approach, for me, and the contrast is excellent.

 

 

The big difference, in my case, is the thicker doublets from the Japanese

   binoc EPs.   They will produce a plossl with a clean 60 degrees in a long barrel.

It's too bad the 'thick long barrel plossl' isn't available commercially.   "Long" starts at

a mere F7 equivalent for many EPs.  I suppose Abbe/Ortho users know the boon of

long-equivalent  usage..

Anyway...these doublets are not your typical surplus stock.

This scheme is icing on that cake, and opens to 70deg...

 

I know you can't do that with standard doublets.

Then again.....your surplus doublets could have been thick at the time....

And..maybe you aren't ordinary or obvious yourself ;-)

.

Weaker doublet stacks can be surprisingly flexible.

 

4 with about the same value, touching, make a super-correct DiPlossl.

Only 50 degrees, but super with short or long barrels.

A 2,2,2 same-fl-stack can be even better with a short barrel.

 

There are the 3 in the Kaspereit, but in that case the middle doublet gets in the way

 physically/optically when trying for afov, so the singlet of the Erfle is a better play.

 

I've been trying for a tapered stack, a 2,2,2,2, but tht idea is very sensitive to the parameters.

Having a strong top pair and a weak field lens seems more tolerant and flexible.


Edited by MartinPond, 29 November 2017 - 09:21 AM.


#8 luxo II

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Posted 29 November 2017 - 05:08 PM

Martin, at the time I had collected a pile of assorted optical components which were leftovers presumably from a binocular manufacturer here. Like yours the smaller doublets were quite thick but the coatings were just ordinary MgF, common at that time.

What inspired me was that by chance I realised the doublets fitted neatly inside some plastic tube which was also amenable to being cobbled into a workable eyepiece barrel.

From memory they also made a fair 2,2,2 arrangement with a bi-convex doublet inserted in the middle.

#9 MartinPond

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Posted 29 November 2017 - 08:34 PM

Aha....though I think people  who dabble are even more rare now than then!

 

Either 2,2,2 or 2,2,2,2   are surprisingly flexible...

 

Sounds like you did a sort of Erfle-like or KAspereit-like 2,2,2 .. .. extra field width.

I have  a gap in FL values,   but a singlet in the midle makes a nice "Erfle-lite"..

 

If you had some Russian binocs for sources....those can have many elements!  And so...to play with.

 

For all-same or mostly-same FLs,  I liked the DiPlossl (2,2,2,2 ...all domes toward middle) a lot, at 50-deg.

The 2,2,2, with 21mm objectives, is 45 degrees but fantastic.....I go all-domes-up, French-style, for 

  extreme scattering rejection....beats the orthos. However, I can only go to ~30mm FL....

 

The tight-strong top group with a wide field lens has allowed me to break out into wider fields.

Some of the field success is likely due to the coincidental vaues I have to work with.

"Out of limitations, new forms emerge" --Georges Braque

 

I'm dropping my layer-cake or "Sloika" design...it looks elegant but it is way too demanding for FL values

   and all the benefits fade out with length.. 

 

I think many things still echo the limitations that led to Konigs basic forms.   Economy was really important then.

Even simple optics were extremely expensive.  It's good to revisit designs.  I like the availability of really good

doublets and I like trading off for better contrast and no blackouts.  This could be a leading design for me,

but I have to optimize and have a showdown with some commercial ones.  The ortho-triple 2,2,2-same type I am all

set with...for life....but I can't make one easily below 25mm...it's the parts.




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