Nagler's DeLite eyepieces

Saw them today in an indoor setting. Decent eyepieces, reminded me a bit of Radians. But according to Nagler, Radians were discontinued due to lack of glass (at a reasonable price) containing some rare-earth that was incorporated into the design. Correction seems good to the edge in a TV-85.

http://www.pbase.com/andersonrm/image/160569423

http://www.pbase.com/andersonrm/image/160569427

On Saturday, June 27, 2015 at 6:45:29 PM UTC-6, RichA wrote:
But according to Nagler, Radians were discontinued due to lack of glass (at a
reasonable price) containing some rare-earth that was incorporated into the
design.

I'm aware that Lanthanum is used in certain premium optical glasses.

And I know about the controversy where China decided it wanted to keep its rare
earths for its own industry.

But China's actions would normally cause only a *temporary* disruption - it
does not have a monopoly, or anything even close, on the minerals from which
rare earths are mined. Those minerals are commonplace. In most places, they're
only refined up to the point of making "mischmetal", which is used for making
flints for lighters.

What China has exclusively is the plants that carry out the difficult process
of refining the individual rare earths - they're so similar chemically that
it's almost as bad as separating isotopes.

Nothing's stopping other countries from making them, except:

a) the investment, if made by a *private* concern, rather than the government,
being wasted money once China decides to relent, and

b) environmental objections in other countries to the setting up of such plants.

And bad memories of World War II might complicate matters if, say, the Japanese
Government decided to fund the construction of a rare earth refining plant in
Indonesia.

John Savard

On Sunday, 28 June 2015 10:40:56 UTC-4, Quadibloc wrote:
On Saturday, June 27, 2015 at 6:45:29 PM UTC-6, RichA wrote:
But according to Nagler, Radians were discontinued due to lack of glass (at a
reasonable price) containing some rare-earth that was incorporated into the
design.

I'm aware that Lanthanum is used in certain premium optical glasses.

And I know about the controversy where China decided it wanted to keep its rare
earths for its own industry.

But China's actions would normally cause only a *temporary* disruption - it
does not have a monopoly, or anything even close, on the minerals from which
rare earths are mined. Those minerals are commonplace. In most places, they're
only refined up to the point of making "mischmetal", which is used for making
flints for lighters.

What China has exclusively is the plants that carry out the difficult process
of refining the individual rare earths - they're so similar chemically that
it's almost as bad as separating isotopes.

Nothing's stopping other countries from making them, except:

a) the investment, if made by a *private* concern, rather than the government,
being wasted money once China decides to relent, and

b) environmental objections in other countries to the setting up of such plants.

And bad memories of World War II might complicate matters if, say, the Japanese
Government decided to fund the construction of a rare earth refining plant in
Indonesia.

John Savard

They control enough of the rare earth stocks so that Americans were actually considering "de-mothballing" mines closed in the 50's that contained them.. People crowed about gold prices jumping 300% but some rare-earths went up 10x in the same period. However, enviroKOOKS will scream bloody murder if they try to restart that mining industry stateside.

Well corrected eyepieces do not need to use particularly exotic glass. The main question is whether it's economical to make them.

http://www.richardfisher.com

On Monday, 29 June 2015 15:27:44 UTC-4, Helpful person wrote:
Well corrected eyepieces do not need to use particularly exotic glass. The main question is whether it's economical to make them.

http://www.richardfisher.com

ALL highly-corrected eyepieces use exotic glass.

On Monday, June 29, 2015 at 8:30:16 PM UTC-7, RichA wrote:
On Monday, 29 June 2015 15:27:44 UTC-4, Helpful person wrote:
Well corrected eyepieces do not need to use particularly exotic glass. The main question is whether it's economical to make them.

http://www.richardfisher.com

ALL highly-corrected eyepieces use exotic glass.

You are lecturing an optical engineer?

On Monday, 29 June 2015 23:37:37 UTC-4, palsing wrote:
On Monday, June 29, 2015 at 8:30:16 PM UTC-7, RichA wrote:
On Monday, 29 June 2015 15:27:44 UTC-4, Helpful person wrote:
Well corrected eyepieces do not need to use particularly exotic glass. The main question is whether it's economical to make them.

http://www.richardfisher.com

ALL highly-corrected eyepieces use exotic glass.

You are lecturing an optical engineer?

Tell me of ones that don't then.

On Tuesday, June 30, 2015 at 12:52:33 AM UTC-6, RichA wrote:
On Monday, 29 June 2015 23:37:37 UTC-4, palsing wrote:
On Monday, June 29, 2015 at 8:30:16 PM UTC-7, RichA wrote:

ALL highly-corrected eyepieces use exotic glass.

You are lecturing an optical engineer?

Tell me of ones that don't then.

In principle, exotic glasses aren't needed in order to make a highly-corrected
lens.

It is true, though, that the oldest and simplest glasses, if used exclusively,
do prevent some aberrations from being corrected: hence, the Petzval portrait
lens, which used astigmatism to compensate for an uncorrectable curvature of
field by flattening at least one image plane.

However, the "new" glasses which solved that problem can hardly be termed
'exotic' by today's standards.

What exotic glasses let you do is make a well-corrected lens lighter and
smaller. And they let you do more ambitious things. So while the original
Nagler did not use any exotic glasses, it did have the 'kidney-bean' problem,
and the ones with wider fields do all use exotic glasses.

John Savard

On Tuesday, June 30, 2015 at 4:15:31 AM UTC-4, Quadibloc wrote:

In principle, exotic glasses aren't needed in order to make a highly-corrected
lens.

It is true, though, that the oldest and simplest glasses, if used exclusively,
do prevent some aberrations from being corrected: hence, the Petzval portrait
lens, which used astigmatism to compensate for an uncorrectable curvature of
field by flattening at least one image plane.

However, the "new" glasses which solved that problem can hardly be termed
'exotic' by today's standards.

What exotic glasses let you do is make a well-corrected lens lighter and
smaller. And they let you do more ambitious things. So while the original
Nagler did not use any exotic glasses, it did have the 'kidney-bean' problem,
and the ones with wider fields do all use exotic glasses.

John Savard

Correct. However, there are some techniques that have not been used which obtain good performance without expensive glass or extra elements. Sorry, can't discuss but I'm sure I'm not the only one to have experimented with eyepiece design.

http://www.richardfisher.com

On Tuesday, 30 June 2015 04:15:31 UTC-4, Quadibloc wrote:
On Tuesday, June 30, 2015 at 12:52:33 AM UTC-6, RichA wrote:
On Monday, 29 June 2015 23:37:37 UTC-4, palsing wrote:
On Monday, June 29, 2015 at 8:30:16 PM UTC-7, RichA wrote:

ALL highly-corrected eyepieces use exotic glass.

You are lecturing an optical engineer?

Tell me of ones that don't then.

In principle, exotic glasses aren't needed in order to make a highly-corrected
lens.

It is true, though, that the oldest and simplest glasses, if used exclusively,
do prevent some aberrations from being corrected: hence, the Petzval portrait
lens, which used astigmatism to compensate for an uncorrectable curvature of
field by flattening at least one image plane.

However, the "new" glasses which solved that problem can hardly be termed
'exotic' by today's standards.

Keep splitting those hairs.