Soap Bubble lenses, and Mercury Mirrors?

I understand the largest practical lens size is around 40" with glass. well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

Do you just want to look at your zenith?

--
Jamie
-------
"Kris T" wrote in message
...
I understand the largest practical lens size is around 40" with glass.
well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

Do you just want to look at your zenith?

--
Jamie
-------
"Kris T" wrote in message
...
I understand the largest practical lens size is around 40" with glass.
well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

On Mon, 16 Feb 2004 20:34:03 -0700, Kris T wrote:

I understand the largest practical lens size is around 40" with glass. well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

It would have to hold its shape to a fraction of a wavelength, and the bubble
would need to be filled with something having an index of refraction quite
different from air. I can't think of anything even close to meeting these
requirements. Plus, there is really no reason to do this when mirrors work
better than lenses, anyway.

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

It's been done. You can produce a rather acceptable large mirror this way, but
it is limited to imaging the zenith. Not too practical for most uses.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Mon, 16 Feb 2004 20:34:03 -0700, Kris T wrote:

I understand the largest practical lens size is around 40" with glass. well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

It would have to hold its shape to a fraction of a wavelength, and the bubble
would need to be filled with something having an index of refraction quite
different from air. I can't think of anything even close to meeting these
requirements. Plus, there is really no reason to do this when mirrors work
better than lenses, anyway.

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

It's been done. You can produce a rather acceptable large mirror this way, but
it is limited to imaging the zenith. Not too practical for most uses.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Kris T wrote in
:

I understand the largest practical lens size is around 40" with glass.
well what about some sort of self sustaining liquid lens, sort of a
soap bubble lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the
liquid wouldn't need to be deep.

I think spinning Mercury has been done. Only good for the Zenith though.
Was the soap bubble idea a joke?

L.

Kris T wrote in
:

I understand the largest practical lens size is around 40" with glass.
well what about some sort of self sustaining liquid lens, sort of a
soap bubble lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the
liquid wouldn't need to be deep.

I think spinning Mercury has been done. Only good for the Zenith though.
Was the soap bubble idea a joke?

L.

both have been tried many times. when it comes to liquids - think about it!
They arent stable media. Hardened bubbles blown from various substances
another matter, but still they lack the critical internal and surface
accuracies to
meet most optical reaquirements - some optical windows for aerocraft were
formed this way.

experiments were done in space (zero gravity) spinning several liquid metals
but again maintaining surface accuracy over time a problem. any medium which
has motion is usually not a good optical component. spinning certain metals
which
then harden offer some possibilities especially if they can be quick polished
and
put into service quickly but metals which are conducive to such a process also
turn out to have relatively soft surfaces and dont take a hard smooth
predictably
uniform surface (free of zones or flaws). epoxies have been tried. ceramics
have
been tested. experiments continue and sooner or later amateur telescopes will
have free molded ceramic (epoxy?) mirrors. Its almost inevitable withtime.
Jerry





Kris T wrote:

I understand the largest practical lens size is around 40" with glass. well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

both have been tried many times. when it comes to liquids - think about it!
They arent stable media. Hardened bubbles blown from various substances
another matter, but still they lack the critical internal and surface
accuracies to
meet most optical reaquirements - some optical windows for aerocraft were
formed this way.

experiments were done in space (zero gravity) spinning several liquid metals
but again maintaining surface accuracy over time a problem. any medium which
has motion is usually not a good optical component. spinning certain metals
which
then harden offer some possibilities especially if they can be quick polished
and
put into service quickly but metals which are conducive to such a process also
turn out to have relatively soft surfaces and dont take a hard smooth
predictably
uniform surface (free of zones or flaws). epoxies have been tried. ceramics
have
been tested. experiments continue and sooner or later amateur telescopes will
have free molded ceramic (epoxy?) mirrors. Its almost inevitable withtime.
Jerry





Kris T wrote:

I understand the largest practical lens size is around 40" with glass. well
what about some sort of self sustaining liquid lens, sort of a soap bubble
lens?

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

"RankAndFile" wrote in message . ..
Do you just want to look at your zenith?
Jamie

Or for that matter what about a large mirror made of liquid metal like
mercury. spin the mount and it will form a convex shape right, the liquid
wouldn't need to be deep.

Quite a lot of research has been caried out on large mercury mirrors
over a long period of time.
I suggest a browse for more details using: liquid mercury mirrors

Chris.B