Roman telescope

On 22 Feb 2004 21:08:33 GMT, (Jon Isaacs) wrote:

Are you sure? I poked around the internet a bit but I did not find evidence
that Silver nitrate was known at that time.

Well, it is trivial to make silver nitrate. Making nitric acid is also easy, but
I admit I had to look up the details- it's been a long time since I took
chemistry.

_________________________________________________

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

"starman" wrote in message
...
Bernardz wrote:

I am writing a what-if history fiction and need some help.

If you were suddenly dropped in Rome say in 200 CE and you needed to
build a telescope for mass production. What sort of telescope would you
make and what would it look like?

You would essentially be limited to what Galileo used centuries later, a
very basic refractor telescope using one convex objective lens, perhaps
an inch (25mm) in diameter and a smaller concave eyepiece lens located
at the focal length of the objective. The lenses would be assembled in a
metal or paper tube. The hard part would be making optical quality glass
in 200-CE. It took about 5000-years from the accidental discovery of
glass by the Phoenicians, (in the sand under their cooking fires) to the
first lenses in the 16th century. You would need a small blast furnace
to make the glass from sand. Each lens would be shaped by grinding two
glass disks together with some natural abrasive (sand?) and water
between them. The abrasive would have to be graded to various sizes by
letting it settle through a water column. You would start the grinding
with the coarse grade and proceed to the finest, just like it's done
today. Finally the lens would be polished, probably using bees wax to
make a 'lap' with some kind of very fine abrasive or 'rouge' as the
polishing agent, which might be hard to find in that era.
In all, it would be a very challenging project and I doubt it would be
practical to mass produce them. However, even if you made just one
telescope in Roman times it could change the course of history.
There were earlier lenses made of rock-crystal. However 'mass production'
would seem unlikely for these.
Given that data can presumably be taken back, the simplest solution, would
seem to be a speculum metal based Newtonian. Copper and tin, were readily
available, and being relatively 'mass produced' allready, and though the
mirrors would degrade quite quickly, the processes would all be ones that
any jeweler of the time would probably know allready.

Best Wishes

"starman" wrote in message
...
Bernardz wrote:

I am writing a what-if history fiction and need some help.

If you were suddenly dropped in Rome say in 200 CE and you needed to
build a telescope for mass production. What sort of telescope would you
make and what would it look like?

You would essentially be limited to what Galileo used centuries later, a
very basic refractor telescope using one convex objective lens, perhaps
an inch (25mm) in diameter and a smaller concave eyepiece lens located
at the focal length of the objective. The lenses would be assembled in a
metal or paper tube. The hard part would be making optical quality glass
in 200-CE. It took about 5000-years from the accidental discovery of
glass by the Phoenicians, (in the sand under their cooking fires) to the
first lenses in the 16th century. You would need a small blast furnace
to make the glass from sand. Each lens would be shaped by grinding two
glass disks together with some natural abrasive (sand?) and water
between them. The abrasive would have to be graded to various sizes by
letting it settle through a water column. You would start the grinding
with the coarse grade and proceed to the finest, just like it's done
today. Finally the lens would be polished, probably using bees wax to
make a 'lap' with some kind of very fine abrasive or 'rouge' as the
polishing agent, which might be hard to find in that era.
In all, it would be a very challenging project and I doubt it would be
practical to mass produce them. However, even if you made just one
telescope in Roman times it could change the course of history.
There were earlier lenses made of rock-crystal. However 'mass production'
would seem unlikely for these.
Given that data can presumably be taken back, the simplest solution, would
seem to be a speculum metal based Newtonian. Copper and tin, were readily
available, and being relatively 'mass produced' allready, and though the
mirrors would degrade quite quickly, the processes would all be ones that
any jeweler of the time would probably know allready.

Best Wishes

Well, it is trivial to make silver nitrate. Making nitric acid is also easy,
but
I admit I had to look up the details- it's been a long time since I took
chemistry.

I sit easy using modern techniques or is it easy using the technologies that
existed at the time? From my point of view, "being dropped into 200BC"
precludes the ability to look up how to make Silver Nitrate in a book.

jon

Well, it is trivial to make silver nitrate. Making nitric acid is also easy,
but
I admit I had to look up the details- it's been a long time since I took
chemistry.

I sit easy using modern techniques or is it easy using the technologies that
existed at the time? From my point of view, "being dropped into 200BC"
precludes the ability to look up how to make Silver Nitrate in a book.

jon

"Mike Ruskai" wrote in message t.earthlink.net...
On Sun, 22 Feb 2004 21:24:19 +1100, Bernardz wrote:

I am writing a what-if history fiction and need some help.

If you were suddenly dropped in Rome say in 200 CE and you needed to
build a telescope for mass production. What sort of telescope would you
make and what would it look like?

A Newtonian, for certain. It's by far the simplest to make, and would
outperform any refractor with the materials available.

It would likely look much the same as a home-built Dobsonian-mounted
Newtonian does today.

If I were dropped in, knowing what I know today, I would make a
Herschellian reflector on a Dobsonian mounting. I expect that I would
have the best luck using natural glass (obsidian) for making an f/10
or so concave sphere using the walk-around-the-barrel grinding and
polishing process with graded sand for abrasive and jewelers rouge for
polishing on pitch. One could probably could get pieces of obsidian
big enough for a 6", certainly a 4". The best manmade glass available
might also be good enough for a mirror blank, particularly if you had
the glassmaker take extra pains to cool it slowly enough to be well
annealed. Chemical silvering would be quite feasible using alchemical
ingredients known at the time. To make eyepiece lenses I would use
natural optical quality minerals. Quartz crystal has excelent optical
properties and has been worked to optical finish by jewelers or other
artisans from this era and even earlier. Calcium fluorite crystal
might even be findable. From these natural crystals I would grind and
polish simple biconvex lenses. This is all you need to make a
Herschellian reflector. Would work great in a simple Dobsonian
mounting. No Teflon or Formica would be available, but waxed wood on
ivory could be used to make a pretty decent bearing surface.
Clif Ashcraft

Chemical silvering would be quite feasible using alchemical
ingredients known at the time.

This is the one I doubt. Do you have a reference or something that indicates
that the Roman at least knew about nitric acid? It is true that saltpeter
exits naturally, but it takes more than that to make nitric acid.

jon
Jon

Now you're on the right track - polished brass mirror, which they did.
They probably experimented with these and realised a polished brass inferior
curve would bring light (and heat) to a focus, which the Greeks knew, but
lacking
any principle or means to apply an "eyepiece" at the focal point, all progress
probably stalled.

Then lacking glass pure enough to fabricate a good lens (we assume this was the
case because no archaeological evidence says otherwise) ... we assume no
refractors issued forth either, or they certainly would have used them (on the
seas and in land military campaigns).

Ive seen optical systems with both gold and polished brass (and other metal)
mirrors. They cast a characteristic 'glow' to star images. Vega looks perfectly

'golden'? It's kind of humorous, frankly. Brings to mind rose coloured glasses
from the sixties but with a different hue of course. Gold and platinum mirrors
etc
in such systems are used of course because of their very definate filtering
properties, and because they are chemically semi-inert in hostile environments
vs coated glass or ceramic mirrors.

Silvered glass from the silver nitrate process sometimes must be buffed back to
a
polish within 24-36hours. This was a common complaint of early atm's ...

Jerry


fstops wrote:

Bernardz wrote in
news:MPG.1aa32e61522659a398991e@news:

I am writing a what-if history fiction and need some help.

If you were suddenly dropped in Rome say in 200 CE and you needed to
build a telescope for mass production. What sort of telescope would you
make and what would it look like?


I'd build a newtonian reflecting telescope with a metal mirror. The romans
certainly could cast a bronze disk a few inches in diameter. You would have
to experiment with abrasives to grind and polish it. Yeah, the reflectivity
would be low, and it would have to be repolished every couple months as it
tarnished but it would work. Maybe a light coating of olive oil could keep
it from tarnishing ha. Depends on how good the optics would have to be. If
cost were no object, gold or silver could be used. Gold would not tarnish.
Maybe you could use Gold for the secondary mirrors.
Bryan

The Romans may very well have known about Nitric Acid but under a different
name. It was definaltely known in the Middle Ages as Aqua Regia this material
made up of Hydrochloric Acid and Nitric Acid was able to dissolve Silver and
Gold. This Acid was available through the then primitive methods of making
fertilizer. It was also used in making dyes and I know the romans had methods
to dye cloth. So Silvering on Glass might not be impossible. Of course going
back in time you would be able to jump start the whole chemical industry with
just some very basic knowledge of chemistry. Acids and Bases were really not
all that well understood then there is the whole field of Organic Chemistry to
choose from

Clear Skies
Dwight L Bogan




Chemical silvering would be quite feasible using alchemical
ingredients known at the time.

This is the one I doubt. Do you have a reference or something that indicates
that the Roman at least knew about nitric acid? It is true that saltpeter
exits naturally, but it takes more than that to make nitric acid.

jon
Jon

On 23 Feb 2004 00:06:11 GMT, (Jon Isaacs) wrote:

I sit easy using modern techniques or is it easy using the technologies that
existed at the time? From my point of view, "being dropped into 200BC"
precludes the ability to look up how to make Silver Nitrate in a book.

Well, I guess it all depends on the level of knowledge you carry. Of course,
there is always the possibility of having a little advance warning that you are
going to be dropped somewhen g. I already knew how to make silver nitrate- I
didn't look that up. What I checked was how to make nitric acid. For all I know,
that knowledge may have been available to ancient Romans, anyway.

My point was only that the technologies possessed by the Romans were more than
adequate to make a concave mirror and to silver it. That is, I could probably go
to a silversmith and an apothecary and find everything necessary. I presume that
our time travelers has the basic knowledge required. As others have pointed out,
a telescope with a metal mirror is another option.

Producing a thick piece of glass of reasonable optical quality seems more
difficult with Roman technology than producing a silvered mirror.

_________________________________________________

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