Telescope without lens or mirrors, is this a usable idea?

On a sunny day (Thu, 28 Aug 2003 02:59:59 GMT) it happened Alan Moore
wrote in
:

On Wed, 27 Aug 2003 20:06:50 GMT, Jan Panteltje
wrote:

Hi, was looking at mars, and of cause it is extremely bright, but I do not have a big telescope.
So no detail really...
Then I started thinking, making my own mirror, a big job, a new hobby, and it will take me years
to gettings right (if I get it at all working).
Then started thinking, wow, I had this big photo multiplier, extremely sensitive,
SOME of these can detect a single photon (so they say).
Now what if you took say a thousand of these, and had them all in a line, and each one look at mars
through a thin tube, so only the photons from the direction of that tube would be seen.
Align the tubes so it forms a scan line.
Then just wait for mars to pass, that would give a picture....
1000 vertical resolution, horizontal atmosphere troubles could be integrated, would be slow scan.
(Well you could follow mars slowly too, to slow down the scan).
The tubes would have to be very accurate, but why not?

Do some math on how accurate your tube alignment would have to be,
then consult a machinist as to how this accuracy could be achieved. I
think you'll find mirror grinding easier. In fact, I suspect that
you'll find it easier to design and grind an achromatic lens than what
you propose.

That said, I believe some people have done astro-photography with
single line CCD sensors, using a pinhole and allowing the earth's
rotation to do the perpendicular scan, but that was pretty low
resolution stuff. For planetary work, you'd have to put your "pinhole"
many miles from your sensor.

Al Moore

No no, not pinhole (that would be 'camera obscura', like a lens).
I mean a real tube, diameter could be microns.
Problem is to the interfacing with a rather wide photomultiplier.
In old hologram making you could shine the laser on a drop of mercury,
to spread the beam out.
Maybe something similar could be done with the light out of the tube.
Or maybe a semiconductor device / bolometer or whatever, maybe glasfibers
too.
If you wanted to be fancy use a carbon nano tube ;-)
Not sure how much if any light would pass through that.
Yes the calculations, I will give this some more attention.
Regards
Jan

John VanSickle wrote in message ...

http://www.buydehydratedwater.com

"Jan Panteltje" wrote in message
...

No no, not pinhole (that would be 'camera obscura', like a lens).
I mean a real tube, diameter could be microns.

The problem has been mentioned already. A very thin tube will only
let through diffuse illumination due to diffraction. You need your tubes
diameters to be greater than the incident light's wavelength and accordingly
very long (and straight) to resolve something like Mars features.

, in article , wrote:
(...)
CCDs are already way ahead of you. Even the low end CCD cameras
these days have "electronic" magnification of several powers.
(...)
My impression, since there is still optical magnification being
used in such devices is that this "magnification" is nothing more than
resampling, and as such it is inferior to optics in that it can't bring
out more detail. The distance between elements of the CCD, IOW, is
constant. The point behind using resampling in the camera itself could
only be to save memory, because otherwise you would be better off doing
the resampling on the computer.

'' wrote:

, in article , wrote:
(...)
CCDs are already way ahead of you. Even the low end CCD cameras
these days have "electronic" magnification of several powers.
(...)
My impression, since there is still optical magnification being
used in such devices is that this "magnification" is nothing more than
resampling, and as such it is inferior to optics in that it can't bring
out more detail. The distance between elements of the CCD, IOW, is
constant. The point behind using resampling in the camera itself could
only be to save memory, because otherwise you would be better off doing
the resampling on the computer.

Just one small point. You can easily show that on chip integration
(analog) has superior SNR to digital integration off chip.

Chuck
--
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons

From: Chuck Simmons
Date: Mon, 01 Sep 2003 16:55:01 GMT
'' wrote:

, in article nntp:/c7976c46.0308280702.3254ae85@posti
ng.google.com , wrote:
(...)
CCDs are already way ahead of you. Even the low end CCD cameras
these days have "electronic" magnification of several powers.
(...)
My impression, since there is still optical magnification being
used in such devices is that this "magnification" is nothing more than
resampling, and as such it is inferior to optics in that it can't bring
out more detail. The distance between elements of the CCD, IOW, is
constant. The point behind using resampling in the camera itself could
only be to save memory, because otherwise you would be better off doing
the resampling on the computer.

Just one small point. You can easily show that on chip integration
(analog) has superior SNR to digital integration off chip.

Yeah, I suppose, but I doubt that's how it's done. It seems to be a
monstrous task to orchestrate analog signals at variable magnifications.

Yes, it's a good idea and it's possible and probably has been done
already? I must check this one.


Let me explain, there is an exciton made inside silcon semiconductors
that is an analog to hydrogen, last I read they had excitonic carbon,
if they have excitonic oxygen by now then I'd say someone is working
on excitonic water.

A Google on excitonic molecules may do the trick.

John Devers wrote:

Yes, it's a good idea and it's possible and probably has been done
already? I must check this one.

Let me explain, there is an exciton made inside silcon semiconductors
that is an analog to hydrogen, last I read they had excitonic carbon,
if they have excitonic oxygen by now then I'd say someone is working
on excitonic water.

A Google on excitonic molecules may do the trick.

You are a spewing idiot and you read nothing. Provide a citation in
counterpoint. Randomly bundling adjectives and nouns only works in
the Liberal Arts, social advocacy, Enviro-whinerism, psychology,
politics, advertising, bunko, and religion. Even the Liberal Arts can
be induced to vomit,

http://www.physics.nyu.edu/faculty/sokal/

Uncle Al says, "Possessing great powers demands ablating great
weaknesses."

--
Uncle Al
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)

Followups.

In sci.physics, John Devers

wrote
on 13 Sep 2003 07:38:38 -0700
:
Yes, it's a good idea and it's possible and probably has been done
already? I must check this one.


Let me explain, there is an exciton made inside silcon semiconductors
that is an analog to hydrogen, last I read they had excitonic carbon,
if they have excitonic oxygen by now then I'd say someone is working
on excitonic water.

A Google on excitonic molecules may do the trick.

OK, dumb question. What's the difference between excitonic carbon
and the regular variety?

A Google search on "excitonic carbon" coughed up

http://www.nanotube.org/abs/LangeveldF.html

which seems to be a rather esoteric (and apparently
theoretical) experiment. However, an "excitonic" atom
would quite unstable, apparently, reverting to the ground
state after a time.

It's also far from clear what temperature is required.

--
#191,
It's still legal to go .sigless.