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

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?
JP

In sci.physics 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).

Making mirrors can be relatively simple.
You can make near-perfect mirrors easily up to 12-18" or so in the garage
cheaply and easily using relatively inexpensive materials (a round
mirror-shaped bit of glass, some assorted abrasives, and some others.)
As you go much over 12", the glass starts getting expensive.

Google for
dobson mirror pitch
For lots of information.


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.

It won't work very well, due to diffraction at the end of the tubes, the
lengths needed would be horrendus.
The cost would be tens of thousands of times, for a poorer result.

--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
To do is to be
To be is to do
Do be do be do do

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).

1) You don't know anything about the optics of imaging or the
physics of information.

2) Phase information (collector span) is more important than
intensity information (collector area). That is why the two Keck
telescopes on Mauna Kea are united into an optical interferometer.

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.

3) You don't know anything about aberrations, either, or numerical
aperture.

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?
JP

Uncle Al will tell you why not,

http://w0rli.home.att.net/youare.swf
http://www.mazepath.com/uncleal/sunshine.jpg

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

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

About as useful as a usenet message with no body!
Try some dehydrated water, you may have seen the crust in a boiled dry
kettle.
On Wed, 27 Aug 2003 23:10:52 +0200, John VanSickle
scribed these bits:



X X
X
X X

Jan Panteltje wrote in message ...
[snip]
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.
[snip]

Photomultipliers are pretty big to line up 1000 of them in any
useful fashion.

CCDs are already way ahead of you. Even the low end CCD cameras
these days have "electronic" magnification of several powers.

You can also do stuff like doing software corrections of minor
flaws in the CCD, feed it to image enhancement fairly directly,
build CCDs that are sensitive to different wavelengths, etc.
Socks

In sci.physics, Octa Ex

wrote
on Thu, 28 Aug 2003 07:02:31 GMT
:
About as useful as a usenet message with no body!
Try some dehydrated water, you may have seen the crust in a boiled dry
kettle.

That's probably calcium carbonate, not dehydrated water. :-)

On Wed, 27 Aug 2003 23:10:52 +0200, John VanSickle
scribed these bits:



X X
X
X X


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

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?
JP


Bet I could guess the way you would explain how Omar Khayyam
calculated the length of a year *grin*.

Seriously though virtual optics are the way to go if you can afford
the equipment. I doubt if a home hobbyist could build a receiver
that was aligned accurately enough to gather the raw data before post
processing.

On a sunny day (28 Aug 2003 08:02:03 -0700) it happened
wrote in
:

Jan Panteltje wrote in message ...
[snip]
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.
[snip]

Photomultipliers are pretty big to line up 1000 of them in any
useful fashion.
Yep.

CCDs are already way ahead of you. Even the low end CCD cameras
these days have "electronic" magnification of several powers.
Yes, but that is just electronic overscan, they expand from less pixels, say
your sensor is 800x600, then they use an 640x480 area and call it
magnification.
This however has then bigger pixels for the same screen size.
(The real resolution stays the same, not counting lens effect, so
you will not really get more detail).


You can also do stuff like doing software corrections of minor
flaws in the CCD, feed it to image enhancement fairly directly,
Yes I know my CDD / CMOS sensor stuff, in the CMOS each pixel is
compensated electronically else they would look really bad (all different).
(The gain is set for each pixel seperately).
Of cause later in software you can compensate for geometric errors to a
certain extend.
Lenses (and complicated optics like zoom stuff) cause a rather high
geometric distortion.

build CCDs that are sensitive to different wavelengths, etc.
Socks
Most semiconductor devices are also sensitive in the infrared (on the short
wave length side, so close to light).
In fact in your camera there is likely an IR filter to compensate for that.

I had a photo multiplier from the red channel of a flying spot (film)
scanner.
Since the source was sort of green, it had to be really sensitive to get
any signal.
These days there are smaller and better ones.
I REALLY do not know what would be more sensitive, the best photo diode, or
a huge photo multiplier, but I think the last (without proof).
JP