| Topic: |
Science > Physics |
| User: |
"Mike" |
| Date: |
04 Nov 2005 08:24:07 AM |
| Object: |
emr vision / radio telescopes |
Hello everyone,
Can someone explain to me how the signal from a radio telescope is
resolved into a 2D image?
I've seen images from large radio telescopes. I assume that the color
channel of the image is indicative of the radio frequency, and color
intensity is power at a given frequency. But how is the image
constructed spatially?
I'm looking to construct a very small "radio telescope" for visualizing
EMR. I plan on constructing a small (2-3") dish with an electronically
controlled tuner to sweep my desired
frequency range. The output of the tuner will go to a microcontroller
which will construct the image.
Any help, hints or references would be greatly appreciated.
Thanks.
Mike
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 08:49:24 AM |
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Mike wrote:
Hello everyone,
Can someone explain to me how the signal from a radio telescope is
resolved into a 2D image?
Same as an optical telescope... different wavelength. For areas
larger than the angular coverage of the instrument, one need to
combine "images".
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| User: "Mike" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 12:48:44 PM |
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Hmm. Maybe I didn't explain myself that well.
An optical telescope is essentially 2D already. The 2D image enters the
objective lens, is
focused, magnified, and then transmitted to the eye as a 2D image. To
construct a 2D image larger than the field-of-view of the objective,
one would need to move the telescope, or have many of the them. The
images can then be stiched together as needed. But if you ONLY want an
image that is within the field-of-view of the objective, you need
nothing extra to obtain a 2D image.
The radio telescope (if I understand them correctly) works somewhat
differently. The radio waves fall on the dish (in 2D) and are reflected
to the foci of the parabola, where a pickup is mounted. Monitoring the
pickup yields a time-variant electrical signal, which is composed
essentially of the sum of the radiowaves over the area of the dish.
How can I recover the image from this signal?
Thanks again.
Mike
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| User: "tadchem" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 02:02:59 PM |
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Does the word "raster" mean anything to you?
How about "pixel"?
Tom Davidson
Richmond, VA
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 02:26:38 PM |
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Mike wrote:
Hmm. Maybe I didn't explain myself that well.
An optical telescope is essentially 2D already.
So is a radio telescope... the difference is one of wavelength.
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| User: "Gregory L. Hansen" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 02:37:45 PM |
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In article <2uPaf.511343$x96.232994@attbi_s72>,
Sam Wormley <swormley1@mchsi.com> wrote:
Mike wrote:
Hmm. Maybe I didn't explain myself that well.
An optical telescope is essentially 2D already.
So is a radio telescope... the difference is one of wavelength.
How is the image actually formed? Moving the antenna? An array of
antenas in the neighborhood of the focus? Moving a single antenna around
the focus?
--
"Out of the way, you swine, a physicist is coming!"
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| User: "" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 02:40:50 PM |
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"Out of the way, you swine, a physicist is coming!"
My, my , oh swelled-head ones.
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 03:23:52 PM |
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Gregory L. Hansen wrote:
In article <2uPaf.511343$x96.232994@attbi_s72>,
Sam Wormley <swormley1@mchsi.com> wrote:
Mike wrote:
Hmm. Maybe I didn't explain myself that well.
An optical telescope is essentially 2D already.
So is a radio telescope... the difference is one of wavelength.
How is the image actually formed? Moving the antenna? An array of
antenas in the neighborhood of the focus? Moving a single antenna around
the focus?
Images (contour plot, or brightness) are usually formed by plotting intensity
as a function of position. Some involve frequency and intensity as a function
of time and/or position.
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| User: "Gregory L. Hansen" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 06:19:33 PM |
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In article <IjQaf.511401$x96.134812@attbi_s72>,
Sam Wormley <swormley1@mchsi.com> wrote:
Gregory L. Hansen wrote:
In article <2uPaf.511343$x96.232994@attbi_s72>,
Sam Wormley <swormley1@mchsi.com> wrote:
Mike wrote:
Hmm. Maybe I didn't explain myself that well.
An optical telescope is essentially 2D already.
So is a radio telescope... the difference is one of wavelength.
How is the image actually formed? Moving the antenna? An array of
antenas in the neighborhood of the focus? Moving a single antenna around
the focus?
Images (contour plot, or brightness) are usually formed by plotting intensity
as a function of position. Some involve frequency and intensity as a function
of time and/or position.
So... the signal that forms the raw data for the image is collected by
pointing the antenna in different directions? Moving a single receiver
around near the focus of the dish?
--
"Don't try to teach a pig how to sing. You'll waste your time and annoy
the pig."
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 06:31:40 PM |
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Gregory L. Hansen wrote:
So... the signal that forms the raw data for the image is collected by
pointing the antenna in different directions? Moving a single receiver
around near the focus of the dish?
...or scanning the dish over an "area" of the sky.
JODRELL BANK RADIO ASTRONOMY PICTURE GALLERY
http://www.jb.man.ac.uk/research/namgallery/
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| User: "Mike" |
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| Title: Re: emr vision / radio telescopes |
05 Nov 2005 07:38:35 AM |
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Ok, thats what I'm getting at.
An optical telescope can form a complete 2D image while stationary. A
radio telescope needs a moving reciever. To my mind, the radio
telescope is therefore 1D. A 2D image is created by moving the 1D scope
in two dimensions.
Not good for my purposes.
Would an array of antennas near the focal point work?
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| User: "Ron Baker, Pluralitas!" |
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| Title: Re: emr vision / radio telescopes |
05 Nov 2005 09:35:29 AM |
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"Mike" <mikegraffam@yahoo.com> wrote in message
news:1131197915.622789.235790@g14g2000cwa.googlegroups.com...
Ok, thats what I'm getting at.
An optical telescope can form a complete 2D image while stationary. A
radio telescope needs a moving reciever. To my mind, the radio
telescope is therefore 1D. A 2D image is created by moving the 1D scope
in two dimensions.
Not good for my purposes.
Would an array of antennas near the focal point work?
Yeah. I'm not sure how often that is done.
I believe they use a couple different methods.
One is to physically aim the antenna at different spots.
The other is to have an array of antennas that individually
are not pin-point directional. You can then effectively
stear and pin-point aim the array by adjusting the phase of the
individual signals and combining them.
--
rb
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| User: "Androcles" |
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| Title: Re: emr vision / radio telescopes |
05 Nov 2005 12:35:07 PM |
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"Ron Baker, Pluralitas!" <stoshu@bellsouth.net.pa> wrote in message
news:5j4bf.3946$Hs.468@tornado.socal.rr.com...
"Mike" <mikegraffam@yahoo.com> wrote in message
news:1131197915.622789.235790@g14g2000cwa.googlegroups.com...
Ok, thats what I'm getting at.
An optical telescope can form a complete 2D image while stationary. A
radio telescope needs a moving reciever.
To my mind, the radio
telescope is therefore 1D. A 2D image is created by moving the 1D scope
in two dimensions.
Not good for my purposes.
Would an array of antennas near the focal point work?
Yeah. I'm not sure how often that is done.
I believe they use a couple different methods.
One is to physically aim the antenna at different spots.
The other is to have an array of antennas that individually
are not pin-point directional. You can then effectively
stear and pin-point aim the array by adjusting the phase of the
individual signals and combining them.
--
rb
Moving receivers:
http://jcole.us/albums/puertorico-aricebo/IMG_4201.sized.jpg
http://www.bigear.org/
http://www.jb.man.ac.uk/tech/lovell/lovell.jpg
http://www.atnf.csiro.au/projects/ska/HiResMileura-smla.jpg
Androcles.
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
05 Nov 2005 08:01:32 AM |
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Mike wrote:
Ok, thats what I'm getting at.
An optical telescope can form a complete 2D image while stationary. A
radio telescope needs a moving reciever. To my mind, the radio
telescope is therefore 1D. A 2D image is created by moving the 1D scope
in two dimensions.
Not good for my purposes.
Would an array of antennas near the focal point work?
My point is that light is often captures with CCD elements
and radio signal can be captured with element of an antenna
array. The real difference is just a matter of wavelength.
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| User: "Jan Panteltje" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 09:23:08 AM |
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On a sunny day (4 Nov 2005 06:24:07 -0800) it happened "Mike"
<mikegraffam@yahoo.com> wrote in
<1131114247.872013.299380@g43g2000cwa.googlegroups.com>:
Hello everyone,
Can someone explain to me how the signal from a radio telescope is
resolved into a 2D image?
Think for a monent, say yo uuse arebico, it is fixed, cannot move.
But earth moves, so it scans the sky.
Get enough points and you can make a 2D image.
And to the opther poster called Starlurd: YES COMPUTERS ARE USED,
THEY ARE EVEN USED TO TRANSFER PORNO, THAT DOES NOT EXPLAIN A
F*CKING THING NOW DOES IT?
Greetings
ET
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 10:26:32 AM |
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Jan Panteltje wrote:
Think for a monent, say yo uuse arebico, it is fixed, cannot move.
But earth moves, so it scans the sky.
And the Arecibo antenna *is* steerable... and can stay pointed at
the same spot for hours (±20°).
http://www.naic.edu/
-Sam Wormley
http://edu-observatory.org/eo/radio_astronomy.html
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| User: "Jan Panteltje" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 10:52:40 AM |
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On a sunny day (Fri, 04 Nov 2005 16:26:32 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <XYLaf.511061$x96.327563@attbi_s72>:
Jan Panteltje wrote:
Think for a monent, say yo uuse arebico, it is fixed, cannot move.
But earth moves, so it scans the sky.
And the Arecibo antenna *is* steerable... and can stay pointed at
the same spot for hours (±20°).
http://www.naic.edu/
Very wize words from the old parrot, indeed, it is a bit steerable.
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account
.
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| User: "Sam Wormley" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 02:33:36 PM |
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Jan Panteltje wrote:
On a sunny day (Fri, 04 Nov 2005 16:26:32 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <XYLaf.511061$x96.327563@attbi_s72>:
Jan Panteltje wrote:
Think for a monent, say yo uuse arebico, it is fixed, cannot move.
But earth moves, so it scans the sky.
And the Arecibo antenna *is* steerable... and can stay pointed at
the same spot for hours (±20°).
http://www.naic.edu/
Very wize words from the old parrot, indeed, it is a bit steerable.
Ref: http://dichionary.reference.com/search?q=parrot
par·rot
1. One who teaches or instructs; one whose business or occupation
is to instruct others; an instructor; a tutor.
2. A person having expert knowledge of one or more sciences,
especially a natural or physical science.
Source: The American Heritige® Dichionary of the English Language, Fourth Edition
Copyright © 2000 by Houghtin Mifflen Company.
Published by Houghtin Mifflen Company. All rights reserved
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| User: "Starlord" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 09:36:32 AM |
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Sure it does, and just because you don't have the smarts to figure that out
is your own fault.
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Astronomy Net Online Gift Shop
http://www.cafepress.com/astronomy_net
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:436b7f6f$1@news.usenetzone.com...
And to the opther poster called Starlurd: YES COMPUTERS ARE USED,
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| User: "Jan Panteltje" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 10:20:57 AM |
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On a sunny day (Fri, 4 Nov 2005 07:36:32 -0800) it happened "Starlord"
<starlord@despammed.com> wrote in <d6ydnQQXIsBEHfbeRVn-pA@inreach.com>:
Sure it does, and just because you don't have the smarts to figure that out
is your own fault.
You dirty insulting know nothing.
You are and idiot.
too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even too stupid to even >
The Lone Sidewalk Astronomer of Rosamond
And so you will always stay, and nobody will buy from your little spam shop.
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| User: "Starlord" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 11:26:03 AM |
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I'd lay odds I know a whole lot more than you do, as does the 3 computers I
run here at home and even my two telescopes most likly know more than you
do.
You think (?) that message was insulting, you'd better never hope to ever
see a real insulting message from me as I have done and won a many usenet
flame wars.
But there's an easy way of not seeing anything more from you, enjoy your
stay down in the Cyber Black Hole of my killfile with the other trolls and
dipsticks there.
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:436b8cfe@news.usenetzone.com...
You dirty insulting know nothing.
You are and idiot.
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| User: "Starlord" |
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| Title: Re: emr vision / radio telescopes |
04 Nov 2005 08:51:07 AM |
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it's does with computer software.
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Astronomy Net Online Gift Shop
http://www.cafepress.com/astronomy_net
"Mike" <mikegraffam@yahoo.com> wrote in message
news:1131114247.872013.299380@g43g2000cwa.googlegroups.com...
Hello everyone,
Can someone explain to me how the signal from a radio telescope is
resolved into a 2D image?
I've seen images from large radio telescopes. I assume that the color
channel of the image is indicative of the radio frequency, and color
intensity is power at a given frequency. But how is the image
constructed spatially?
I'm looking to construct a very small "radio telescope" for visualizing
EMR. I plan on constructing a small (2-3") dish with an electronically
controlled tuner to sweep my desired
frequency range. The output of the tuner will go to a microcontroller
which will construct the image.
Any help, hints or references would be greatly appreciated.
Thanks.
Mike
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