(meteorobs) OT-Possible single station determination of meteordistance.

Chris Peterson clp at alumni.caltech.edu
Wed Dec 17 13:52:47 EST 2008


I can't really figure out from your description what the actual setup is, or 
how this would work. I do have a few observations that might prove helpful:

1) If your intent is somehow based on interferometry (as in M-M), you can't 
achieve this by combining the video signals of two cameras.

2) If you are depending on critical timing, keep in mind that the video 
cameras will be running asynchronously of each other, so you can't depend on 
timing to better than 1 frame time. That is, each camera will be seeing the 
fireball at different times.

3) Video signals are not RF, and can't be combined with a passive splitter. 
You would need some kind of delay-and-lock circuit (since the frames are not 
in sync), or a pair of frame grabbers.

4) Your camera with a 4mm lens has a pixel scale of about 260 arcseconds. 
The angular deviation of a fireball 10 miles away, with cameras 6 feet 
apart, is 23 arcseconds. The latter is about the best precision you could 
expect for a centroid calculation; it's probably far too small to use 
parallax to reliably get a distance.

5) If you're going to invest in two camera systems, why not just put the 
other one 20 miles away? It's easy to find people willing to host cameras. 
That will allow you to get much better data on the meteor, including its 
velocity and the absolute position of any terminal explosion. It will also 
allow you to get data on many more meteors, since the distance you can get 
good data is now pushed to several hundred miles.

Chris

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


----- Original Message ----- 
From: "stange" <stange34 at sbcglobal.net>
To: <meteorobs at meteorobs.org>
Sent: Wednesday, December 17, 2008 1:48 AM
Subject: (meteorobs) OT-Possible single station determination of 
meteordistance.


> Tossing this bit of thought out....after re-reading Michaelson-Morley
> interferometer stuff.
>
> If two cameras with square CCD's and identicle 4mm lenses were mounted on 
> a
> common platform about 6 feet apart and UNLIKE a range finder which you 
> could
> not adjust in time for a fireball explosion.... those cameras were 
> pre-aimed
> at a small terrestrial light source about 10 miles out and the platform 
> with
> the mounted cameras unchanged were to have their individual composite
> signals combined into a single point of light by inputting into a reversed
> RF-splitter with the output going into a computer frame grabber and
> detection software with the light spot centered in the monitor or the
> software, one could expect detection of a fireball explosion and the
> DISTANCE to that explosion could be measured by the actual displacement
> between the two images in seconds of a degree. The monitor centering is 
> only
> to make room for the different azimuths and elevations the fireball might
> occur. Those spot images can be anywhere on the screen.
>
> Magnification of the "split" image may be necessary to resolve a second of 
> a
> degree. Some correction might be needed for elevations because CCD
> cross-sections are greater than the length or width of a square CCD.
>
> If the fireball occurs ten miles distant... there will be no displacement
> between the spots.
> Beyond ten miles the displacement grows proportionally. The cameras and
> platform would need aiming skyward after the "collimation" or calibration 
> of
> the two spot images into one.
>
> YCSentinel




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