(meteorobs) Fwd: Determining Altitude & Azimuth From All Sky Cam Images (fwd)

Ken Tapping Ken.Tapping at nrc-cnrc.gc.ca
Mon Dec 7 17:05:27 EST 2009


    We can discuss this further and will pass along a writeup.

The camera image gives x,y pixel addresses that have some relationship 
with the sky. We need to know what pixels correspond with the camera 
boresight and with the zenith. We need also to know the relationship 
between radial distance from the camera boresight and angle from the 
boresight. From this we get the camera azimuth and the angle from 
boresight. We need also to know the relationship between camera azimuth 
and real azimuth.

We make star images, using long or stacked exposures. Using an ephemeris 
program we get on the screen an image of the sky at the location and time 
of the camera exposure. The ephemeris program gives us the azimuth and 
elevation of stars at the time of the exposure. We then endeavour to 
locate those stars in the camera image, and get the camera azimuth and 
angle from boresight. Then we do a massive fitting exercise to establish 
the relationship between the camera coordinates and the outside world.

A note discussing that is attached. As you might guess, this is something 
we are still working on. In the note we assume the camera is set up close 
to the zenith, so the distance  between the centre pixel and the zenith 
pixel is small.



Dr Ken Tapping

* National Research Council          |  Conseil national de recherches   *
* Herzberg Institute of Astrophysics |  Institut Herzberg d'astrophysique*
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