(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
Hi,
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.
Regards,
Ken
--
Dr Ken Tapping
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