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Re: (meteorobs) Angular Speed Equations



GeoZay wrote:
> I forgot to add....a good angular speed measurement can be used to roughly 
> estimate the shower radiant position for one meteor, when combined with the 
> path length, IF you have good alignment as well. Without good alignment and 
> any intersects, it's anybodies guess.  How do you know if a visual observers 
> alignment isn't off for any one meteor? You don't. This is the reason for 
> visual observing purposes, a  known radiant location is enlargened. I 
> personally prefer multiple intersects to direct me into estimating a new 
> radiant position. I still haven't seen any practical use for angular speed 
> estimates other than shower association. Just like the speed scale I use.  

Without the angular-speed estimate you can plot the intersections of
most pairs of meteors.  Yes this will work for strong radiants, but
for weak minor showers the additional noise of false radiants can
drown out the real ones.  Apart from the path-length constraint the
radiant can be anywhere along half of the great circle of its
prolongated path (for simplicity I'm ignoring the observation errors
in the position).  Using an estimate of angular speed, be it from a
scale converted to deg/s or deg/s directly, gives a much reduced arc
where the radiant can be.  Thus the number of false radiants is
reduced and the real ones become more evident.  To reiterate, I've
been talking about plotting. 

For shower identification during counting, I just factor in the
apparent speed, path length and orientation, and radiant distance to
make shower assignment.  During a major shower there's no time for
fancy calculations.  It becomes automatic with practice.

George, you didn't say what your speed scale calibration is.  Please
can you elaborate.

Malcolm

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