From Wikipedia, the free encyclopedia Zenithal Hourly Rate
Zenithal Hourly Rate
Example: If 20% of the observer’s field of view were cov-
ered by clouds, k would be 0.2 and F would be 1.25. The
observer should have seen 25% more meteors, therefore
we multiply by F = 1.25.
r6.5 − lm
This represents the limiting magnitude correction
factor. For every change of 1 magnitude in the limiting
magnitude of the observer, the number of meteors ob-
served changes by a factor of r. Therefore we must take
this into account.
The 2010 Perseids over the VLT
Example: If r is 2, and the observer’s limiting magnitude
In astronomy, the Zenithal Hourly Rate (ZHR of a meteor
ZHR) is 5.5, we will have to multiply their hourly rate by 2 (2
shower is the number of meteors a single observer would to the power 6.5-5.5), to know how many meteors they
see in one hour under a clear, dark sky (limiting apparent would have seen if their limiting magnitude was 6.5.
magnitude of 6.5) if the radiant of the shower were at the
zenith. The rate that can effectively be seen is nearly al- sin(hR)
ways lower and decreases the closer the radiant is to the This represents the correction factor for altitude of
horizon. the radiant above the horizon (hR). The number of mete-
ors seen by an observer changes as the sine of the radiant
The formula to calculate the ZHR is: height in degrees.
Example: If the radiant was at an average altitude of 30°
during the observation period, we will have to divide the
observer’s hourly rate by 0.5 (sin 30°) to know how many
meteors they would have seen if the radiant was at the
where
zenith.
See also
represents the hourly rate of the observer. N is the • List of meteor showers
number of meteors observed, and Teff is the effective ob-
servation time of the observer.
External links
Example: If the observer detected 12 meteors in 15 min- • North American Meteor Network (NAMN)
utes, their hourly rate was 48. (12 divided by 0.25 hours).
This represents the field of view correction factor, where
k is the percentage of the observer’s field of view which
is obstructed (by clouds, for example).
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Categories: Meteoroids, Observational astronomy
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From Wikipedia, the free encyclopedia Zenithal Hourly Rate
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