(meteorobs) Origin of ZHR is elusive

[Richard Taibi]

A few kind list members made some suggestions about where I might find the 
answer to two questions.  Who thought of the concept of ZHR?  When was it 
thought of?

JB Sidgwick's Observational Astronomy for Amateurs had promising subsections 
in Chapter 15, "Meteors."  And he had a good bibliography for the subject 
too.  Perusing Sidgewick's book was my first goal for a trip to the Library 
of Congress.  I also hoped to find at least two references in the 
bibliography.

Inspection of JBS' references seemed to suggest that they were articles 
about meteor velocities, meteor radiants, meteor heights in the atmosphere, 
and real paths through the atmosphere.  Most titles were specific enough to 
rule them out as possibilities for the origin of ZHR.  However, with the 
limited time I had, two article titles were sufficiently vague that they 
might have been what I searched for.

The first was JG Porter's article, "The Reduction of Meteor Observations," 
from 1937. However, the reduction that Porter had in mind was how to find 
the real paths of meteors in the sky when two observers record meteors.  The 
second article, Opik's "Statistical Method of Counting Shooting Stars..." 
(1922) proved to be about a similar topic and a method that he termed the 
"double count method" where two or more observers would be employed using a 
rigorous methodology to reduce errors.

So, I found no mention of ZHR in these early articles, and no mention in 
Sidgewick's references' titles.  However, there were facets of methodology 
currently employed to find limiting magnitudes.  Faced with having little 
time remaining before close of library, I needed a more efficient way to 
survey titles of articles in astronomical literature.  A librarian referred 
me to Astronomischer Jahresbericht because the editors list titles published 
each year according to subject areas, like Meteors.  It was also a likely 
source because AJ functioned 1899-1968.

I had time to check AJ for 1941, 42, 1949-50, and 1955, the year Sidgewick's 
book was published.  Briefly, no title included the term "ZHR" in it and 
most titles seemed unlikely to have the concept in the articles.  Frequent 
topics in the 1941-1950 time period seemed to be about meteor velocities and 
using radar and radio to deduce meteoric properties.  The 1955 volume of AJ 
also contained no titles suggesting that referenced articles contained the 
term ZHR.  Meteor velocities was still an important topic, as was use of 
meteor ionization trails for radio communication.  US and English authors 
were concerned with the physics of meteors and the use of instrumentation 
lately developed in World War 2 to research meteors.  The 1955 AJ contained 
articles by Czech authors that were more about using visual observation 
methods as opposed to US/English use of technology to do research.  My 
survey of AJ titles suggested that answers to my ZHR questions were probably 
in articles by authors who did not have access to the high technology of the 
1950s, i.e., by non-US or English professional astronomers.  So, people like 
Whipple, Opik, etc were unlikely originators of ZHR, as creative and 
resourceful as they were.  Yet, someone had developed the concept by 1955 
because it is in Sidgewick's book published in '55.

So, to paraphrase what the TV show used to proclaim, the Truth is Still Out 
There.  My day's research may help narrow the search somewhat, I hope.  
"ZHR" originated before 1955, by someone who was not able to access the 
cutting edge of technological methods to do meteor research, but, who had 
considerable mathematical sophistication. Who does that suggest to our list 
members?  Where would that person's research have been published?  I look 
forward to your ideas.

Best wishes,  Rich