Kurt wrote:
Ferris
Schaefer simplified
Olof-Carlin rule-of-
rule thumb Diff.
NELM Ba
4.0 18.0 18.0 +0.0
4.5 18.7 18.5 +0.2
5.0 19.3 19.0 +0.3
5.5 20.0 19.5 +0.5
6.0 20.8 20.0 +0.8
6.5 21.7 20.5 +1.2
7.0 22.9 21.0 +1.9
7.5 24.9 21.5 +3.4

Schaefer revised by Olof-Carlin
Ba = 21.58 - 5 log(10^(1.586-lim_mag/5)-1)
Ferris proposed simplified rule of thumb
Ba = lim_mag + 14

You might try, as an intermediate rule of thumb, if you can juggle
figures with reasonable facility: Halve the NELM, subtract 1, square,
and add 17. I understand that for most people, this won't seem like
much fun (sorry!), but it yields the following values of Ba:

NELM Ba Diff
4.0 18.0 +0.0
4.5 18.6 -0.1
5.0 19.3 +0.0
5.5 20.1 +0.1
6.0 21.0 +0.2
6.5 22.1 +0.4
7.0 23.3 +0.4
7.5 24.6 -0.3

I'm mostly with Tony; I'm dubious as to how useful this will be
in practice. But I did find it an interesting mental exercise to
find a reasonably simple fit.

Brian Tung
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