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Re: Magnitude Estimates
At 12:18 PM 5/20/96 -0400, Lew Gramer wrote:
>I tend to call them as I see them, at half-mag or not. I notice that half mags
>are more common in the range 3 to 0 (not too faint for clear impressions, but
>not too bright to be an uncommon occurence.) BTW, the AAVSO accepts visual
>observations on variables with amplitudes of less than 1 magnitude, don't
they?
You're right on the AAVSO observations, which often are measured in tenths
of a magnitude for visual observations. And for those who have never
observed variables, it is surprising at how accurate a variable star
estimate can be made. This is a reason why this amateur data is highly
sought by NASA, ESA, etc. for their observing missions.
But, in relating it to meteor observing, two points are very different. A
variable star observer has time on their side to make the observation. The
star does not become invisible in less than a second. Second, as a result of
this, they can make a magnitude estimate and then double-check it as many
times as they like. Again, meteor observers do not have this luxury, except
possibly from memory which may introduce further errors, and if you're like
me, can't be relied on. :)
>I guess a lot of it comes down to the proximity of good comparison stars.
This is also true as the AAVSO observing charts have comparison stars very
close to the variable, often in the same FOV of the binocular/telescope. The
closer the comparison star, the easier it becomes to make an accurate
estimate. When a meteor appears, it is possible that the comparison star is
located halfway or more across the sky from the meteor, which makes the
estimate more difficult to make.
Concerning an "error term" a convenient way for an individual to check their
estimates is through a magnitude distribution for sporadics and all active
showers. Of course, this is only possible if a sufficient number of meteors
are observed, and is not highly accurate, but it can provide some hints on
how a person is doing.
mark