FWHM vs FWHMs

Can anyone tell me what FWHMs is and how it relates to FWHM?

On Fri, 08 Apr 2005 00:16:32 GMT, "Christopher Graham"
wrote:

Can anyone tell me what FWHMs is and how it relates to FWHM?

AFAIK, "FWHMs" is the plural of FWHM (full width at half maximum), a
figure of merit that can describe different functions, but is primarily
used for Gaussians.

Have you seen a different usage?

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
On Fri, 08 Apr 2005 00:16:32 GMT, "Christopher Graham"
wrote:


Can anyone tell me what FWHMs is and how it relates to FWHM?


AFAIK, "" is the plural of FWHM (full width at half maximum), a
figure of merit that can describe different functions, but is primarily
used for Gaussians.

Have you seen a different usage?


Yes. Arne Henden, president of the AAVSO, wrote about them in an email
as if they were distinct quantities, with fwhms being the smaller of the
two. Searching the web just finds plural versions. I'm wondering if the
s is for "per second", but that doesn't make sense to me.

Can anyone tell me what FWHMs is and how it relates to FWHM?

... Arne Henden, president of the AAVSO, wrote about them in an email

as if they were distinct quantities, with fwhms being the smaller of
the
two. Searching the web just finds plural versions. I'm wondering if
the
s is for "per second", but that doesn't make sense to me.

I would guess that Arne may have been distinguishing between
the usual FWHM and a related variable which is often denoted by
the greek letter "sigma". One way to write the equation for a
gaussian looks like

f(x) = A exp(- x / 2*(sigma^2) )

where "sigma" defines the width of the gaussian peak. For
a pure gaussian,

FWHM = 2.35 * sigma

Perhaps Arne is using "FWHMs" to mean "the sigma variable
in the expression for a gaussian".

Michael Richmond