[no subject]

[Jan Hollan <jhollan@amper....muni.cz>]

Dear Nobleperson,

We've got a hint from Petr Harmanec, that you might know most on the
problem of calibration of astronomical radiometry.

I wrote some text on quantities and units in astronomical photometry in
Czech (serving as a proposal for normalization) and I gave there the
flux for a star of bolometric faintness of 0 mag as 2.48 E-8 W.m-2.
The value is from the Allen's Astrophysical Quantities, and I claim it as
being uncertain by several per cent. 

Of course, that is quite a large uncertainty. One might wonder, if it
would be not possible to define the value once for ever (e.g., for
simplicity as equal exactly to 2.5E-8 W.m-2). Then at least the bolometric
faintness of Sun could be given with the same uncertainty, as the changing
solar "constant" is known.

My colleague Zdenek Mikulasek is making final revision of his textbook on
the Physics of Stars (in Czech), and a calibration of this kind is vital
for his text, and many accompanying excersizes.  

Could you please send me a note on the zero level of the bolometric scale? 

Yours sincerely,
                   Jan

PS. 

By "Faintness" I mean the quantity measured in magnitudes (1 mag, dmag,
cmag or mmag is always unit in our Czech texts, and we use an another term
for the quantity). "Faintness" is a possible name of that quantity in
English. If "magnitude" would be the name of the logarithmic quantity,
another name for its unit would be needed (pogson?), as it is really
inconvenient to have no unit at all.


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                                Jan Hollan
              N. Copernicus Observatory and Planetarium in Brno
Kraví hora 2, CZ - 616 00 Brno                        +420 (5) 41 32 12 87

                                   home:
Lipová 19, 602 00 Brno                                         43 23 90 96

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Panská 9, 602 00 Brno, Czechia                  fax:  +420 (5) 42 21 05 61

e-mail: hollan@ped....cz             http://astro.sci.muni.cz/pub/hollan
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