[vsnet-chat 890] Re: Magnitudes, sequences, etc.

[Taichi Kato <tkato>]

Re: [vsnet-chat 888]
Arne Henden wrote:

> There are a few commercial software packages, of course, that do decent
> photometric extractions.

   Readers probably wish to know the name of softwares, their characteristic
etc.

> IRAF/DAOPHOT etc. are available free, with a steep learning curve.

   Regarding amateur photometrists, I've heard many of them find difficulties
with IRAF (first the user must install Linux -- it's already a hard task
for a pure Win95 user).  People complain command prompt also looks unfriendly.
I haven't heard any our domestic amateur who has gone so far as to handle
DAOPHOT.  The learning curve doesn't look so steep -- of course, this may
be a result of the different degree of communication of amateur and
professional photometrists between your country and mine.  The manual in
English also looks hard to overcome.

>   Your experience at Ouda reminds me of typical Midwestern U.S. observing,
> but I don't remember extinction changing that quickly, especially if it
> stays clear.  We don't see that here in Flagstaff.

   Japan is situated east to the Asia Continent.  Plenty of rain, occasional
passages of typhoons, the western part of Japan almost totally covered
by clouds and snow during winter.  The only astronomical quiality photometric
nights I have experienced were met in Tokyo district in winter.  During other
seasons, we usually have to search a break in clouds.  On rare quasi-
photometric nights, I usually used to obtain as many images for VSNET charts.

    Nova sequence photometry: if the sequence is intended for the use of
visual observers, removing neibouring stars may introduce some biasas, because
visual observers usually use combained magnitudes to their eyes.  It would
be therefore wise to adopt the effecting aperture size of a human eye --
I suspect it's an order of 5-10 arcsec, depending on the magnification
(low power produces a larger effective aperture).  A good example may be
RU Peg, for which most observers report resolved magnitudes; EF Peg, only
large aperture observers can do; FG Sge, case intermediate.  In Ouda photometry
for VSNET charts, I use 9 arcsec aperture, with some explicit comments if
the magnitude is apparently combined one, the pair looking potentially
visualy resolved.

Regards,
Taichi Kato

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