[vsnet-chat 5934] Re: [AAVSO-DIS] Reporting observations: Multi-letter codes

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Re: [AAVSO-DIS] Reporting observations: Multi-letter codes

Arne,

   I have explained almost everything in a reply to Berto's message.
I presume that even you don't dare to refer to standard V-filtered
observation of extremely red objects with a different notation, even if
the effective wavelength is far from that of the V band.  Think of an
object emitting only Halpha.  The effective wavelength is then around
655 nm, pretty close to that of Rc.  But we don't refer to these magnitude
as Rc.  This is because "V band" is so defined to denote any convoluted
quantity of V-passband and any spectrum.  The same is true for other
passbands.  Any variety of CCD passband is not an exception -- it is
simply not a standard passband, but is a real passband.

>    Here I disagree as a matter of principle and reality.  If you are
> so concerned as to need the full spectral response of the CCD system
> and the star in question, then you should be observing filtered or
> be doing spectroscopy (and be taking the atmospheric transmission
> into account).  A crude adjustment onto the standard system
> as per CR and CV is about all that unfiltered observers should consider.
> *Not* indicating such a zeropoint means the reported magnitudes can be on
> any system and nearly useless.

   I mean that the required system is a "function" of a CCD (and minor
contribution from instumental and atmospheric effect).  So if one
use a specific CCD, one doesn't need to use different symbols.  One doesn't
need to occasionally introduce "CI" for very red objects (this is what
I read from Berto's original posting).

> I haven't seen "CU" used commonly, so you would have to convince me
> that confusion is possible.  I can't help it if people do not use
> a commonly accepted notation when submitting observations; you have
> to educate them.  That is not a reason to reject "CR" and "CV".

   You seem to tend to speak without evidence.  The notation "CU" can be
found in many places, the best examples being Tonny Vaunmunster's cataclysmic
variable circulars.  You may find other examples only if you have ever
tried to search for them.  I have (today) just received a report with
a system "CV".  How can one discern whether this notation was used to
refer to "unfiltered CCD observation reduced on V-band system" or
"CCD V-band observation", without asking to the observer?  Or we should
silently regard them as "unfiltered CCD observation reduced on V-band system"
regardless of the original intention of the observer?  This is already
an evident source of confusion!  Leading people like you must be more
aware of the consequence of an intriduction of a new concept; it is you
who need to educate observers [or possibly you need a re-education for
photometry? -- even an excellent practical photometrist may not be
neccesarily an expert in theoretical background], but not the database
managers such as AAVSO or VSNET.  For me, the introduction of "CCD V"
by the AAVSO instead of simply "V" is another source of confusion;
some people may regard "CV" and an abbreviated form of "CCD V".

Regards,
Taichi Kato

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