[vsnet-chat 2961] (fwd) Re: Tycho,Tycho-2,Hipparcos magnitudes

[Taichi Kato <tkato>]

(fwd) Re: Tycho,Tycho-2,Hipparcos magnitudes

Date: Tue, 23 May 2000 19:55:41 -0700 (MST)
From: Brian Skiff <bas@lowell.edu>
Message-ID: <20002961@hoge.baba.hajime.jp>
To: tkato@kusastro.kyoto-u.ac.jp
Subject: Re: [vsnet-chat 2959] (fwd) Tycho,Tycho-2,Hipparcos magnitudes
Cc: vsnet-chat@kusastro.kyoto-u.ac.jp

     Is there perhaps a confusion here between the "instrumental" Tycho
magnitudes (VT and BT) and magnitudes corrected to the standard system?
Although Hipparcos magnitudes for bright stars have high _precision_,
their _accuracy_ is low, and of course these are also not on any standard
system.  The Tycho-1 catalogue was supplied with corrected V and B-V, but
Tycho-2 was not---could this be causing confusion amongst observers?
Certainly the tests that John Greaves and I ran of (corrected) Tycho-2
against standard catalogues showed that Tycho-2 was invariably better
over the entire magnitude range.

\Brian

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