Return to Home Page
>> 4) Tycho-2 for stars fainter than 8 and brighter than ~9.5. Tycho-
>> magnitudes (transformed to V) suffer for some systematic color -term that
>> makes white and yellow stars to appear with a whiter B-V color (peaking
>> around B-V 0.5 with a difference of 0.06-0.07 mag.) and white and blue stars
>> to appear with a V mag 0.01-0.02 mag. brighter than Johnson's V.
>> In Tycho-1 this effect is less pronounced and thus negligible, but accuracy
>> falls steeper beyond 8th magnitude.
Do you have some plots demonstrating this with respect to primary
standards (specifically the Landolt and Cousins E-region standards)?
What transformation are you using to get Johnson V from VT? Bessell?
The "official" Tycho-consortium transformation is not adequate at the
level you're talking about, and might introduce just the errors you
are noticing.
\Brian
Return to the Powerful Daisaku
vsnet-adm@kusastro.kyoto-u.ac.jp
