The first study of the local interstellar medium (LISM) toward Puppis-Vela
(1 = 245 degrees to 275 degrees, b = -15 degrees to +5 degrees, d < 200 pc)
is presented in this paper. A study of the locations, sizes, and physical
characteristics of local interstellar gas, i.e."astronephography, is includ
ed, and relies upon the improved distance measurements provided by Hipparco
s parallax measurements. All spectra of more distant sight lines contain ab
sorption features due to intervening local gas, and more distant structures
can only be studied accurately if components due to the LISM have been iso
lated. Towards this end, high-resolution (R <approximate to> 95,000), high
signal-to-noise (S/N similar to 110 to 250) Na I lambda lambda 5889.951, 58
95.924 spectra of 11 nearby stars in the direction of Puppis-Vela have been
obtained with the Coude Echelle Spectrograph on the 1.4 m Coude Auxiliary
Telescope at the European Southern Observatory. Toward Puppis-Vela, absorpt
ion due to the Local Interstellar Cloud (LIC) was not observed, but compone
nts at three distinct velocities were found, and the extent of the local ga
s producing the features was estimated. The three components have the follo
wing locations and velocities: component A-(l approximate to 276 degrees to
298 degrees, b approximate to -5 degrees to +4 degrees), V-hello = +6 to 9 km s(-1) and d similar to 104 pc; component B-(l approximate to 264 degre
es to 276 degrees, b approximate to -7 degrees to + 3 degrees), V-hello = 12 to +15 km s(-1), and d similar to 115 pc; component C-(l approximate to
252 degrees to 271 degrees, b approximate to -8 degrees to -6 degrees), V-
hello = +21 to +23 km s(-1) and d similar to 131 pc. The conclusions regard
ing the ultraviolet spectrum of gamma (2) Vel (l = 263 degrees, b = -8 degr
ees, d = 258 +/- 35 pc) presented by Fitzpatrick & Spitzer were reexamined
in light of this new LISM data, and the ambiguity in their conclusions abou
t several absorption components is resolved. The stars in Puppis-Vela flank
the region of the apparent extension of the Local Bubble (or Cavity) known
as the beta CMa tunnel, and measurements of the Na I column density toward
s the sample stars have been used to modify existing estimates of the exten
t of the tunnel. A compilation of all existing Na I observations of less th
an 200 pc sight lines around the tunnel reveal that low column densities ha
ve been exclusively detected within l approximate to 210 degrees to 250 deg
rees, and b approximate to -21 degrees to -9 degrees. Near the Galactic pla
ne, at latitudes - 10 degrees < b < 0 degrees and d less than or similar to
150 pc, the tunnel is cofined to l < 270<degrees>, a lower longitude than
was previously reported.