Observation of April 13, 1997
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Begin: 20h 30m UT
End: 22h 30m
Ls = 104, diam = 13.0 arcsec
Drawing: 21h 00m, CM 46; 21h 45m, CM 56; 22h 10m, CM 63.
Semi-apo refractor of Osservatorio di Torino, 420 mm f/16.7, 412 X. Seeing
(Antoniadi) II, good transparency.
Notes:
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Very good seeing, the disk of the planet is full of complex details, very
hard to fix them in the drawing! I had some difficulties: also positions
could not be very reliable.
NPC is probably irregular in shape and albedo, with a possible small bright spot in the preceding part as shown in the sketch. The following part of the disk seems to be covered by some haze, diffusing inside the disk over the region of Solis Lacus, showing low contrast. A tentative boundary of the brighter haze is drawn dotted on the second drawing.
At 21h 45m UT a tiny, brown dot appears near the limb: Ascraeus Lacus, or better: Mons. It is a surprise to me, but its presence is nearly obvious. The level of contrast in comparison to the background is close to that of a galilean satellite's shadow on Jupiter seen with a small telescope. But the biggest surprise arrives at 22.22 UT: other two dots are visible, Pavonis and Arsia ! Now and then they seem to form a faint dark segment on the planet, but they are generally easy to separate. The last one is very close to the terminator.
Paolo Tanga
Mars Program Coordinator
Sezione Pianeti - Unione Astrofili Italiani