Electronic Telegram No. 3433
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMETS C/2012 F6 (LEMMON) AND C/2011 L4 (PANSTARRS)
     C. Opitom, E. Jehin, J. Manfroid, and M. Gillon, Liege University, report
that they obtained one set of narrowband photometry of the long-period comet
C/2012 F6 on Mar. 3 (when r = 0.84 AU) using the robotic TRAPPIST 0.6-m
telescope at the European Southern Observatory at La Silla, resulting in the
following averaged production rates, in molecules/s (found via a Haser model
with V_p = V_d = 1 km/s):  log Q(OH) = 29.36; log Q(NH) = 27.05; log Q(CN) =
26.96; log Q(C_2) = 27.20; log Q(C_3) = 26.50; and Af[rho](526.0 nm) = 6380 cm
at 10000 km.  The activity of the comet has been rising steeply; Q(CN) has
increased three times since mid-February and five times since mid-January.
Several jets are found to rotate in phase with the gas light curves.
     Two sets of narrowband photometry were also obtained on comet C/2011 L4
on Feb. 8 (when r = 0.86 AU) during twilight and at high airmass, resulting in
the following averaged production rates:  log Q(OH) = 28.60; log Q(NH) =
26.64; log Q(CN) = 26.22; log Q(C_2) = 26.45; log Q(C_3) = 26.02;
Af[rho](526.0 nm) = 12300 cm.  C/2011 L4 is a very dusty comet with respect to
Q(OH), but its composition is typical in C_2 and CN.

     Visual total-magnitude and coma-diameter estimates for C/2012 F6:  2012
Nov. 22.24 UT, 11.3, 2'.5 (J. J. Gonzalez, Cantabria, Spain, 0.20-m reflector);
Dec. 12.69, 9.8, 6' (M. Mattiazzo, Castlemaine, Victoria, Australia, 20-cm
reflector); 2013 Jan. 9.85, 7.8, 9' (K. Yoshimoto, Yamaguchi, Japan, 20x100
binoculars); 24.83, 6.8, 7' (A. Pearce, Nedlands, W. Australia, 0.10-m
reflector); Feb. 2.26, 6.0, 8' (W. Souza, Sao Paulo, Brazil, 7x50 binoculars);
11.51, 5.4, -- (David A. J. Seargent, Cowra, NSW, Australia, naked eye); 16.49,
4.9, -- (Seargent); 19.77, 5.4, -- (S. J. O'Meara, Maun, Botswana, 8x42
binoculars; moonlight); Mar. 2.95, 5.2, 8' (A. Amorim, Florianopolis, Brazil,
10x50 binoculars).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 March 7                     (CBET 3433)              Daniel W. E. Green