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               25 Birch Street, Cambridge, MA 02138 USA
           BITNET:  aavso@cfa8     SPAN:  nssdca::cfa8::aavso
               Tel. 617-354-0484       FAX 617-354-0665

              AAVSO ALERT NOTICE 170 (April 21, 1993)

1721-23  NOVA OPHIUCHI 1993

We have been informed by Paul J. Camilleri (Cobram, Victoria, Australia) and 
the Central Bureau for Astronomical Telegrams (IAU Circular 5765) of the 
photographic discovery of a nova by Paul Camilleri on April 14.54 UT at
photovisual magnitude 9.5.  Robert H. McNaught (Anglo-Australian Observatory)
confirmed the presence of the nova, and provided the following precise
position (1950) measured by him on his film taken using the Uppsala Southern 
Schmidt camera at Siding Spring:

        R.A. = 17h 22m 04.41s      Decl. = -23 degrees 08' 32.2"     (1950)

Camilleri's photographic discovery of this nova was made using T-Max patrol
films taken with an 85mm camera lens.  The following observations of N Oph 93 
have been reported (IAU Circulars 5765, 5766, 5769):

April  1.77 UT  [12      Camilleri (photovisual)
      14.54       9.5    Camilleri, discovery (photovisual)
      16.68       9.5    Camilleri (photovisual)
      17.50       9.5    P.F. Williams, Heathcote, NSW, Australia (visual)
      17.52       9.5    Camilleri (visual)
      18.49       9.66 V A.C. Gilmore, Mt. John University Observatory, 
                             New Zealand (photoelectric)
      19.06       9.71 V F. van Wyk, South African Astronomical Observatory 
      19.38       9.6    R. Royer, Lakewood, CA (visual)

Please use the accompanying AAVSO chart to observe N Oph 93 and report your
observations to AAVSO Headquarters.  Indicate the comparison stars used when
reporting observations, and as the nova fades use the letter sequence of 
fainter comparison stars (fainter than 9.6) until we issue a "d" scale chart 
(in preparation) with faint magnitudes.

Congratulations to Paul on his latest (ninth) nova discovery!

0946+69 SUPERNOVA IN NGC 3031 (M81)

This bright supernova, discovered on March 28.86 UT (see AAVSO Alert Notice 
169) at visual magnitude 11.8, brightened to magnitude 10.5 +/- .5 by March 
30, slowly started to fade, reaching magnitude 11.7 +/- .5 by April 4, and 
slowly started to brighten again, reaching magnitude 10.9 +/- .3 by mid-April.
The response to observe this bright supernova has been most enthusiastic from 
observers worldwide.  Regrettably, the scatter in the estimates from observers
is quite significant.  This scatter is probably due to the inhomogeneity of 
the comparison star magnitudes on the charts being used by observers.  There 
are at least these four charts is use:

1. AAVSO preliminary chart 0947+69.  The sequence on this chart came from 
the SAO Catalog and visual estimates by active AAVSO supernova searcher T. 
Fetterman.  There may be zero point problems and inconsistencies in this 

2. Thompson-Bryan chart.  Some magnitudes are photoelectric and some have been 
transferred from the AAVSO preliminary chart.  There are two versions of the 
Thompson-Bryan chart.  Regrettably, some comparison star magnitudes on the 
earlier version, which we distributed with AAVSO Alert Notice 169, are 
slightly different from the later version published by Cambridge University 

3.  Guide Star Catalog chart.  Magnitudes independently obtained by the Space
Telescope Science Institute.  For some stars these magnitudes are quite 
different from the photoelectric (V) magnitudes.

4.  "The Astronomer" chart.  Prepared and distributed by Guy Hurst, with 
selected photoelectric (V) magnitudes and AAVSO visual magnitudes from the
Thompson-Bryan chart.

In the accompanying AAVSO chart of NGC 3031, we have revised the magnitude 
sequence that was distributed with AAVSO Alert Notice 169.  We have adopted 
photoelectric magnitudes reported in the astronomical literature and on the 
Thompson-Bryan chart.  We have replaced with a letter sequence the AAVSO 
visual estimates from the chart distributed with AAVSO Alert Notice 169.  We 
have requested that the astronomical community obtain homogeneous 
photoelectric photometry of this field; to date no new photoelectric 
measurements of comparison stars have been reported.  

We request all observers monitoring this bright supernova to specify what
comparison stars they are using for each estimate when they report their
observations to the AAVSO.  Please indicate from where the sequence came, 
i.e., AAVSO Alert Notice 169 or AAVSO Alert Notice 170, or any other source.  
Specifying the comparison stars and indicating the sequence source are 
extremely important, because as soon as we have a homogeneous comparison star 
sequence for all the stars observers have been using, we will revise the 
reported magnitudes.  The cooperation of all observers will be greatly 

Please continue to observe SN 3031 and report your observations to AAVSO 
Headquarters as it slowly fades.

1810-00 FG SERPENTIS (AS 296)

We have been requested to monitor the interesting symbiotic star FG Ser in 
order to have good coverage of its forthcoming predicted eclipse.  With AAVSO 
Alert Notice 167 we distributed to our observers a Royal Astronomical Society 
of New Zealand chart for FG Ser with a letter comparison star sequence.  
Accompanying is a chart recently prepared by Charles Scovil.  It contains 
photoelectric comparison star magnitudes distributed in RASNZ Variable Star 
Section Chart Series 23, and CCD comparison star magnitudes made by J. 
Morgan (University of Washington) and provided by G. Wallerstein (University 
of Washington).  The two comparison star sequences complement each other.

Please report your observations using these sequences.  If you have already
reported observations using the letter sequence distributed with AAVSO Alert
Notice 167, please convert your letter estimates to magnitudes and re-submit 
them to AAVSO Headquarters.  Be sure to indicate that they are re-submissions.
Your converting your letter estimates and re-submitting them will help us 
greatly in processing your observations.  Please monitor this interesting star
as closely as you can in the coming months and report your observations with 
your monthly reports.

Thank you very much for your observing efforts and contributions, and for 
your enthusiastic response to special requests from astronomers and to 
discoveries of novae and supernovae.

Clear Skies and Good Observing,

Janet A. Mattei

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484