NavList:

I see there are some early-risers on this list. Here is the ouput from a little planning tool that has helped me setting my alarm clock over the past few years.

A. Potential observations of Galilean Satellites at Greenwich in October 2002

mm-dd   UT1      sat phen ev  RAsun  RAjup  DECjup     AZ     Hsun    Hjup

10- 1 02:22:56     I  EC  D   12.47   8.98   17.59     80    -31.9    14.2
10- 5 03:18:20    II  EC  D   12.72   9.03   17.42     93    -26.1    24.7
10- 8 04:16:26     I  EC  D   12.90   9.06   17.29    107    -18.5    35.1
10-12 05:52:50    II  EC  D   13.15   9.10   17.13    138     -4.6    49.4
10-15 06:09:56     I  EC  D   13.34   9.13   17.01    147     -2.7    51.9
10-17 00:38:20     I  EC  D   13.45   9.15   16.94     70    -46.2     6.0
10-24 02:31:44     I  EC  D   13.89   9.21   16.70     97    -37.6    26.9
10-30 00:17:56    II  EC  D   14.27   9.25   16.52     75    -51.5     9.3
10-31 04:25:14     I  EC  D   14.35   9.26   16.48    131    -22.9    46.3
 

B. Potential observations of Galilean Satellites at WAS observatory in October 2002

mm-dd   UT1      sat phen ev  RAsun  RAjup  DECjup     AZ     Hsun    Hjup

10- 4 07:54:08   III  EC  D   12.67   9.02   17.45     85    -33.3    21.1
10- 6 09:48:02     I  EC  D   12.80   9.04   17.37    106    -13.2    43.5
10-12 05:52:50    II  EC  D   13.15   9.10   17.13     70    -52.4     3.4
10-15 06:09:56     I  EC  D   13.34   9.13   17.01     75    -51.5     8.3
10-19 08:26:56    II  EC  D   13.59   9.17   16.86     99    -30.9    36.3
10-22 08:03:26     I  EC  D   13.78   9.19   16.76     97    -35.7    33.8
10-26 11:00:56    II  EC  D   14.04   9.22   16.62    155     -3.6    63.5
10-29 09:56:56     I  EC  D   14.23   9.25   16.53    131    -16.1    57.3
 

The above two tables list eclipses of the Galilean satellites that might be observable from the places named in the header. (Greenwich is a place where they once had an important observatory and WAS is theAstronomical Society of Westport, Connecticut, N41/W73, where they still have an observatory.) If you don't live too far from either of these two places, this will give you a rough idea of what you can see. Other places on request, preferably offline.

I have listed only eclipses, because only those are suitable for longitude determination. (But transits are actually more fun to watch.) As it happens, no eclipses for sat III and IV are observable this month from either place, and for the other satellites you can see only their beginnings (D stands for debut) at this time of the year.

This is only a planning tool!! Listed are the mid-times between internal and external contact on entrance into, or exit from, umbra. For detailed timing information on the individual events as well as for entrance/exit into/from penumbra you should consult the IMCCE ephemeris directly. You may see the satellites starting to fade ca. 2 minutes before the time listed in my table. Be at the telescope early and make sure you are looking at the correct satellite.

The table entries should be self explanatory. Times are given as Universal Time. RA stands for right ascension. RAjup and RAsun help understanding the geometry of the situation and why you see certain phenomena and not other ones. The azimuth is that of Jupiter. H denotes altitude. Not knowing anything about an observer's local situation, I chose H= 0d as as a cut-off altitude for both, Jupiter and Sun, although this is highly unrealistic. It depends on your local horizon how high up you need Jupiter and on atmospheric conditions and the quality of your telescope how far down you need the sun. Hjup > 8 and Hsun < -8 normally work well. The entries for 10/12 and 10/15 at Greenwich and the ones for 10/12 and 10/26 here at WAS are questionable.

Have fun.

Herbert Prinz

Credits go to:
IMCCE for the times of satellite phenomena,
USNO for topocentric positions of Jupiter and Sun,
Herbert Prinz for all errors in the above.