
2001 Ephemeris
CAS ORGANISERS
– 2000/2001
Executive and Committee Members
President Andrew
White 6281 1872
Senior Vice-President Karen
Brown 6287 3399
Vice-President Geoff
Spencer 6291 9084
Secretary Fay
Neil 6231 0851
Committee Mike
Dower 0419
280 944
Peter
Enzerink 6251 7484
Ross
Gould 6278 4146
Lucy
Merlino 6255 3525
Tom Hayes 6254 2596
CAS Organisers
Webmaster Peter
Enzerink 6251
7484
Schools Night Coordinator John Morland 6282
5381
Membership Officer John
Howard 6248
0552
Journal Editors Albert
Brakel 6241
3895
Ross
Gould 6278
4146
Public Officer Andrew
White 6281
1872
Librarian Lucy
Merlino 6255
3525
Dome Coordinator Mike
Dower 0419 280
944
Equipment Officer John
Morland 6282
5381
Lighting Project Coordinator John Howard 6248
0552
Graze Coordinator Dave
Herald 6231
9214
Guest Speaker Coordinator Kim Rawlings 6258
8564
Observation Officer Albert
Brakel 6241
3895
RAPT Team Leader Brian
Crook 6231
8269
Historian Michael
Nelmes 6258
8564
A
list of contacts for information on specialist topics appears in the
November
2000 edition of Southern Cross.
Foreword
ephemeris
n., pl. ephemerides. A table showing the positions of a heavenly body on
a number of dates in an orderly sequence [from the Greek: diary, calendar,
record]
When I was studying, I bought “Practical
Astronomy with your Calculator”
by Peter Duffett-Smith. (It was the predecessor of the popular “Practical
Astronomy with your Personal Computer”). This was crammed full of theories and algorithms for calculating
orbits and predicting planetary movements, eclipses, etc. all using your H.P.
calculator. While this was great fun and an excellent way to learn the theory,
it was also very time consuming and mistakes were not uncommon - not
particularly “practical” if you’re planning a night’s
viewing. It does however give me great insight into the efforts required to
produce astronomical ephemerides – especially one as extensive as this.
It was only a comparatively short time ago (remember the days before
computers?) that a work such as this was compiled from the labours of teams of
mathematicians toiling over hot slide rules and log tables.
Dave Herald has spent the last few months compiling
this work with a computer rather than a slide rule and the result is, I
believe, one of the most extensive amateur publications available in this
country – and it’s yours, just for being a CAS member!

It is said that “an organisation is simply
the sum of all its members”.
If Dave is typical of the CAS membership, then the society is capable of
pretty much anything! Use this ephemeris, use the wonderful Mt Stromlo and
society facilities and most importantly enjoy the sky in 2001, confident that
you know exactly where and when events will be occurring.
Andrew White
President
Canberra Astronomical Society
EPHEMERIS
of the
CANBERRA ASTRONOMICAL SOCIETY Inc
For 2001
TABLE OF CONTENTS
CAS
Organisers.............................i
Foreword..................................ii
Table of
Contents........................iii
Explanatory Notes.........................iv
Your
notes..............................viii
Calendar...................................1
Sidereal Time, Julian Day
Numbers..........2
Solar transit and
nutation.................2
Diary of Astronomical
Phenomena............3
Deep Sky site location
maps................6
Rise & Set Times of the major
planets......8
Phases of the
Moon.........................9
Lunar
Eclipses............................10
Solar
Eclipses............................11
Moonrise..................................12
Moonset...................................13
Physical ephemeris of the
Moon............14
Apparent ephemeris of the
Sun.............16
Physical ephemeris of the
Sun.............17
Mercury...................................18
Venus.....................................19
Mars......................................20
Jupiter...................................22
Saturn....................................25
Uranus....................................27
Neptune...................................28
Pluto.....................................29
Jupiter’s
satellites......................30
Lunar occultations for
Canberra...........33
Grazing occultations near
Canberra........42
Asteroidal
Occultations...................44
EXPLANATORY
NOTES
Times
used in this ephemeris
For
the proper use of this ephemeris it is important to understand the time scales
used. The tables listed in the ephemeris are given on one of three different
time scales;
(i)
Local time e.g. rise/set
times
(ii)
Universal Time (UT), and
(iii)
Ephemeris Time. Unless otherwise stated, the
ephemerides are given in Ephemeris Time.
Ephemeris
Time differs from Universal Time by a small amount, this being caused by the
long term slowing down of the earth’s rotation. For 1991 the difference was 58 secs., with ET being ahead of
UT. For most practical purposes,
this difference can be ignored; where it is likely to be significant (eclipses,
occultations, and Jupiter’s satellites), the predictions have included
the correction to Universal Time.
Local Time differs from Universal
Time, for Canberra being 10 hours ahead (or 11 hours if Summer Time is in
effect). NO PREDICTIONS GIVEN
IN LOCAL TIME ARE CORRECTED FOR SUMMER TIME.
If Summer Time is in effect, ADD 1 hour to the predicted Local Time i.e.
0 hours UT corresponds to 10 am Local Standard Time, 11am local Summer Time,
and 12 hours UT corresponds to 10 pm Local Standard Time to 11 pm Summer Time.
Conversions to and from local
time are as follows:
UT/ET AEST AEDT
07:00 h 5:00 PM 6:00 PM
08:00 h 6:00 PM 7:00 PM
09:00 h 7:00 PM 8:00 PM
10:00 h 8:00 PM 9:00 PM
11:00 h 9:00 PM 10:00 PM
12:00 h 10:00 PM 11:00 PM
13:00 h 11:00 PM 12:00 midnight
14:00 h 12:00 midnight 1:00 AM
15:00 h 1:00 AM 2:00 AM
16:00 h 2:00 AM 3:00 AM
17:00 h 3:00 AM 4:00 AM
18:00 h 4:00 AM 5:00 AM
19:00 h 5:00 AM 6:00 AM
20:00 h 6:00 AM 7:00 AM
21:00 h 7:00 AM 8:00 AM
22:00 h 8:00 AM 9:00 AM
1 Julian Day Number (JD).
The Julian Day Number is a
convenient method of comparing different dates. It is a contiguous count of days, commencing on Jan 1, 4713
BC. Because the day was considered
to start at noon (rather than midnight) prior to about 1920, the JD at 0hrs UT
is half a day.
2 Sidereal Time.
The value listed in the
ephemeris is for 0hrs UT. For most
practical purposes, it gives the Right Ascension which is on the meridian at
midnight.
3 Solar Transit.
The value listed is for the
longitude of Canberra with the time in Eastern Standard Time. At the listed time the Sun will be on
the meridian and hence, due north.
4 Solar &
Lunar Eclipses.
The predictions of solar
eclipse include corrections for changes in the site position from that
given. The corrections are
obtained by multiplying the coefficients in longitude and latitude by the
change in longitude (measured to the East) and latitude (measured to the North)
in minutes of arc, and the coefficient in altitude by the change in altitude in
metres. The value obtained is the
correction to the time in seconds, or multiply by 10-6 for the
correction to Delta. Delta is a
measure of the minimum distance of the observer to the axis of the eclipse
shadow axis, in Earth radii.
5 Diary of Astronomical Phenomena.
This table provides a listing
of conjunctions and other interesting phenomena, as seen from the Earth’s
centre. If an eclipse or a lunar
occultation is possible somewhere on the Earth, the event is appropriately
marked.
Some phenomena are difficult
to compute precisely as the variation of the relevant quantity is very small
over the period of a day or so.
For example, at perihelion the change in distance of the Earth from
perihelion to 1 day later is only about 0.000002 astronomical units. Under these circumstances, the time
given in the diary may differ from that published in ‘authoritative’
publications.
6 Rise and Set Times.
These are computed for the
longitude of Canberra with times given in Eastern Standard Time on a 24 hour
clock. No correction for Summer
Time (daylight saving) is included - add 1 hour when Summer Time is in effect.
7 Ephemeris of the
Moon.
The quantities tabulated here
are: the libration in longitude
and latitude (l,b), the position angle of the lunar north pole (Axis), the
lunar Colongitude of the Sun (Coln) - effectively the longitude of the terminator
for the rising Sun, the lunar latitude of the Sun (Lat), and the percent
illumination of the Moon (%ill).
8 Physical Ephemeris of the Sun.
The quantities tabulated here
are: The position angle of the
Solar north pole (Po), the Heliographic latitude of the Earth (Bo), and the
Heliographic longitude of the Earth (Lo).
9 Planetary Ephemerides.
The positions of the Sun and
the planets has been computed for the Equinox of 2000 so that the positions are
directly comparable with star charts drawn to the 2000 equinox.
The quantities tabulated are:
Right Ascension and
Declination
S.D. The
equatorial semidiameter in arc secs.
Elong The
solar elongation in degrees East or West
limb The
position angle of the midpoint of the bright limb.
I The Sun-Planet-Earth
angle ie the solar elongation of the Earth as seen from the planet.
%ill The
percentage illumination of the planet.
Mag The visual magnitude of
the planet.
Additionally, for Mars,
Jupiter and Saturn, the longitude of the central meridian is given for 0hrs
ET., with a motion table to easily obtain the value at the desired time. For Jupiter, System I applies between
the equatorial belts, whilst System II applies outside the two equatorial
belts.
10 Satellites
of Jupiter.
The predictions are based on Sampson’s theory, and differences of up to 3 minutes may be expected for some phenomena. The times refer to the mid-time of the event; all events are gradual, occurring over several minutes. The satellite involved is identified in Roman numerals; the other symbols are: Ec - Eclipse, Oc - occultation, Tr - Transit of the satellite, Sh - Transit of the satellite’s Shadow, D - Disappear, R - Reappear, I - Ingress, E - Egress.
11 Lunar
occultation predictions
The predictions of lunar
occultations are calculated for a site in southern Canberra and corrections for
the lunar limb, including the corrections to the Watts charts determined by Morrison
& Appleby
MNRAS
(1981) 196, 1013-1020, are applied.
The predicted information is
as follows:
Time The universal time, in hours, mins and secs.
P The
type of event (phase):
D disappearance
d - star less than 1 mag brighter than
predicted visibility limit.
R reappearance
r - star less than 1 mag brighter than predicted visibility
limit.
Gr grazing occultation at site. At mid-occultation, or closest approach, the star is less than 4" from the limb of the Moon (either above or below).
gr - star less than 1 mag brighter than predicted visibility
limit.
Star No the star identification number, with the catalogue
indicated as follows:
nnnn ZC
catalogue no.
nnnnn or nnnnnn SAO catalogue number
Xnnnnn USNO
XZ catalogue no.
Q nnnn USNO
Q catalogue no.
Gnnnnnnnn the
Hubble Guide Star Catalogue number (note that this continues through the double
star and spectral type fields.)
D the
double star code. These appear in the table in lower case. The following definitions apply:
A Listed by Aiken or Burnham
B Close double, with third star nearby with separate
XZ entry
C Listed by Innes, Couteau, or other visual
observers
D Primary of double, secondary has separate XZ entry
E Secondary of double, primary has separate XZ entry
F Following component
H Triple: J or U or V, and M
I
O, with secondary either J,
U, or V (third star's data referred to secondary)
J One-line spectroscopic binary, separation probably
<".01
K U or V, but duplicity doubtful
L Triple: J or U, and V; or all V; or all J
M Mean position of close pair
N North component
O Orbital elements available
P Preceding component
Q Triple; J or U or V, and O
R Triple; O and O
S South component
T Triple, V, and A or C; or all A and/or C
U Separation <".01 (usually a double-line
spectroscopic binary)
V Separation >".01 but not visual
W Triple; J or U, and A or C
X Probably a close double, but not certain
Y Triple; K or X, and A or C
Z Triple; O, and A or C or V or X or L
Visual observers will usually
not notice the duplicity of stars with codes J or U.
Sp the
star's spectral type
Mag . the
star's magnitude
%ill. the percent illumination of
the Moon. If followed by a +, values are for a waxing Moon; - for a waning Moon
and e for illumination during a lunar eclipse.
Elon. the elongation of the Moon from the Sun, in
degrees. During a lunar eclipse, this gives the percent distance of the star
from the centre of the umbral shadow, and is followed by 'U'
Sun Alt the altitude of the Sun, but only if it is
greater than -12 deg.
Moon Alt the altitude of the Moon
Moon Az the azimuth of the Moon
CA Cusp Angle - the angle
of the event around the limb of the Moon, measured from the nearest cusp. -'ve
values indicate a bright limb event. The cusps are usually N (north) or S
(south), but near full moon can be E (East) or W (west).
If a lunar eclipse is in progress, CA gives is the % distance from the centre of the umbra, and is followed by a 'U'. Values up to 103% are possible.
PA Position Angle - the
angle of the event around the limb of the Moon, measured from true north
VA . Vertex Angle.
WA Watts Angle - the angle
of the event around the limb of the Moon, measured eastward from the Moon's
north pole. Essential for reappearance, as it locates the event with reference
to lunar features. To use, mark a map of the Moon around the circumference at
10 deg intervals, starting at the north pole. Mare Crisium is at about 300 deg. This provides the Watts
angle scale.
Libn L the
libration of the Moon in longitude, as seen from the site at the time of the
event
Libn B the libration of the Moon in latitude;
A coefficient for
correcting the prediction for changes in site location. The units are seconds
of time per minutes of arc. The correction to the prediction for a change in
site, in seconds of time, is found by multiplying A by the change in site
longitude (in minutes of arc, +'ve to the East) from the prediction site.
B same as for A, but for changes in latitude
(+'ve to the north).
RV .