Treasurer Shirley McKeown 0428 488 269

Secretary Fay Neil 6231 0851

Committee Mike Dower 0419 280 944

Peter Enzerink 6251 7484

Ross Gould 6278 4146

Paul Floyd 6292 4670

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 .