Orwell Astronomical Society (Ipswich)

Summary of Lunar Occultations for 1997

More about occultations.

Introduction

During 1997, there are approximately 550 lunar occultations potentially observable from East Anglia, although many involve faint stars. There are three grazing occultations of stars and an occultation of Saturn also visible from the region.

This article summarises the circumstances of the best occultations during the year. It provides details for the location of Orwell Park Observatory; differences will in general be negligible for locations throughout East Anglia.

Occultations of Bright Stars

The first two columns of the table list the date and time (UT) of the occultation. Column three specifies the phenomenon: "D" denotes a disappearance and "R" a reappearance. The table lists circumstances of D and/or R as dictated by the visibility of each phenomenon (determined by altitude, lunar phase, etc). Column four details the lunar phase (positive waxing and negative waning). Columns five and six give the altitude of the Sun and the star, both in degrees. (A negative solar altitude means that the Sun is below the horizon.) Columns seven and eight provide the star's magnitude and catalogue number.
 

Table 1. Occultations of stars brighter than magnitude 5.0.
 

Nights With Many Occultation Events

During the year, the Moon traverses some rich star fields. When this happens, a large number of occultations can occur during a single evening. Table 2 lists all evenings throughout the year when the Moon occults 10 or more stars; many are associated with the Moon’s passage through rich star fields in Taurus.
 

Table 2. Nights with 10 or more occultations.
 

Occultation of Saturn

Saturn is occulted during 1997. Table 3 provides details; timings refer to the centre of the planetary disk. The interpretation of the columns in the table is the same as that of table 1 (with the obvious difference that the data refers to a planet rather than a star). The occultation will be visible as a northern limb graze from the Faeroe Isles and as a southern limb graze from North Africa. This is the last lunar occultation of a planet which will be visible from East Anglia until February 2002, so it is well worth making the effort to observe if weather conditions permit.
 

Table 3. Occultation of Saturn.
 

Grazing Occultations

The tracks of three grazing occultations cross East Anglia during the year, unusually, within four days of one another. Table 4 summarises the circumstances. Columns one and two give the date and time of the graze and column three specifies the lunar limb involved. Column four indicates the distance between Orwell Park Observatory and point X on the track, on land, where the distance between the two is least; column five links to a plot of the lunar limb profile visible from X. Column six specifies a north or south displacement of the observer's position, relative to the track, based upon inspection of the limb profile, to maximise the chances of witnessing multiple disappearance and reappearance events. Column seven links to an on-line Google Earth plot of the track and column eight links to an off-line image of it. (The plot and image illustrate the nominal track, with no displacement applied.) Column nine details the lunar phase (positive for waxing, negative for waning) and column 10 the altitude of the Sun (a negative solar altitude means that the Sun is below the horizon). Columns 11 and 12 provide the horizontal co-ordinates of the star (azimuth in the order N→E→S→W). Columns 13 and 14 specify the star and its magnitude.
 

Table 4. Grazing lunar occultations.
 

James Appleton

Original: Newsletter January 1997
Updated: 26 March 2023