Orwell Astronomical Society (Ipswich)

Summary of Lunar Occultations for 1996

More about occultations.

Introduction

During 1996, there are approximately 490 lunar occultations potentially observable from East Anglia, although many involve faint stars. One grazing occultation of a star and an occultation of Venus are also visible from the region during the year.

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

Table 1 lists occultation events during the year, of stars of magnitude 4.0 or brighter, where the circumstances are favourable. These events should be readily visible in small telescopes or binoculars.

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 of magnitude 4.0 or brighter.
 

Occultations of Double Stars

Occultations of double stars are interesting to observe because the disappearance can occur in two "steps", with a brief intermediate period of reduced intensity. During 1996, there are forty-eight disappearance events involving double stars. Table 2 lists disappearance circumstances of all double stars of magnitude 6.0 or brighter throughout the year. The columns have the same interpretation as those of table 1. Note that 115 Tauri is occulted twice during the year.
 

Table 2. Occultations of double stars of magnitude 6.0 or brighter.
 

Disappearance Events With A Young Moon

Disappearance events of faint stars with a young Moon represent a challenge for observers with large telescopes. During 1996, there are three disappearance events for which the following criteria hold: Sun 10° or more below horizon; star 10° or more above horizon; lunar phase at most 10%. (A rather arbitrary set of selection criteria!) Table 3 summarises the circumstances. The columns have the same interpretation as those of table 1.
 

Table 3. Disappearance events with a young Moon.
 

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 4 lists all evenings throughout the year when the Moon occults more than five stars.
 

Table 4. Nights with more than five occultations.
 

Occultation of Venus

Venus is occulted during 1996. Table 5 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 event occurs during the daytime and will require a telescope to be observed. The occultation will be seen as a graze from Southern Shetland.
 

Table 5. Occultation of Venus.
 

Grazing Occultation

The track of one grazing occultation crosses East Anglia during the year. Table 6 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 6. Grazing lunar occultation.
 

James Appleton

Original: Newsletter January 1996
Updated: 26 March 2023