Orwell Astronomical Society (Ipswich)

Summary of Lunar Occultations for 2019

More about occultations.

Introduction

During 2019, there are almost 600 lunar occultations potentially observable from East Anglia, although many involve faint stars. The tracks of eight grazing occultations cross the region during the year. No lunar occultations of planets are 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 brighter than magnitude 6.0, where circumstances are favourable. The 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 brighter than magnitude 6.0.
 

Occultations During Lunar Eclipse, 21 January 2019

There is a lunar eclipse on 21 January. Weather permitting, the entire event will be visible from the UK. Table 2 lists contact times (from the BAA Handbook):
 

Table 2. Contact times for lunar eclipse.
 

With the glare from the Moon reduced during the eclipse, many more occultations than usual can be visible. In fact, predictions show 17 total occultations plus two grazes, the track of one of which passes within 1 km of Orwell Park Observatory! (See below for details.)

Nights With Many Occultation Events

During the year, the Moon traverses some rich star fields. When this happens, many occultations can occur during a short period. Table 3 lists dates throughout the year when the Moon occults 10 or more stars. (Figures for early morning events are included with those of the previous evening, if any.) The occultations on 21 January occur during a total lunar eclipse, when stars fainter than usual can be seen. The large numbers of occultations during early May are associated with the passage of the Moon through the rich star fields of Taurus, Gemini and Cancer.
 

Table 3. Nights with 10 or more occultations.
 

Grazing Occultations

The tracks of eight grazing occultations cross East Anglia during the year. 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 the closest point on the track, on land. Column five links to a plot of the lunar limb profile visible either (a) from longitude 1.25° E (WGS84) on the track, if this is on land or, if it is not, (b) from the most easterly point on the track on land. 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 the track. (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.
 

Note:

1. There are two grazes on the morning of 01 January, separated by approximately 40 minutes. The tracks run approximately parallel and 5 km apart over East Anglia, providing an opportunity to observe both during a single observing trip!
2. The graze on the night of 21 January occurs during the final stages of a total lunar eclipse. The graze track passes only 1 km from Orwell Park Observatory.
3. There are two grazes within two days in mid-October (19^th and 21^st).

James Appleton

Original: Newsletter January 2019
Updated: 26 March 2023