Orwell Astronomical Society (Ipswich)

Summary of Lunar Occultations for 2006

More about occultations.

Introduction

During 2006, there are approximately 560 lunar occultations potentially observable from East Anglia, although many involve faint stars. There are no good grazing occultations or planetary occultations 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 down to magnitude 5.5, 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 5.5 or brighter.

Note that during the period 02:55–05:30 UT on 04 December, the Moon passes through the Pleiades. Although the Moon is nearly full, making observing conditions less than ideal, providing skies are clear, this sequence of occultations should be spectacular to observe and well worth staying up for!

Occultation Seasons

The Moon’s orbit is defined by a range of periodicities, both short and long term. The short term periodicities mean that the Moon’s path through the sky follows a pattern whereby it almost repeats itself every month. The longer term periodicities gradually shift the orbit so that no particular pattern of approximate repetition can last more than a few years. This results in so called "occultation seasons", lasting for months or years, during which particular stars are repeatedly occulted, or repeatedly not occulted. The effect is most pronounced for the four first magnitude stars that the Moon can occult, namely Aldebaran, Spica, Antares and Regulus. We are currently in an occultation season lasting until 2007 when none of these stars are occulted

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 of the nights in table 2 are associated with the Moon’s passage through rich star fields from east Taurus to central Gemini.
 

Table 2. Nights with 10 or more occultations.
 

James Appleton

Original: Newsletter January 2006
Updated: 26 March 2023