Orwell Astronomical Society (Ipswich)
Summary of Lunar Occultations for 2011
During 2011, there are over 700 lunar occultations potentially observable from East Anglia, although many involve faint stars. On 17 September, the track of a grazing occultation of a magnitude 5.8 star crosses the region. There are no good planetary occultations visible from the region during 2011.
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.
Table 1 lists occultation events during the year, of stars down to magnitude 6.0, 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.
Date 2011 |
Time (UT) |
D R |
Lunar Phase |
Sun Alt (°) |
Star Alt (°) |
Mag | Star |
14 Jan | 23:11:21 | D | 0.73+ | -58 | 38 | 4.9 | 58 Ari, ζ Ari |
15 Jan | 02:13:54 | D | 0.74+ | -50 | 12 | 5.3 | 61 Ari, τ Ari |
17 Jan | 20:33:44 | D | 0.95+ | -39 | 56 | 4.2 | 1 Gem |
17 Jan | 23:37:10 | D | 0.95+ | -58 | 57 | 5.8 | 3 Gem, PU Gem |
18 Jan | 02:14:03 03:07:37 | D R | 0.96+ | -50 -43 | 37 29 | 3.3 | 7 Gem, η Gem |
16 Feb | 01:35:09 | D | 0.92+ | -47 | 36 | 4.9 | 81 Gem, g Gem |
17 Feb | 20:02:33 | D | 1.00+ | -27 | 29 | 5.1 | 6 Leo, h Leo |
11 Mar 12 Mar | 23:07:17 00:02:48 | D R | 0.39+ | -40 -42 | 17 9 | 4.3 | 69 Tau, υ Tau |
11 Mar 12 Mar | 23:48:55 00:10:00 | D R | 0.39+ | -41 -42 | 12 9 | 5.5 | 72 Tau |
13 Mar | 21:14:52 22:14:31 | D R | 0.59+ | -29 -36 | 49 41 | 3.3 | 7 Gem, η Gem |
18 Mar | 19:17:37 | D | 0.99+ | -12 | 20 | 5.9 | 55 Leo |
18 Mar | 23:05:35 | D | 0.99+ | -37 | 38 | 5.9 | 62 Leo, p3 Leo |
07 Apr | 19:13:08 20:12:34 | D R | 0.15+ | -6 -14 | 33 24 | 4.4 | 37 Tau, A1 Tau |
07 Apr | 19:39:24 20:24:39 | D R | 0.15+ | -10 -16 | 29 22 | 5.9 | 39 Tau, A2 Tau |
15 Apr | 21:14:01 | D | 0.93+ | -19 | 34 | 4.8 | 87 Leo, e Leo |
11 May | 00:06:25 | D | 0.51+ | -20 | 8 | 5.4 | 2 Leo, ω Leo |
11 Aug | 20:50:07 | D | 0.96+ | -11 | 16 | 5.9 | 57 Sgr |
19 Sep 20 Sep | 23:39:09 00:30:48 | D | 0.55- | -37 -36 | 20 28 | 5.0 | 109 Tau, n Tau |
08 Oct | 19:54:57 | D | 0.90+ | -25 | 31 | 5.0 | 63 Aqr, κ Aqr |
09 Oct | 23:27:50 | D | 0.96+ | -44 | 37 | 4.9 | 8 Psc, κ Psc |
24 Oct | 05:19:58 | D | 0.10- | -12 | 16 | 4.8 | 87 Leo, e Leo |
30 Oct | 17:55:44 | D | 0.20+ | -13 | 8 | 5.7 | ZC 2595 |
20 Nov | 02:06:59 02:46:54 | D R | 0.33- | -47 -42 | 10 15 | 5.9 | 62 Leo, p3 Leo |
03 Dec | 16:39:52 | D | 0.62+ | -8 | 34 | 5.7 | 16 Psc |
03 Dec | 23:52:08 | D | 0.64+ | -60 | 12 | 4.9 | 19 Psc, TX Psc |
07 Dec | 21:26:45 | D | 0.93+ | -50 | 56 | 5.8 | 40 Ari |
09 Dec | 19:09:56 | D | 0.99+ | -30 | 35 | 5.7 | ZC 665 |
28 Dec | 16:51:55 | R | 0.17+ | -9 | 25 | 5.1 | 46 Cap, c1 Cap |
Table 1. Occultations of stars of magnitude 6.0 or brighter.
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. During 2011, the Moon occults eta Gem twice and 40 Ari once and grazes it once. There are no other repeated occultations of prominent stars during the year.
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 more than 10 stars. The very large numbers of occultations on 08 April and 07-08 May are associated with the passage of the Moon through star fields in Taurus and Gemini respectively.
Date, No occs | Date, No occs | Date, No occs | Date, No occs |
08 Jan, 11 | 09 Jan, 11 | 07 Feb, 18 | 08 Feb, 11 |
08 Mar, 13 | 09 Mar, 19 | 06 Apr, 12 | 07 Apr, 15 |
08 Apr, 46 | 09 Apr, 18 | 10 Apr, 23 | 06 May, 26 |
07 May, 45 | 08 May, 46 | 30 Oct, 15 | 28 Nov, 18 |
29 Nov, 20 | 27 Dec, 17 | 28 Dec, 20 | 29 Dec, 16 |
Table 2. Nights with more than 10 occultations.
The track of one grazing occultation crosses East Anglia during the year. Table 3 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.
Date 2011 |
Time (UT) |
Limb | Dist OPO (km) |
Limb Profile |
Track Shift (km) |
Google Earth Track |
Google Earth Image |
Lunar Phase |
Sun Alt (°) |
Star Alt (°) |
Star Azi (°) |
Mag | Star |
17 Sep | 02:31 | S | 45 | Profile | 0.7 S | Track | Track | 0.81- | -23 | 56 | 175 | 5.8 | 40 Ari |
Table 3. Grazing lunar occultation.
James Appleton