| Partial eclipse | |||||||||||||
 The Moon's hourly motion shown right to left | |||||||||||||
| Date | October 28, 1939 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Gamma | −0.4581 | ||||||||||||
| Magnitude | 0.9876 | ||||||||||||
| Saros cycle | 135 (19 of 71) | ||||||||||||
| Partiality | 203 minutes, 22 seconds | ||||||||||||
| Penumbral | 346 minutes, 5 seconds | ||||||||||||
| |||||||||||||
A partiallunar eclipse occurred at the Moon’sdescending node of orbit on Saturday, October 28, 1939,[1] with an umbralmagnitude of 0.9876. A lunar eclipse occurs when theMoon moves into theEarth's shadow, causing the Moon to be darkened. A partial lunar eclipse occurs when one part of the Moon is in the Earth's umbra, while the other part is in the Earth's penumbra. Unlike asolar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on thenight side of Earth. Occurring about 5.3 days afterapogee (on October 23, 1939, at 0:05 UTC), the Moon's apparent diameter was smaller.[2]
This lunar eclipse was the last of analmost tetrad, with the others being onMay 14, 1938 (total);November 7, 1938 (total); andMay 3, 1939 (total).
This was the last partial lunar eclipse of the first set of partial eclipses inLunar Saros 135 as well as the largest partial lunar eclipse of the20th century.
The eclipse was completely visible overNorth America and westernSouth America, seen rising overnortheast Asia and easternAustralia and setting over eastern South America,west andcentral Africa, andEurope.[3]
 |
Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.[4]
| Parameter | Value |
|---|---|
| Penumbral Magnitude | 2.04769 |
| Umbral Magnitude | 0.98764 |
| Gamma | −0.45812 |
| Sun Right Ascension | 14h06m46.1s |
| Sun Declination | -12°50'04.8" |
| Sun Semi-Diameter | 16'05.9" |
| Sun Equatorial Horizontal Parallax | 08.9" |
| Moon Right Ascension | 02h07m11.5s |
| Moon Declination | +12°25'18.8" |
| Moon Semi-Diameter | 15'11.2" |
| Moon Equatorial Horizontal Parallax | 0°55'44.2" |
| ΔT | 24.4 s |
This eclipse is part of aneclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by afortnight.
| October 12 Ascending node (new moon) | October 28 Descending node (full moon) |
|---|---|
 | |
| Total solar eclipse Solar Saros 123 | Partial lunar eclipse Lunar Saros 135 |
This eclipse is a member of asemester series. An eclipse in a semester series of lunar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternatingnodes of the Moon's orbit.[5]
The penumbral lunar eclipse onMarch 23, 1940 occurs in the next lunar year eclipse set.
| Lunar eclipse series sets from 1937 to 1940 | ||||||||
|---|---|---|---|---|---|---|---|---|
| Ascending node | Descending node | |||||||
| Saros | Date Viewing | Type Chart | Gamma | Saros | Date Viewing | Type Chart | Gamma | |
| 110 | 1937 May 25 | Penumbral | −1.1582 | 115 | 1937 Nov 18 | Partial | 0.9421 | |
| 120 | 1938 May 14 | Total | −0.3994 | 125 | 1938 Nov 07 | Total | 0.2739 | |
| 130 | 1939 May 03 | Total | 0.3693 | 135 | 1939 Oct 28 | Partial | −0.4581 | |
| 140 | 1940 Apr 22 | Penumbral | 1.0741 | 145 | 1940 Oct 16 | Penumbral | −1.1925 | |
This eclipse is a part ofSaros series 135, repeating every 18 years, 11 days, and containing 71 events. The series started with a penumbral lunar eclipse on April 13, 1615. It contains partial eclipses from July 20, 1777 throughOctober 28, 1939; total eclipses fromNovember 7, 1957 through July 6, 2354; and a second set of partial eclipses from July 16, 2372 through September 19, 2480. The series ends at member 71 as a penumbral eclipse on May 18, 2877.
The longest duration of totality will be produced by member 37 at 106 minutes, 13 seconds on May 12, 2264. All eclipses in this series occur at the Moon’sdescending node of orbit.[6]
| Greatest | First | |||
|---|---|---|---|---|
| The greatest eclipse of the series will occur on2264 May 12, lasting 106 minutes, 13 seconds.[7] | Penumbral | Partial | Total | Central |
| 1615 Apr 13 | 1777 Jul 20 | 1957 Nov 07 | 2174 Mar 18 | |
| Last | ||||
| Central | Total | Partial | Penumbral | |
| 2318 Jun 14 | 2354 Jul 06 | 2480 Sep 19 | 2877 May 18 | |
Eclipses are tabulated in three columns; every third eclipse in the same column is oneexeligmos apart, so they all cast shadows over approximately the same parts of the Earth.
| Series members 12–33 occur between 1801 and 2200: | |||||
|---|---|---|---|---|---|
| 12 | 13 | 14 | |||
| 1813 Aug 12 | 1831 Aug 23 | 1849 Sep 02 | |||
| 15 | 16 | 17 | |||
| 1867 Sep 14 | 1885 Sep 24 | 1903 Oct 06 | |||
 |  | ||||
| 18 | 19 | 20 | |||
| 1921 Oct 16 | 1939 Oct 28 | 1957 Nov 07 | |||
 |  | | | |  |
| 21 | 22 | 23 | |||
| 1975 Nov 18 | 1993 Nov 29 | 2011 Dec 10 | |||
 |  |  |  |  |  |
| 24 | 25 | 26 | |||
| 2029 Dec 20 | 2048 Jan 01 | 2066 Jan 11 | |||
 |  |  |  |  |  |
| 27 | 28 | 29 | |||
| 2084 Jan 22 | 2102 Feb 03 | 2120 Feb 14 | |||
 |  | ||||
| 30 | 31 | 32 | |||
| 2138 Feb 24 | 2156 Mar 07 | 2174 Mar 18 | |||
| 33 | |||||
| 2192 Mar 28 | |||||
This eclipse is a part of atritos cycle, repeating at alternating nodes every 135synodic months (≈ 3986.63 days, or 11 years minus 1 month). Their appearance and longitude are irregular due to a lack of synchronization with theanomalistic month (period of perigee), but groupings of 3 tritos cycles (≈ 33 years minus 3 months) come close (≈ 434.044 anomalistic months), so eclipses are similar in these groupings.
| Series members between 1801 and 2200 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1808 Nov 03 (Saros 123) | 1819 Oct 03 (Saros 124) | 1830 Sep 02 (Saros 125) | 1841 Aug 02 (Saros 126) | 1852 Jul 01 (Saros 127) | |||||
| 1863 Jun 01 (Saros 128) | 1874 May 01 (Saros 129) | 1885 Mar 30 (Saros 130) | 1896 Feb 28 (Saros 131) | 1907 Jan 29 (Saros 132) | |||||
 |  | ||||||||
| 1917 Dec 28 (Saros 133) | 1928 Nov 27 (Saros 134) | 1939 Oct 28 (Saros 135) | 1950 Sep 26 (Saros 136) | 1961 Aug 26 (Saros 137) | |||||
 |  |  |  | | |  |  |  |  |
| 1972 Jul 26 (Saros 138) | 1983 Jun 25 (Saros 139) | 1994 May 25 (Saros 140) | 2005 Apr 24 (Saros 141) | 2016 Mar 23 (Saros 142) | |||||
 |  |  |  |  |  |  |  |  |  |
| 2027 Feb 20 (Saros 143) | 2038 Jan 21 (Saros 144) | 2048 Dec 20 (Saros 145) | 2059 Nov 19 (Saros 146) | 2070 Oct 19 (Saros 147) | |||||
 |  |  |  |  |  |  |  |  |  |
| 2081 Sep 18 (Saros 148) | 2092 Aug 17 (Saros 149) | 2103 Jul 19 (Saros 150) | 2114 Jun 18 (Saros 151) | 2125 May 17 (Saros 152) | |||||
| 2136 Apr 16 (Saros 153) | 2169 Jan 13 (Saros 156) | ||||||||
| 2190 Nov 12 (Saros 158) | |||||||||
This eclipse is a part of the long periodinex cycle, repeating at alternating nodes, every 358synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with theanomalistic month (period of perigee). However, groupings of 3 inex cycles (≈ 87 years minus 2 months) comes close (≈ 1,151.02 anomalistic months), so eclipses are similar in these groupings.
| Series members between 1801 and 2200 | |||||
|---|---|---|---|---|---|
| 1824 Jan 16 (Saros 131) | 1852 Dec 26 (Saros 132) | 1881 Dec 05 (Saros 133) | |||
| 1910 Nov 17 (Saros 134) | 1939 Oct 28 (Saros 135) | 1968 Oct 06 (Saros 136) | |||
 |  | | |  |  |
| 1997 Sep 16 (Saros 137) | 2026 Aug 28 (Saros 138) | 2055 Aug 07 (Saros 139) | |||
 |  |  |  |  |  |
| 2084 Jul 17 (Saros 140) | 2113 Jun 29 (Saros 141) | 2142 Jun 08 (Saros 142) | |||
| 2171 May 19 (Saros 143) | 2200 Apr 30 (Saros 144) | ||||
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (ahalf saros).[8] This lunar eclipse is related to two total solar eclipses ofSolar Saros 142.
| October 21, 1930 | November 1, 1948 |
|---|---|
 |  |
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