# August 2016 lunar eclipse

A penumbral lunar eclipse occurred at the Moon’s descending node of orbit on Thursday, August 18, 2016, with an umbral magnitude of −0.9925. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A penumbral lunar eclipse occurs when part or all of the Moon's near side passes into the Earth's penumbra. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. Occurring about 3.4 days before perigee (on August 21, 2016, at 21:20 UTC), the Moon's apparent diameter was larger.
The HM National Almanac Office's online canon of eclipses lists this event as the last eclipse on Saros Series 109, while NASA lists August 8, 1998 as the last eclipse of the series, and has this event missing the shadow.
This eclipse grazed the northern boundary of the Earth's penumbral shadow. The event lasted 33 minutes and 36 seconds, beginning at 9:25 UTC and ending at 9:59. This produced a maximum penumbral magnitude of 0.0166. Eclipses of such small magnitudes are visually imperceptible; a penumbral magnitude of approximately 0.6 is required for even skilled observers to detect.

## Background

The Earth's penumbral shadow is larger than would be expected from simple geometry, a phenomenon first observed by Philippe de La Hire in 1707. The precise amount of enlargement varies over time for reasons which are not fully understood, but likely involve the amount of dust in certain layers of the Earth's atmosphere. Various eclipse almanacs have used different assumptions about the magnitude of this effect, resulting in disagreement about the predicted duration of lunar eclipses or, in the case of penumbral eclipses of very short duration, whether the eclipse will occur at all.
In 1989, NASA published a lunar eclipse almanac that predicted a short penumbral lunar eclipse to occur on 18 August 2016. However, the French almanac Connaissance des Temps used more conservative assumptions about the size of the Earth's shadow and did not predict an eclipse to occur at all. The Bureau des Longitudes in France continued to refine their lunar eclipse models; NASA's 2009 edition of its lunar eclipse almanac was based on their values, which effectively reclassified nine eclipses between 1801 and 2300 as non-events, including the one in August 2016.
Some resources, including the HM Nautical Almanac Office's online canon of eclipses, continued to list the 18 August 2016 event. Despite not appearing in NASA's printed lists of eclipses since the 2009 revision, AccuWeather reported the upcoming eclipse and projected this was the final member of Lunar Saros 109.

## Visibility

The eclipse was completely visible over Australia, North and South America, and Antarctica, seen rising over western Australia and northeast Asia and setting over eastern North and South America.
* Hourly motion shown right to left

## Eclipse season

This eclipse is part of an eclipse 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 a fortnight. The first and last eclipse in this sequence is separated by one synodic month.
Eclipse season of August–September 2016 :
| August 18 Descending node (full moon) | September 1 Ascending node (new moon) | September 16 Descending node (full moon) |
| Penumbral lunar eclipse Lunar Saros 109 | Annular solar eclipse Solar Saros 135 | Penumbral lunar eclipse Lunar Saros 147 |

## Related eclipses
### Eclipses in 2016

* A total solar eclipse on March 9.
* A penumbral lunar eclipse on March 23.
* A penumbral lunar eclipse on August 18.
* An annular solar eclipse on September 1.
* A penumbral lunar eclipse on September 16.

### Metonic

* Followed by: Lunar eclipse of June 5, 2020

### Tzolkinex

* Preceded by: Lunar eclipse of July 7, 2009

### Tritos

* Followed by: Lunar eclipse of July 18, 2027

### Lunar Saros 109

* Preceded by: Lunar eclipse of August 8, 1998

### Inex

* Preceded by: Lunar eclipse of April 14, 1987
* Followed by: Lunar eclipse of March 3, 2045

### Triad

* Followed by: Lunar eclipse of June 20, 2103

### Lunar eclipses of 2016–2020

This eclipse is a member of a semester series. An eclipse in a semester series of lunar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.
The penumbral lunar eclipses on March 23, 2016 and September 16, 2016 occur in the previous lunar year eclipse set, and the penumbral lunar eclipses on June 5, 2020 and November 30, 2020 occur in the next lunar year eclipse set.
Lunar eclipse series sets from 2016 to 2020 :
| Descending node | Descending node | Descending node | Descending node | Ascending node | Ascending node | Ascending node | Ascending node |
| Saros | Date Viewing | Type Chart | Gamma | Saros | Date Viewing | Type Chart | Gamma |
| 109 | 2016 Aug 18 | Penumbral | 1.5641 | 114 | 2017 Feb 11 | Penumbral | −1.0255 |
| 119 | 2017 Aug 07 | Partial | 0.8669 | 124 | 2018 Jan 31 | Total | −0.3014 |
| 129 | 2018 Jul 27 | Total | 0.1168 | 134 | 2019 Jan 21 | Total | 0.3684 |
| 139 | 2019 Jul 16 | Partial | −0.6430 | 144 | 2020 Jan 10 | Penumbral | 1.0727 |
| 149 | 2020 Jul 05 | Penumbral | −1.3639 |

### Saros 109

This eclipse is a part of Saros series 109, repeating every 18 years, 11 days, and containing 71 or 72 events (depending on the source). The series started with a penumbral lunar eclipse on June 27, 736 AD. It contains partial eclipses from September 22, 880 AD through April 16, 1223; total eclipses from April 27, 1241 through October 17, 1529; and a second set of partial eclipses from October 28, 1547 through May 22, 1872. The series ends at member 71 as a penumbral eclipse on August 8, 1998, though some sources count a possible penumbral eclipse on August 18, 2016 as the last eclipse of the series.
The longest duration of totality was produced by member 35 at 99 minutes, 45 seconds on July 1, 1349. All eclipses in this series occur at the Moon’s descending node of orbit.
| Greatest | First | First | First | First |
| The greatest eclipse of the series occurred on 1349 Jul 01, lasting 99 minutes, 45 seconds. | Penumbral | Partial | Total | Central |
| The greatest eclipse of the series occurred on 1349 Jul 01, lasting 99 minutes, 45 seconds. | 736 Jun 27 | 880 Sep 22 | 1241 Apr 27 | 1295 May 30 |
| Last ||||
| The greatest eclipse of the series occurred on 1349 Jul 01, lasting 99 minutes, 45 seconds. | Central | Total | Partial | Penumbral |
| The greatest eclipse of the series occurred on 1349 Jul 01, lasting 99 minutes, 45 seconds. | 1421 Aug 13 | 1529 Oct 17 | 1872 May 22 | 1998 Aug 08 |
Eclipses are tabulated in three columns; every third eclipse in the same column is one exeligmos apart, so they all cast shadows over approximately the same parts of the Earth.
Series members 61–72 occur between 1801 and 2016: :
| 61 | 61 | 62 | 62 | 63 | 63 |
| 1818 Apr 21 | 1818 Apr 21 | 1836 May 01 | 1836 May 01 | 1854 May 12 | 1854 May 12 |
| 64 | 64 | 65 | 65 | 66 | 66 |
| 1872 May 22 | 1872 May 22 | 1890 Jun 03 | 1890 Jun 03 | 1908 Jun 14 | 1908 Jun 14 |
| 67 | 67 | 68 | 68 | 69 | 69 |
| 1926 Jun 25 | 1926 Jun 25 | 1944 Jul 06 | 1944 Jul 06 | 1962 Jul 17 | 1962 Jul 17 |
| 70 | 70 | 71 | 71 | 72 | 72 |
| 1980 Jul 27 | 1980 Jul 27 | 1998 Aug 08 | 1998 Aug 08 | 2016 Aug 18 | 2016 Aug 18 |

### Inex series

This eclipse is a part of the long period inex cycle, repeating at alternating nodes, every 358 synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic 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 :
| 1814 Jan 06 (Saros 102) | 1814 Jan 06 (Saros 102) | 1842 Dec 17 (Saros 103) | 1842 Dec 17 (Saros 103) | | |
| | | 2016 Aug 18 (Saros 109) | 2016 Aug 18 (Saros 109) | | |
| 2074 Jul 08 (Saros 111) | 2074 Jul 08 (Saros 111) | 2103 Jun 20 (Saros 112) | 2103 Jun 20 (Saros 112) | 2132 May 30 (Saros 113) | 2132 May 30 (Saros 113) |
| 2161 May 09 (Saros 114) | 2161 May 09 (Saros 114) | 2190 Apr 20 (Saros 115) | 2190 Apr 20 (Saros 115) |