Solar Eclipse Prime Page

Annular Solar Eclipse of -1685 Jul 20 (1686 Jul 20 BCE)

Fred Espenak

Introduction

The Annular Solar Eclipse of -1685 Jul 20 (1686 Jul 20 BCE) is visible from the geographic regions shown on the map to the right. Click on the map to enlarge it. For an explanation of the features appearing in the map, see Key to Solar Eclipse Maps.

The instant of greatest eclipse takes place on -1685 Jul 20 at 06:32:08 TD (19:40:59 UT1). This is 1.1 days after the Moon reaches apogee. During the eclipse, the Sun is in the constellation Leo. The synodic month in which the eclipse takes place has a Brown Lunation Number of -44618.

The eclipse belongs to Saros 9 and is number 50 of 74 eclipses in the series. All eclipses in this series occur at the Moon’s ascending node. The Moon moves southward with respect to the node with each succeeding eclipse in the series and gamma decreases.

The solar eclipse of -1685 Jul 20 is a relatively long annular eclipse with a duration at greatest eclipse of 07m48s. It has an eclipse magnitude of 0.9349.

The annular solar eclipse of -1685 Jul 20 is followed two weeks later by a partial lunar eclipse on -1685 Aug 03.

These eclipses all take place during a single eclipse season.

The eclipse predictions are given in both Terrestrial Dynamical Time (TD) and Universal Time (UT1). The parameter ΔT is used to convert between these two times (i.e., UT1 = TD - ΔT). ΔT has a value of 39069.8 seconds for this eclipse. The uncertainty in ΔT is 2513.1 seconds corresponding to a standard error in longitude of the eclipse path of ± 10.50°.

The following links provide maps and data for the eclipse.

Orthographic Map: Annular Solar Eclipse of -1685 Jul 20 - global map of eclipse visibility
Google Map: Annular Solar Eclipse of -1685 Jul 20 - interactive map of the eclipse path
Path Table: Annular Solar Eclipse of -1685 Jul 20 - coordinates of the central line and path limits
Circumstances Table: Annular Solar Eclipse of -1685 Jul 20 - eclipse times for hundreds of cities
Saros 9 Table - data for all eclipses in the Saros series

The tables below contain detailed predictions and additional information on the Annular Solar Eclipse of -1685 Jul 20 .

Eclipse Data: Annular Solar Eclipse of -1685 Jul 20

Eclipse Characteristics
Parameter	Value
Eclipse Magnitude	0.93489
Eclipse Obscuration	0.87402
Gamma	-0.85662

Conjunction Times
Event	Calendar Date and Time	Julian Date
Greatest Eclipse	-1685 Jul 20 at 06:32:08.5 TD (19:40:58.6 UT1)	1105811.320123
Ecliptic Conjunction	-1685 Jul 20 at 06:21:59.3 TD (19:30:49.5 UT1)	1105811.313072
Equatorial Conjunction	-1685 Jul 20 at 06:30:18.8 TD (19:39:08.9 UT1)	1105811.318853

Geocentric Coordinates of Sun and Moon
-1685 Jul 20 at 06:32:08.5 TD (19:40:58.6 UT1)
Coordinate	Sun	Moon
Right Ascension	06h46m25.7s	06h46m29.3s
Declination	+23°27'16.3"	+22°41'08.8"
Semi-Diameter	15'51.4"	14'42.8"
Eq. Hor. Parallax	08.7"	0°54'00.0"

Geocentric Libration of Moon
Angle	Value
l	-0.1°
b	1.0°
c	6.5°

Prediction Paramaters
Paramater	Value
Ephemerides	JPL DE406
ΔT	39069.8 s
k (penumbra)	0.2725076
k (umbra)	0.2722810
Saros Series	9 (50/74)

Explanation of Solar Eclipse Data Tables

Penumbral Shadow Contacts and Extremes: Annular Solar Eclipse of -1685 Jul 20

Contacts of Penumbral Shadow with Earth
Contact Event	Contact	Time TD	Time UT1	Latitude	Longitude
First External Contact	P1	03:56:26.1	17:05:16.3	31°10.7'S	151°36.8'W
Last External Contact	P4	09:07:50.6	22:16:40.7	29°21.0'S	078°48.2'W

Extreme Northern and Southern Path Limits of Penumbra
Contact Event	Contact	Time TD	Time UT1	Latitude	Longitude
North Extreme Path Limit 1	N1	04:52:41.7	18:01:31.9	17°04.2'S	173°14.8'W
South Extreme Path Limit 1	S1	08:11:35.7	21:20:25.8	15°11.4'S	057°23.4'W

Explanation of Penumbral Shadow Contacts and Extremes Tables

Umbral Shadow Contacts and Extremes: Annular Solar Eclipse of -1685 Jul 20

Contacts of Umbral Shadow with Earth
Contact Event	Contact	Time TD	Time UT1	Latitude	Longitude
First External Contact	U1	05:26:33.8	18:35:23.9	51°21.3'S	156°29.9'W
First Internal Contact	U2	05:36:31.9	18:45:22.1	54°27.4'S	154°27.6'W
Last Internal Contact	U3	07:27:46.8	20:36:36.9	52°55.8'S	074°43.4'W
Last External Contact	U4	07:37:43.8	20:46:34.0	49°45.3'S	072°59.6'W

Extreme Northern and Southern Path Limits of Umbra
Contact Event	Contact	Time TD	Time UT1	Latitude	Longitude
North Extreme Path Limit 1	N1	05:27:41.2	18:36:31.3	51°05.6'S	157°07.5'W
South Extreme Path Limit 1	S1	05:35:33.0	18:44:23.2	54°40.4'S	153°51.7'W
North Extreme Path Limit 2	N2	07:36:36.6	20:45:26.7	49°29.1'S	072°23.5'W
South Extreme Path Limit 2	S2	07:28:45.6	20:37:35.7	53°09.2'S	075°17.7'W

Explanation of Umbral Shadow Contacts and Extremes Tables

Central Line Extremes and Duration: Annular Solar Eclipse of -1685 Jul 20

Extreme Limits of the Central Line
Contact Event	Contact	Time TD	Time UT1	Latitude	Longitude
Extreme Central Line Limit 1	C1	05:31:23.7	18:40:13.9	52°50.8'S	155°38.3'W
Extreme Central Line Limit 2	C2	07:32:54.4	20:41:44.6	51°16.7'S	073°42.8'W

Explanation of Central Line Extremes Table

Greatest Eclipse and Greatest Duration
Event	Time TD	Time UT1	Latitude	Longitude	Sun Altitude	Sun Azimuth	Path Width	Central Duration
Greatest Eclipse	06:32:08.5	19:40:58.6	35°45.9'S	082°05.1'E	30.8°	358.8°	472.3 km	07m47.78s
Greatest Duration	06:32:13.0	19:41:03.1	35°45.8'S	114°39.2'W	30.8°	358.8°	472.3 km	07m47.78s

Explanation of Greatest Eclipse and Greatest Duration

Polynomial Besselian Elements: Annular Solar Eclipse of -1685 Jul 20

Polynomial Besselian Elements
-1685 Jul 20 at 07:00:00.0 TD (=t0)
n	x	y	d	l1	l2	μ
0	0.25000	-0.85229	23.4551	0.56765	0.02138	285.9653
1	0.50527	0.00898	-0.0033	-0.00003	-0.00003	14.9985
2	-0.00000	-0.00012	-0.0000	-0.00001	-0.00001	0.0000
3	-0.00001	-0.00000	-	-	-	-

Tan ƒ1	0.0046363
Tan ƒ2	0.0046132

At time t1 (decimal hours), each besselian element is evaluated by:

x = x0 + x1*t + x2*t² + x3*t³ (or x = Σ [xn*tⁿ]; n = 0 to 3)

where: t = t1 - t0 (decimal hours) and t0 = 7.000

Explanation of Polynomial Besselian Elements

Links for the Annular Solar Eclipse of -1685 Jul 20 (1686 Jul 20 BCE)

Orthographic Map: Annular Solar Eclipse of -1685 Jul 20 - global map of eclipse visibility
Google Map: Annular Solar Eclipse of -1685 Jul 20 - interactive map of the eclipse path
Path Table: Annular Solar Eclipse of -1685 Jul 20 - coordinates of the central line and path limits
Circumstances Table: Annular Solar Eclipse of -1685 Jul 20 - eclipse times for hundreds of cities
Saros 9 Table - data for all eclipses in the Saros series
Annular Solar Eclipse of -1685 Jul 20 - Google search for links to this eclipse

Links to Additional Solar Eclipse Information

Home - home page of EclipseWise with predictions for both solar and lunar eclipses

Solar Eclipses - primary page for solar eclipse predictions
Solar Eclipse Links - detailed directory of links

Six Millennium Catalog of Solar Eclipses - covers the years -2999 to +3000 (3000 BCE to 3000 CE)
Saros Catalog of Solar Eclipses - covers Saros series -30 through 190
World Atlas of Solar Eclipse Maps - index page
Solar Eclipse Search Engine - search for solar eclipses from -1999 to +3000
Javascript Solar Eclipse Explorer - calculate all solar eclipses visible from a city

Thousand Year Canon of Solar Eclipses 1501 to 2500 - link to the publication

MrEclipse.com - eclipse resources and tips on photography
Solar Eclipses for Beginners - a primer on solar eclipse basics
MrEclipse Photo Index - an index of solar eclipse photographs

Calendar

The Gregorian calendar (also called the Western calendar) is internationally the most widely used civil calendar. It is named for Pope Gregory XIII, who introduced it in 1582. On this website, the Gregorian calendar is used for all calendar dates from 1582 Oct 15 onwards. Before that date, the Julian calendar is used. For more information on this topic, see Calendar Dates.

The Julian calendar does not include the year 0. Thus the year 1 BCE is followed by the year 1 CE (See: BCE/CE Dating Conventions). This is awkward for arithmetic calculations. Years in this catalog are numbered astronomically and include the year 0. Historians should note there is a difference of one year between astronomical dates and BCE dates. Thus, the astronomical year 0 corresponds to 1 BCE, and astronomical year -1 corresponds to 2 BCE, etc..

Eclipse Predictions

Predictions for the Annular Solar Eclipse of -1685 Jul 20 were generated using the JPL DE406 solar and lunar ephemerides. The lunar coordinates were calculated with respect to the Moon's Center of Mass. The predictions are given in both Terrestrial Dynamical Time (TD) and Universal Time (UT1). The parameter ΔT is used to convert between these two times (i.e., UT1 = TD - ΔT). ΔT has a value of 39069.8 seconds for this eclipse. The uncertainty in ΔT is 2513.1 seconds corresponding to a standard error in longitude of the eclipse path of ± 10.50°.

Acknowledgments

Some of the content on this website is based on the book Thousand Year Canon of Solar Eclipses 1501 to 2500. All eclipse calculations are by Fred Espenak, and he assumes full responsibility for their accuracy.

Permission is granted to reproduce eclipse data when accompanied by a link to this page and an acknowledgment:

"Eclipse Predictions by Fred Espenak, www.EclipseWise.com"

The use of diagrams and maps is permitted provided that they are NOT altered (except for re-sizing) and the embedded credit line is NOT removed or covered.