Penumbral Lunar Eclipse of 1785 Jul 21

Fred Espenak

Introduction


The Penumbral Lunar Eclipse of 1785 Jul 21 is visible from the geographic regions shown on the map to the right. The diagram above the map depicts the Moon's path with respect to Earth's umbral and penumbral shadows. Click on the figure to enlarge it. For an explanation of the features appearing in the figure, see Key to Lunar Eclipse Figures.

The instant of greatest eclipse takes place on 1785 Jul 21 at 23:45:47 TD (23:45:30 UT1). This is 2.5 days before the Moon reaches perigee. During the eclipse, the Moon is in the constellation Capricornus. The synodic month in which the eclipse takes place has a Brown Lunation Number of -1700.

The eclipse belongs to Saros 106 and is number 67 of 73 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 penumbral lunar eclipse of 1785 Jul 21 is followed two weeks later by a annular solar eclipse on 1785 Aug 05.

Another lunar eclipse occurs one synodic month after the 1785 Jul 21 eclipse. It is the penumbral lunar eclipse of 1785 Aug 20.

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 16.6 seconds for this eclipse.

The following links provide maps and data for the eclipse.

The tables below contain detailed predictions and additional information on the Penumbral Lunar Eclipse of 1785 Jul 21 .


Eclipse Data: Penumbral Lunar Eclipse of 1785 Jul 21

Eclipse Characteristics
Parameter Value
Penumbral Magnitude 0.71345
Umbral Magnitude-0.25672
Gamma-1.16059
Epsilon 1.1521°
Opposition Times
Event Calendar Date & Time Julian Date
Greatest Eclipse 1785 Jul 21 at 23:45:47.0 TD (23:45:30.4 UT1) 2373220.489935
Ecliptic Opposition 1785 Jul 21 at 23:33:52.8 TD (23:33:36.2 UT1) 2373220.481669
Equatorial Opposition 1785 Jul 21 at 23:06:45.6 TD (23:06:29.0 UT1) 2373220.462836
Geocentric Coordinates of Sun and Moon
1785 Jul 21 at 23:45:47.0 TD (23:45:30.4 UT1)
Coordinate Sun Moon
Right Ascension08h06m26.6s20h07m56.2s
Declination+20°17'30.1"-21°23'23.2"
Semi-Diameter 15'44.8" 16'13.8"
Eq. Hor. Parallax 08.7" 0°59'34.0"
Geocentric Libration of Moon
Angle Value
l -3.9°
b 1.5°
c -10.7°
Earth's Shadows
Parameter Value
Penumbral Radius 1.2676°
Umbral Radius 0.7427°
Prediction Paramaters
Paramater Value
Ephemerides JPL DE406
ΔT 16.6 s
Shadow Rule Danjon
Shadow Enlargement 1.010
Saros Series 106 (67/73)

Explanation of Lunar Eclipse Data Tables

Eclipse Contacts: Penumbral Lunar Eclipse of 1785 Jul 21

Lunar Eclipse Contacts
Eclipse Event Contact Time
TD
Time
UT1
Zenith Latitude Zenith Longitude Position Angle Axis Distance
Penumbral BeginsP121:56:42.021:56:25.421°42.6'S031°43.0'E 203.9° 1.5372°
Greatest EclipseGreatest23:45:47.023:45:30.421°23.4'S005°29.5'E 162.4° 1.1521°
Penumbral EndsP401:34:59.401:34:42.821°03.6'S020°46.0'W 120.9° 1.5389°
Eclipse Durations
Eclipse Phase Duration
Penumbral (P4 - P1)03h38m17.4s

Explanation of Lunar Eclipse Contacts Table

Polynomial Besselian Elements: Penumbral Lunar Eclipse of 1785 Jul 21

Polynomial Besselian Elements
1785 Jul 21 at 00:00:00.0 TD (=t0)
n x y d f1 f2 f3
0 0.47422 -1.05831 0.3541 1.26764 0.74277 0.27053
1 0.53457 0.16925 -0.0001 0.00038 0.00038 0.00010
2 0.00015 0.00026 -0.0000 -0.00000 -0.00000 -0.00000
3 -0.00001 -0.00000 - - - -

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 = 0.000

Explanation of Besselian Elements

Links for the Penumbral Lunar Eclipse of 1785 Jul 21

Links to Additional Lunar Eclipse Information

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 Penumbral Lunar Eclipse of 1785 Jul 21 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 16.6 seconds for this eclipse.

Acknowledgments

Some of the content on this web site is based on the book Thousand Year Canon of Lunar 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.