Friday, February 10, 2017

Friday Night's Dim Penumbral Lunar Eclipse w/ Web-Cast

Lunar eclipse chart close-2017Feb11.png
This graphic shows how the Moon travels through the Earth's Penumbral Shadow during the
Penumbral (partial) Lunar Eclipse of 2017 February 10 to 11. The central gray area (analogous
to a "donut-hole") represents the Umbral (darker) Shadow, while the Penumbral (lighter) Shadow
would be represented by the circle comprising the rest of the "donut."
(Graphic Source: , By SockPuppetForTomruen at English Wikipedia - Own work, Public Domain, )

By Glenn A. Walsh
Reporting for SpaceWatchtower

The first eclipse of 2017, during the Full Moon of February, will be a Penumbral (partial) Lunar Eclipse, or Eclipse of the Moon, which may be dimly visible Friday to Saturday, 2017 February 10 to 11 throughout most of the world, except extreme western Alaska, extreme eastern Asia, Australia, New Zealand and most of the Pacific Ocean. An Internet web-cast of the event will be available for areas where this eclipse cannot be seen, or for areas where inclement weather precludes viewing.

Any Lunar Eclipse or Eclipse of the Moon, whether Total, Partial, or Penumbral, is the type of eclipse which is safe to look at with the naked-eyes, binoculars, and telescopes.

During an Eclipse of the Moon, the Earth's solar shadow shines on part or all of the Moon, always at the time of a Full Moon (when the Moon, Earth, and Sun, in that order, lie in a straight line). As sunlight strikes our planet, the Earth actually casts two shadows into Outer Space: the main and darker, cone-shaped Umbral Shadow, along with the secondary and dimmer Penumbral Shadow which surrounds the Umbral Shadow.

In a Total Lunar Eclipse, the Earth's Umbral Shadow completely envelops the Moon, after the Moon passes through the Penumbral Shadow. In the case of a Partial Eclipse of the Moon, only part of the Moon is covered by the Umbral Shadow, but again, the Moon does also pass through the Penumbral Shadow.

During a Penumbral Eclipse of the Moon, only the dimmer Penumbral Shadow covers part or all of the Moon. In the case of the February 10 to 11 eclipse, a Penumbral (partial) Lunar Eclipse will occur, as the Moon does not completely enter the Earth's Penumbral Shadow.

A Penumbral Eclipse of the Moon is much dimmer than a Partial Eclipse of the Moon or a Total Eclipse of the Moon. The Moon is not dimmer, but the shading of the Moon is much lighter than seen during other eclipses, making the Moon appear almost as bright as normal.

The shading of the Moon during a Penumbral Eclipse is extremely subtle, and not everyone may be able to tell when the eclipse is occurring by observation. So, although some people may notice that the Moon is slightly dimmer than usual, other people may not notice the difference. However, despite not being a complete Penumbral Eclipse, this particular eclipse does traverse the darkest areas of the Penumbral Shadow, so it may be a little easier to notice than other Penumbral Eclipses.

Technically, the entire eclipse lasts four and one-third hours. However, the human eye cannot perceive the entire eclipse, due its dim nature. Likely, one or two hours of the eclipse, centered around the time of greatest eclipse, may be visible to most people.

As this eclipse occurs when the Moon is rising in the Western Hemisphere (on the evening of February 10), it is best seen in the eastern sections of North and South America; the farther west the observer, the more the observer will have to contend with evening twilight. Asian viewers have the opposite problem, as they will need to contend with morning twilight (on February 11) as the Moon is about to set. The entire eclipse will be visible to viewers in Europe, Africa, Middle East, Greenland, Iceland, Quebec, New England, and most of Brazil.

To determine when the Moon rises and / or sets in your location, you can enter your locality data on a form of an Internet web page managed by the U.S. Naval Observatory; both Form A (for U.S. Cities and Towns) and Form B (for Locations Worldwide) are on this web page. A link to this web page is located at the end of this blog-post.

               Times of Penumbral (partial) Lunar Eclipse Phases – 2017 February 10 to 11
                        (EST = Eastern Standard Time; UTC = Coordinated Universal Time)

Penumbral Lunar Eclipse Begins:                  Feb. 10, 5:34:16 p.m. EST / 22:34:16 UTC
Ecliptic Conjunction:                                       Feb. 10, 7:32:51.3 p.m. EST / Feb. 11, 0:32:51.3 UTC
Moon Phase - Full Moon:                               Feb. 10, 7:33 p.m. EST / Feb. 11, 0:33 UTC
Greatest Penumbral Lunar Eclipse:               Feb. 10, 7:43:52.9 p.m. EST / Feb. 11, 0:43:52.9 UTC
Penumbral Lunar Eclipse Ends:                     Feb. 10, 9:53:26 p.m. EST / Feb. 11, 2:53:26 UTC

Special Note: Although the times given for the beginning and ending of the Penumbral Eclipse are the correct times, it is highly unlikely that the beginning and ending can be viewed visually. On average, a Penumbral Eclipse is only visible a half-hour before until a half-hour after the time of greatest eclipse.

Observations of the exact times when the Penumbral Eclipse is actually first visible, and when the Eclipse is actually no longer visible, would be valuable to Science. For those interested in making such serious observations, a photometer giving the light intensity coming from the Moon would be helpful.

The bright object to the lower left the Moon (during the evening hours of Feb. 10) and above and closer to the Moon (in the morning hours of Feb. 11), during this eclipse, is the Star Regulus, brightest star of the well-known Constellation Leo the Lion and one of the brightest stars in the sky. About 11 hours after the eclipse (February 11, 9:00 a.m. EST / 14:00 UTC) the Moon will occult, or cover-up, Regulus; this occultation is visible in areas where the eclipse was not visible, including Australia and New Zealand.

Eclipses only occur occasionally (usually around four times a year, with two of these being Lunar Eclipses). A Lunar Eclipse or Eclipse of the Moon occurs only a couple times a year, on average, because the Moon's orbit around the Earth is slightly tilted with respect to Earth's orbit around the Sun. For most months of the year, the Moon passes a little above, or a little below, the Earth's shadow (precluding a Lunar Eclipse).

Of course eclipses, like all celestial observations, are weather-permitting. If the weather in your area does not permit direct viewing outdoors of this Penumbral (partial) Eclipse of the Moon, it can be viewed during a special, live web-cast on the Internet, followed by a live web-cast of Comet 45P / Honda-Mrkos-Pajdusakova as the Comet is about to make its closest approach to Earth since 1983. A link to this web-cast is located at the end of this blog-post.

Other eclipses this year include an Annular Solar Eclipse later this month, on February 26. The other Lunar Eclipse in 2017 is a Partial Lunar Eclipse on August 7. And, this year's eclipses culminate in the middle of Summer with the Great American Total Eclipse of the Sun on August 21, which will follow a path across the United States from Oregon to South Carolina!

Most Native Americans in the Northern Hemisphere referred to the February Full Moon as the Snow Moon for obvious reasons--particularly obvious with yesterday's blizzard in the north-eastern United States. Other Native American tribes have called the February Full Moon the Hunger Moon, due to the difficult hunting conditions during the harsh weather of the month.

While the January Full Moon (and for some tribes the December Full Moon) has been known by some tribes as the Wolf Moon, other tribes referred to the February Full Moon as the Wolf Moon. The Full Moon of February has also been known as the Racoon Moon and the Bare-Spots-on-the-Ground Moon.

In the Southern Hemisphere, the February / Mid-Summer Full Moon has been known as the Grain Moon, Sturgeon Moon, Red Moon, Wyrt Moon, Corn Moon, Dog Moon, and Barley Moon.

Once every 19 years, February has no Full Moon. This is due to the fact that February has only 28 days (29 days once every four years during the Leap Year) while the time duration of the Moon's orbit around the Earth is even shorter: 27.32166 days.

U.S. Naval Observatory Web Page --- Rise / Set Times for Moon and Sun:
Link >>>

Slooh Community Observatory --- Live, Internet Web-Cast of Feb. 10 Penumbral Lunar Eclipse - Feb. 10, 5:30 p.m. EST / 22:30 UTC; Followed by Live, Internet Web-Cast of
Comet 45P / Honda-Mrkos-Pajdusakova as the Comet is about to make its closest approach to Earth since 1983 - Feb. 10, 10:30 p.m. EST / Feb. 11, 3:30 UTC:
Link >>>

Internet Links to Additional Information ---

Penumbral (partial) Lunar Eclipse of 2017 Feb. 10 to 11:
Link 1 >>>
Link 2 >>>
Link 3 >>>

Parts of a Shadow: Umbra, Penumbra, Antumbra:
Link >>>

Penumbral Lunar Eclipse: Link >>>

Lunar Eclipse: Link >>>

Eclipse: Link >>>

Star Regulus: Link >>>

Occultation: Link >>>

Related Blog Posts ---

"Dim Penumbral Lunar Eclipse Early Wed. Morning." 2016 March 22.

Link >>>


"Slight Lunar Eclipse Friday Evening." 2013 Oct. 17.

Link >>>

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2017 February 10.

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