Summer has finally given way to fall, and in the chill October sky two eclipses are set to occur: a total lunar eclipse at dawn, and a partial solar eclipse at sunset. The planets are also present: Mars and Saturn are visible in the evening twilight, Jupiter rises after midnight, and at month’s end, Mercury appears at daybreak. Venus, on the other hand, is lost in the Sun’s glare.
Two eclipses in a month may seem unusual but in fact, solar and lunar eclipses are related; one never happens without the other. Moreover, they’re not that rare: On average, at least 2 solar and lunar eclipses, either partial or total, take place somewhere on Earth each year. However, what is rare is to see a total solar eclipse twice from the same place on Earth: That only happens about once every 375 years… But before going any further, let’s look at why eclipses happen…
Solar eclipses can only occur during new moon (when the Moon is between the Sun and Earth); lunar eclipses only occur during full moon (when the Earth is between the Sun and Moon). But there’s another condition: The Earth, Moon and Sun must all align. Only during such an alignment can the Moon pass in front of the Sun, or pass through Earth’s shadow. Most of the time that doesn’t happen because the Moon’s orbit is tilted about 5 degrees compared to Earth’s orbit — otherwise there would be eclipses every month. So most of the time the new moon appears either above or below the Sun; and likewise, the full moon passes either above or below Earth’s shadow. But during “eclipse seasons”, which occur every 5.75 months, this alignment does take place; so two times a year there will be a lunar eclipse followed by a solar eclipse, or visa versa.
One more thing… Because Earth’s diameter is about 4 times the diameter of the Moon, its shadow is much larger; so total lunar eclipses are more common than total solar eclipses, and they are visible from anywhere the Moon can be seen. On the other hand, solar eclipses are only visible from specific regions on the Earth’s surface.
During this eclipse season two eclipses will occur — one total lunar, one partial solar — and both will take place close to the horizon as viewed throughout regions of Quebec.
First a lunar eclipse…
On October 8, toward night’s end and at dawn, a total lunar eclipse will unfold — the second in 2014. This eclipse will be visible from Quebec but under frustrating conditions: The initial partial phases start at 5:14 A.M. (EDT) and will be observable against a dark sky; but daylight will encroach just as totality begins, and shortly thereafter throughout most regions of Quebec, one can expect to lose sight of the Moon as it sets on the western horizon. In Montreal for example, mid-eclipse will occur at 6:54; sunrise will be at 7:01; and moonset will take place at 7:07. However, those in western North America will be able to see the entire eclipse unfold, from beginning to end, under a dark sky. None-the-less, any eclipse is worth seeing no matter the circumstances: To make the most of this one, make sure to have an unobstructed view of the western horizon.
Normally, during a total lunar eclipse, one would expect to see the Moon take on a deep, copper red colour — the result of sunlight filtering through Earth’s atmosphere and colouring the Moon, much like a sunset. However, this time around, daylight will reduce contrast making any reddening difficult to see.
One final note: At first glance, one might mistake the initial partial phases for a crescent moon; but a closer look reveals that the curve of the “terminator” (the line separating the lit part from the dark part) is much flatter than it is for monthly lunar phases, and results from the much larger radius of curvature of Earth’s shadow (see accompanying illustration).
…Then a solar eclipse
On October 23, at the end of the afternoon, the second partial solar eclipse of the year will occur and will be visible from certain parts of North America. (The last one took place on April 29 but was only seen from eastern Australia, part of Antarctica and the south-western Indian Ocean.) In Montreal, this eclipse will start at 5:38 P.M. (EDT), just 15 minutes before sunset, as part of the Moon begins to move in front of the solar disk, from right to left. At approximately 5:52, when the Sun touches the west-southwest horizon, the Moon’s silhouette will cover 8% of the solar disk (see accompanying illustration). As a result, the setting Sun will appear to have a “bite” taken out of it. Once again, to make the most out of this eclipse a perfectly clear view of the horizon will be essential. Those in western and northern regions of the continent are favoured, since they’ll get to see 74% of the Sun’s surface hidden by the Moon.
Caution: Special filters are always required to observe the Sun safely through optical instruments. If you're unsure about your observing equipment, the better option is to refrain from watching the eclipse. Seek help and tips from amateur astronomer clubs and societies in your area, and read our page on this very topic.
The planets at a glance
Mars and Saturn spent the latter half of summer, shining in tandem in the evening twilight, among the stars of Libra above the southwest horizon. However, because Mars has a much shorter orbital period than its ringed counterpart, it has since left Saturn behind. The Red Planet quickly moved eastward through Scorpius, and as October begins Mars shines in Ophiuchus: On the 21st, it enters Sagittarius where it will spend the remainder of the month. Due to its rapid eastward movement through the constellations, Mars manages to stay ahead of the Sun, maintaining a more-or-less constant altitude above the same point on the horizon; look for it in the southwest about an hour after sunset. However, Saturn isn’t so fortunate: It continues its inevitable descent toward the horizon and becomes lost in the glow of twilight after mid-month. On the evening of October 28, a waxing crescent Moon will appear about eight degrees above Mars in the fading twilight.
Jupiter rises about 2:30 A.M. in the east-northeast around the beginning of October; it shines among the stars of Cancer until the 15th after which it moves into Leo. As the month progresses, the giant planet appears earlier and earlier: By month’s end it rises before 1:00 A.M. and is well above the southeast horizon by dawn. Jupiter is a remarkable sight through a small telescope: It’s dark cloud bands, and constantly moving Galilean moons, always provide a spectacular show. The waning crescent moon will appear to the right of the giant planet on October 17, and just below it on October 18.
Mercury is lost in the Sun’s glare for the better part of the month: In fact, the elusive planet is at inferior conjunction (between the Sun and Earth) on October 16. However, during the last week of October, Mercury quickly gains both altitude and brightness as it separates from the Sun and begins its best morning apparition of the year. By month’s end Mercury and the Sun will be more than 18 degrees apart, making it relatively easy to spot. Look for the tiny planet in the morning twilight, above the east-southeast horizon, 45 minutes before sunrise: Binoculars will reveal the stars of Virgo shining in the background.