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Algol eclipse dates and times for November 2018
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.
Messier 35 - M35 - Open Cluster
M35 is a fantastic open cluster located in the constellation of Gemini. At magnitude +5.2, it's visible to the naked eye under good conditions. Curiously, despite being a naked eye object, it wasn't discovered until 1745-46 by Philippe Loys de Chéseaux and then independently "re-discovered" by John Bevis sometime before 1750. Since the cluster is reasonable close at 2,800 light-years it presents a large apparent diameter of some 28 arc minutes - almost exactly the same as that of the full Moon. Without a doubt, M35 is a magnificent sight in all types of optical instruments.
The constellation Gemini covers a reasonable 514 sq. degrees and is partially located in the rich star fields of the Milky Way. During the winter months, it's positioned high in the sky for Northern Hemisphere observers although less well placed for those located further south. Surprisingly, despite such a prime Milky Way location, M35 is the only Messier object in Gemini. It's located at the western edge of the constellation in a corner of the sky close to the Taurus, Orion and Auriga borders. Finding M35 is quite easy as it's 3.5 degrees northwest of mag. +2.9 star, Mu (μ) Gem.
NGC 869 and NGC 884 - The Double Cluster - Open Clusters
NGC 869 and NGC 884 are two bright open clusters in the constellation of Perseus, that are separated by only half a degree of apparent sky. Together they are commonly known as the "Double Cluster" and form a famous showpiece object, that's easily visible to the naked eye and a wonderful sight in binoculars and telescopes. Both clusters have been known since antiquity and probably pre-historically. Greek astronomer Hipparchus first catalogued them around 130 B.C, with early celestial cartographers naming them as "h Persei" (NGC 869) and "χ Persei" (NGC 884).
The Double Cluster is located in the far northwestern part of Perseus, close to the border with Cassiopeia. With a declination of 57N, it's circumpolar from many northern locations and therefore never sets. To locate the object, draw an imaginary line from Mirfak (α Per - mag +1.8) in a northwesterly direction towards the centre of the "W" of Cassiopeia. The Double Cluster lies just over halfway along this line.
It's listed as number 14 in the Caldwell catalogue.
Finder Chart for NGC 869 and NGC 884 The Double Cluster - pdf format (credit:- freestarcharts)
The Planets this Month - October 2018
Mercury
Mercury is an early evening object during the second half of October from southern and tropical latitudes. The fast moving planet can be seen low above the western horizon just after sunset. During the visibility period its brightness hardly changes at about magnitude -0.2. By month's end, from mid-latitude southern locations, Mercury sets 1 hour and 45 minutes after the Sun. From mid-latitude northern locations, the planet is not so well placed, but might just be spotted very low in the west towards the tail end of the month.
On October 14th, Mercury (mag. -0.3) passes 7 degrees north of much brighter Venus (mag. -4.5) and on October 30th, Mercury passes 3 degrees south of Jupiter (mag. -1.7).
Venus
Venus is an early evening object visible during the first half of the month from southern and equatorial latitudes. However, the planet will move closer to the Sun with each passing day. Observers at mid-latitude northern locations will struggle to spot Venus at all this month.
As previously mentioned on October 14th, Venus and Mercury are located in the same region of sky. Venus reaches inferior conjunction on October 25th.
Orion - Constellation Guide
Orion
Orionis
Ori
The Hunter
Introduction
Orion is a prominent constellation that's one of the brightest and most familiar sights in the night sky. Straddling the celestial equator it can be seen from all locations on Earth. Named after a great hunter in Greek mythology, it contains two first magnitude stars, many other bright stars, a famous belt, spectacular nebulae, some impressive multiple stars and fine open clusters. Its most famous inhabitant, the Orion Nebula, is one of the most spectacular deep sky objects in the sky.
The distinctive pattern of Orion has been used historically and in the modern World extensively. The earliest linking is an ivory carving found in a cave in the Ach valley in Germany, which is estimated to be at least 32,000 years old. In Greek mythology, Orion was a handsome strong hunter, born to Euryale the daughter of King Minos of Crete and Poseidon, the god of the sea. Many myths surround the character particularly involving his death. Various versions exist, but generally Orion brought the wrath of goddess Artemis who sent the scorpion to kill him. The resulting outcome is that the hunter and the scorpion are placed on opposite sides of the sky. When Scorpius rises in the east, Orion is setting in the west.
Messier 45 - M45 - The Pleiades (Open Cluster)
M45, commonly known as the Pleiades or Seven Sisters, is the finest open cluster in the sky. It's a breathtaking site, known since antiquity and easily visible to the naked eye. Located in the large and prominent zodiac constellation of Taurus, this showpiece object is best seen during the Northern Hemisphere Winter and the Southern Hemisphere Summer months.
Finding M45 is easy. The cluster is positioned about 14 degrees northwest of orange giant star Aldebaran (mag. +0.9), the brightest star in Taurus. At first glance with the naked eye, it's obvious that something is special about this small section of sky. On closer inspection, M45 reveals itself to be a beautiful cluster of about half a dozen white stars, covering an area much greater than that of the full Moon. At the heart of the cluster is a set of stars that form a small dipper shape, similar to the brightest stars of Ursa Major. Even under light polluted skies the dipper shape is readily visible. From dark sites, the Pleiades is an outstanding naked eye object. The main stars appear bright and striking, with up to 10 or more visible under ideal conditions.
Algol eclipse dates and times for October 2018
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.
The Planets this Month - September 2018
Mercury
Mercury is a difficult target for observation this month. The innermost planet can be seen low down in eastern twilight during the first week of September, but at best rises only about 45 minutes before the Sun.
Mercury reaches perihelion on September 2nd, when it's positioned 0.307 AU (approx. 45.9 million kilometres or 28.5 million miles) from the Sun. On September 5th, the planet (mag. -1.1) passes a degree north of Regulus (α Leo - mag. +1.4). It then moves towards superior conjunction, which it reaches on September 20th.
Venus
Venus remains a brilliant early evening object from southern and tropical locations throughout September. The unmistakable planet is located in Virgo, and appears as a beacon of light above the western horizon just after sunset. Venus increases in magnitude from -4.6 to -4.8, with its illuminated phase decreasing from 40% to 18%. As the month progresses the planet's apparent diameter increases from 29 to 46 arc seconds.
Algol eclipse dates and times for September 2018
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.