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Thread: Comet Offpoint Test, August 8, 2018

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    Default Comet Offpoint Test, August 8, 2018

    Tomorrow morning, from 1430-1505 UTC (10:30-11:05 ET), SDO will perform a comet offprint test maneuver. This is only a test, there is no comet that will be visible. However, it has been almost 6 years since we performed such a maneuver and its good to keep in practice. We only get a day or two notice when a Kreutz sun-grazing comet might be visible. This test allows us to put the instructions in a easy to access location for the next comet.
    The Sun will appear to shift to the left during the test. That means it is useful for Kreutz comets in July and August, when the comets appear to come from the right and pass across the face of the Sun. Some science data, such as magnetograms and Dopplergrams, will not be produced while the Sun is shifted from the center of the images.
    When a sun-grazing comet arrives, we will be ready to go comet watching!


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    Default Re: Comet Offpoint Test, August 8, 2018

    Three Bright Comets of 2018


    Discovered by Michael Giacobini in December 1900 at the Nice observatory, this comet caused some confusion when Ernst Zinner unknowingly observed its return 6.5 years later. The comet’s orbital period was thought to be 6.8 years up until that point.

    Giacobini-Zinner’s return in 2018 is a promising one as it passes the Earth at a distance of 0.39 au. In June, 2018, 21p will be observable from modest sized telescopes sitting in the constellation of Cygnus with a brightness of magnitude 11. It will then brighten rapidly through July and August by which time the nucleus may reach naked eye visibility. Rising in the late evenings, 21p remains well placed for observation for most of the summer.

    On the night of 03 September, the comet will lie just over 1 degree from bright star Capella in Auriga making it much easier to locate. The comet reaches closest approach on the night 10/11 September, 2018 after which it rises after midnight. Current predictions peak at magnitude 6, so only just within the naked eye threshold. Through the summer months, comet 21p passes within close visual proximity to quite few deep sky objects during its journey through Cygnus, Camelopardalis, Auriga and Monoceros.


    Despite the name, this comet was discovered by Jerome Coggia at the Marseilles
    Observatory in January 1867, but the name was awarded to E J M Stephan, the Observatory Director as he first calculated the position with accuracy. This comet has an orbital period of 38 years defined as a Halley-type comet hence why it was last observed in 1980/1.

    Perihelion occurs on 26 August, 2018 by which time it should become sufficiently bright enough for backyard telescopes. On the night of 08/09 November, Comet 38p will lie very close to deep sky object NGC 2392 (The Eskimo Nebula) separated by just 8 arcmins, a good photographic opportunity. The comet will remain well placed in the evening skies for the remainder of the year and on in to 2019 when it becomes almost circumpolar in the constellation of Lynx.

    According to NASA’s JPL orbit program, the point at which the Earth is closest to the comet is not actually until January 2019 as the Earth ‘catches up’ with the comet during it’s orbit around the Sun. How bright the icy rock will be will depend on how it reacts to its perihelion passage.


    Comet 46P/Wirtanen is a small short-period comet with an orbital period of 5.4 years. Discovered by Carl A. Wirtanen in 1948 at the Lick Observatory, California, USA. The comet reaches perihelion on 12 December, 2018 and is expected to reach magnitude 3, well within naked eye visibility. This would make it the brightest comet since C/2011 L4 (PANSTARRS) reached a similar magnitude during the twilight hours in April 2013. 46P will be well placed in December residing in Taurus. The ice rock will then pass between the Pleiades and Hyades star clusters just before closest approach where it will reach a distance of 0.078 AU (11.6m kilometers) from the Earth on 18 December. Given the relatively close approach to the Earth, the nucleus of Wirtanen should appear reasonably large in the sky.


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