Comet NEOWISE (C/2020 F3) has been intriguing northern sky watchers all summer and will continue to do so for a bit longer as it travels through the “paws” of Ursa Major. It became glorious as a morning object for amateur astronomers in June, but, after transitioned to the evening sky in July, it has become better appreciated by the general public.
The comet is closest to Earth tonight, July 22, as it makes its evening appearance for the east coast of North America. This will happen at 9:14 pm EDT with the comet 0.692 AU* from the Earth at a predicted 3.3 magnitude and elongation (angle) from the Sun of 37.6°. At this time it will be 0.630 AU from the Sun as it approaches the orbit of Venus (0.723 AU) during its outbound voyage from our star.
*1 AU is the average distance between the centers of the Earth and Sun. It is about 93 million miles / 150 million km.
The official designation “C/2020 F3 (NEOWISE)” arises from the International Astronomical Union Comet Designation System. It tells us the following about the object.
- “C“: non-periodic comet
(Periodic comets have a return period of fewer than 200 years or have at least two observed passages near the Sun.)
- “2020“: discovered in the year 2020
- “F“: discovered in the last half of “March”
(The half-month-letter system uses: “A” = 1st half of January, “B” = 2nd half of January, “C” = 1st half of February, and so-on, but skipping the letter “I”. )
- “3“: the third comet discovered for the half-month
- “NEOWISE“: the name of the discoverer
- “C“: non-periodic comet
To put it all in words, the comet was discovered on 27 March 2020 by the near-Earth Orbit (NEO) mission of the Wide-field Infrared Survey Explorer (WISE) space telescope — thus “NEOWISE”. Calculations indicate that the comet was last in the vicinity of the Sun 4400 years ago. But the next visitation will be 6700 years hence due to changes in its orbit. When it does return, it will carry the periodic comet “P” designation and be assigned the next sequential number in the list of periodic comets.
Al Nagler’s night vision images of the comet in the morning sky (above and below) are amazing in that they were made using ridiculously short 1/8″ exposures on an ordinary Samsung Galaxy J3 smartphone! The first part of the imaging train was conventional: a Tele Vue-76 APO refractor and 67mm Plössl (Tele Vue 55mm and Tele Vue 67mm Converter for 55mm Plössl) at 9x power. On the back-end, a TNVC, Inc PVS-14 L3 Gen3 Un-Filmed White Phosphor night vision monocular was attached to the Plossl and a Tele Vue FoneMate carrying a Samsung Galaxy J3 smartphone was attached to the PVS-14 eyepieces. The image intensifying effect of the PVS-14 allowed the phone to use a short exposure without the need for tracking or imagine stacking!
David Nagler captured the comet in the evening sky using a similar night vision setup. This time the Tele Vue-NP101is APO refractor was used as the imaging scope. The longer focal length and faster optics of this scope caught more of the tail of the comet. Below is a single photo at only 1/6″ exposure on a smartphone.
Comet NEOWISE lightcurve estimates show the comet fading to 5th magnitude by the first week in August. This means it’ll be a naked-eye evening object for dark sites and a binocular target for suburban sites for the next two weeks. After that, barring any outbursts, it’ll be a binocular and then a telescopic target for the rest of the summer.