Observing Comet NEOWISE

August 2020  :  Craig Cortis

Because of the covid situation and the facts that I don’t get a newspaper and don’t have email, a smartphone or any other means by which to automatically receive any kinds of news alerts, I did not become aware of this bright new comet until around July 13.  I caught a brief mention of the comet on a tv news show and looked it up online the next morning at work.  A printout of an ephemeris enabled me to plot its path on a star atlas.  Saturday night on 7/18 was actually fairly clear at my home location in the southwest corner of Oxford, MA.  The Moon would become New on 7/20.

My neighborhood is about 13 miles south-southwest of the center of Worcester, 2 miles west of I 395 and 5 miles north of the Conn. state line.  Usually there are only 1 or 2 bright lights outdoors within my direct view, but they’re hundreds of feet away to the south and southwest and I can block them out by changing my observing position or using my SUV as a screen.  The sky brightness here has markedly increased over the years but it’s still fairly dark compared to much of this region.  I’m lucky to have a large property that’s fairly secluded, bordered on the north and west by dense woods and big open lawns, on the east and northeast by lawns and trees, and on the south and southwest by my astronomy-friendly  neighbor who has come over with his daughter to observe special sky phenomena several times  with me over the last few years, for which he’s been very appreciative.  No problems with bright lights emanating from his property, thankfully.  My house sits well above the nearby road, which runs parallel to and along the bottom of a high, long, steep embankment forming the eastern border of the property.  Trees line the top edge and slope of the embankment and help to screen headlights along the road below.  A 250 foot-long driveway completes the picture.

I’ve gone into such descriptive detail about my home surroundings because my sense is that many fellow astronomers tend to have at least some interest in knowing the basic observing conditions with which others must contend, particularly with respect to lights and skyglow.  It’s a shame we always have to be so concerned with lights, but it is unavoidable, after all.  Those of you who are new to astronomy are undoubtedly becoming aware of this problem in ways that might not have been noticed by you before.  The proliferation of L.E.D. lights everywhere has only exacerbated the situation.

The position of Comet NEOWISE in UMa on the evening of 7/18 made it form a striking, nearly equilateral triangle with the stars Iota (Talitha) and Kappa UMa, which form the northwestern pair of the “Three Leaps of the Gazelle” pairs.  This pair is separated on the sky by about 1.1 degree, yet is actually the tightest of the three wide pairs comprising the charmingly-named asterism.  Iota UMa is 3.1 magnitude, Kappa is about 3.6 and an impossibly tight double.  Iota also is a double, but with a 9.5 magnitude companion at only 2”  separation, it’s a challenge to split.  The position is RA 08 59.2, Dec. + 48 degrees 02 minutes.  I decided that 9:30 would be the best time to begin observing, as it was a good compromise between the lowering altitude of the comet over the northwest horizon and the remaining twilight.  (Nautical twilight was not to end until 9:34, when astronomical twilight would begin and last until 10:20 or so.)

I started looking with a 10X50 binocular and almost immediately spotted the comet right next to the two stars.  The bright false nucleus did indeed approximate the visual magnitude of Iota UMa and a nice, sharply-defined tail convinced me that this was the best comet I’d seen since Hale-Bopp in 1997.  In fact, its nucleus looked almost stellar.  After a few minutes I set up my 4.12” Astroscan reflector, with a focal length of 442 mm.  I used a 28 mm Plossl eyepiece for a low magnification of just 16 power and an easy, wide field.  The eyepiece had been made by our own Ed Turco, a respected and well-liked senior member of this club.  As an aside to newer members who may not be familiar with him, Ed Turco is among a small, select group of astronomers in Skyscrapers who might be considered master telescope makers and astronomical opticians.  We are fortunate to have him in our ranks.

I did not expect to be able to see NEOWISE naked-eye, despite all the hype and reports of it being easily seen in that way.  Therefore, I satisfied myself with the view through the Astroscan and went back indoors by 9:50.  The next night was cloudy, but both Monday and Tuesday, 7/20 – 7/21, were reasonably clear.  I again used the reflector on Monday and tried a 12mm Kellner at 37 power in addition to the 28mm eyepiece, but the image was degraded.  On Tuesday night I used the 10x50 bino, followed by a 15x70 bino for a very pleasing view.  The comet’s tail seemed to’ve increased in length and its overall brightness had not dimmed since Saturday, 7/18.  NEOWISE was still high enough by 10:00 p.m. on 7/21 to see above a treeline and I stayed out long enough so that the diminishing twilight revealed it easily to the naked eye.  The tail looked to be roughly 5 to 7 degrees long.  

7/25/20 further comet sightings included views at 9:15 - 9:25 and 10:10 using my 15X70 bino and by naked-eye alone at 10:10. The view by naked-eye was dim but discernable; the comet's false nucleus on 7/25 had enlarged and dimmed a bit since 7/21 and its tail had become more wispy and diaphanous, as well as longer. At 10:10 the comet was positioned such that it made a perfect "coathanger" - type triangle with the stars 57 and 55 UMa, mags.5.2 and 4.8. The comet formed the center (or "hook") of this triangle, and was north of the wide pair of stars. The Moon was still one hour and 17 minutes away from setting at 10:10.

 Good luck and best regards to you all – it’s been years since I last  wrote anything for this newsletter.