Six (6) Passes of the ISS Observed Overnight
Monday
Night, May
21-22, 2018
On Monday night, May 21-22, 2018,
there would be six (6) passes of the ISS (International Space Station)
visible from Maple Shade, NJ, if weather permitted. This
Bob King online article at Sky & Telescope explains the orbital
geometry of the earth and the ISS that briefly produces the all-night
visibility this time of the year. In addition, the Cygnus cargo
spacecraft, launched Monday morning at 4:44 am, might be visible as it
was catching up to its ISS destination.
The six ISS passes would peak at 8:54 pm, 10:31 pm, 12:08 am, 1:45 am, 3:23 am and finally, 4:59 am EDT. In brief, all passes were seen with unaided eyes for at least a portion of their arcs from my front yard (or the street out front). It was clear for the first two passes, but the final four were at least partially obscured by clouds.
I had little information on where the Cygnus would be with respect to the ISS, so I assumed it would be trailing by an unknown distance. Then I found a pair of photos in the Spaceweather.com gallery showing Cygnus nine (9) minutes behind the ISS as seen from Hungary, about 1:20 UT.
I was groping in the dark so to speak on the first four passes looking for Cygnus (unsuccessfully), but on the fifth pass peaking at 3:23 am, I noticed that it go about 8° directly below Polaris. I watched with 15x56 binoculars and noted the ISS was directly below Polaris at 3:22 am. I also noted that the field was framed by utility wires above and below, and tree branches on the right, so I knew where to look later on (plus it was relatively clear in that patch of sky). After watching the ISS disappear in clouds towards the east, I returned to my sub-Polaris spot. At 3:27 or 3:28 am (reading my accurately-set wristwatch in the dark), I saw an approximate second magnitude object pass along nearly the same track as the ISS in the 15x56s. It must have been Cygnus, 5 or 6 minutes behind the ISS.
By time the final pass of the night occurred, it seemed pretty cloudy in brightening twilight, so I feared I would not catch the ISS. Bright Mars was out just before the pass, but vanished in the clouds by time the pass occurred. I could not find Saturn with unaided eyes, but I could see it's distinctive elongated shape in the 15x56s. At 5 am, the bright ISS passed about a binocular field (4.5°) directly below Saturn. I watched and waited until 5:07 am, but never saw a hint of Cygnus. Either I simply missed it, or more likely, it was too faint in the somewhat cloudy, twilight sky.
Nevertheless, it was a good night since it was the first time I've seen six (6) ISS passes in one night. I had seen five (5) passes several times before, but never six. I also spotted the Cygnus once, so I got to see it briefly during launch and then in orbit later the same day. Not too bad.
Last Update: Monday, May 28, 2018 at 07:44 PM Eastern Time