We’ve now gained 40 minutes of evening daylight and 10 minutes in the morning. Can you tell? I noticed the shift yesterday when I was driving home in sunset-pink air around 5 o’clock. Back in mid-December, the sun bid farewell at 4:21 p.m. with twilight well underway by 5. I’m no fan of summer’s long days but a little extra daylight doesn’t hurt. Sure takes the edge off the current cold snap. Cold may be uncomfortable, but polar air masses often bring clear skies. And if you dress warmly 15 minutes of starry skies a night may be all you need to avoid that stuck-inside feeling.
I’ve got an enticement for you. The International Space Station has just returned to the evening sky for a fine series of passes now through mid-February. I caught my first one yesterday evening just after 6:30 p.m. local time and am looking forward to more. The ISS is the brightest of the satellites because it’s enormous. Spanning 356 feet (109 meters) it’s not only as long as a football field but wide enough to include the amphitheater seating.
On occasion, other much smaller satellites will “flare” and momentarily outshine the space station but when it comes to consistent brightness, the ISS is tops. At best it easily outshines Jupiter and almost Venus.
Like many satellites the ISS was launched into an orbit that tracks from west to east across the sky, opposite the motion of the sun, moon and stars. NASA and other space agencies do this to get a free boost from Earth’s west-to-east rotation so they can save on fuel. Earth’s rotation rate varies by latitude. At the poles it’s 0 mph; 736 mph at 45° N and 1,040 mph at the equator. NASA would be nuts to build a spacecraft launch facility in Minneapolis when they can put it in southern Florida and gain an extra 180 mph of free orbital speed. To figure out how fast the planet spins at your home, click here and enter your latitude. Don’t know your latitude? Click here.
The ISS starts low in the west but soon climbs into good view. As it rises higher for an observer it also gets closer to us and brighter. When it passes directly overhead the ship is closest because there’s only about 250 miles (400 km) between you and the station with zero horizontal distance. If you see it off to the north or south, it’s 250 miles and hundreds of miles distant in the horizontal or line-of-sight distance. If you’ve done much ISS-watching, you’ll notice that it’s brightest when somewhat east of the overhead point. That’s because the station is now opposite the sun and lit up fully like a full moon.
You can find the space station and get a map showing its path by using Heavens Above. Click the link, select your city and then tap the ISS link for a list of passes for the coming nights. Click on a date to see a map and timeline. Or go to NASA’s super-easy Spot the Station site for times. You can sign up there to get e-mail or text alerts whenever there’s a favorable pass over your city. Or you use an app like ISS Spotter for iPhone or ISS Detector for Android and customize your viewing. No matter which route you go, you can’t go wrong. I’ve included a table of pass times for the Duluth region is at the end of the blog.
If you’d like to try and photograph the ISS, you’ll need a tripod and a camera that can do a time exposure of at least 15 seconds. Set your lens to manual (M) and shutter to “M” as well. Get outside five minutes before the ISS arrives, focus on a bright star, then compose your image and wait for the station to pass through the frame.
For exposures longer than 30 seconds (the built-in limit even for many high-end cameras) you can either carefully hold down the shutter button with your finger or buy a remote release that you can click on for as long as you need. When using the release be sure you turn your shutter speed knob to “B,” the setting that lets you expose for as long as you want. I typically set my camera to ISO 800 and f/2.8 (wide-open) for 30 second-or-less exposures and ISO 400 and f/3.5 for those lasting between 1-2 minutes. Experiment in advance of the space station to see what gives you the best exposure.
Clear (if cold) skies!
The View From Duluth, Minn. (updated 1/29)
- Tues. Jan. 29: A low pass in the northern sky from 7:05-08 p.m. Watch for a dramatic disappearance in Earth’s shadow at 7:08.
- Weds. Jan. 30: Nice, bright pass across the northern sky from 6:14-18 p.m.
- Thurs. Jan. 31: Pass across the northern sky from 6:59-7:02 p.m. The station disappears in Earth’s shadow directly below the North Star.
- Fri. Feb. 1: Bright pass across the northern sky from 6:08-12 p.m.
- Sat. Feb. 2: Partial pass in the north from 6:53-56 p.m. with disappearance in Earth’s shadow