Surprisingly, you don’t even need a telescope to see the International Space Station. It’s also easier than you might expect to know where and when to look for it.
A Quick Primer on the ISS
The International Space Station (ISS) is a crewed space station built and maintained as a collaborative effort between the USA, Canada, Russia, Japan, and the 23 countries who make up the European Space Agency.
It serves as an observatory and laboratory for experiments which cannot be carried out on Earth, either because they require microgravity or can only operate in space. The latter includes the Alpha Magnetic Spectrometer (AMS), intended to detect dark matter.
The ISS orbits at an altitude of between 230 and 280 miles at an inclination of 51.6°, meaning it flies over 90% of the inhabited areas of the Earth at various times. It travels at 17,500mph, which equates to one orbit every 93 minutes, or circling the Earth 15.5 times per day. The net result of all this is that the ISS is visible from almost anywhere on the planet if you look in the right direction at the right time.
What You Need to See the ISS
The space station is visible to the naked eye. What you are actually seeing is sunlight reflected from the solar panels, so it will look similar in appearance to a meteorite—a fast-moving light in the sky.
Because we need sunlight to be reflected from the panels back to our position on the Earth, and because the reflected light will only be visible against a dark sky, the two opportunities to see it are at dawn and dusk. In daylight, it just isn’t bright enough, and in the middle of the night it will be in the shadow of the Earth.
You also need a location without too much light pollution, so if you live in a city or large town you may need to travel some way into the countryside for the best chance to see it.
Finally, you need clear skies. If you can’t see stars, then you probably won’t be able to see the ISS.
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If you want a better view than you can get with the naked eye, then things get tricky because the ISS moves so quickly across the sky. This makes it almost impossible to view through a manual telescope, as the field of view is too small to first find it and then track its movement. Binoculars, which have a wider field of view, are a better bet, but it can still be rather difficult. If you want to try, then NASA’s app (detailed below) is almost essential.
The Rolls-Royce solution is a telescope on a sophisticated motorized mount (like the Sky-Watcher AZ-EQ5) which can automatically track the position of the ISS for you. The cost of a setup like this runs into four figures and only really makes sense if you want to get seriously into astronomy too.
How to Know Where and When to Look
Depending on where you are and the time of year, viewing opportunities can range from once a month to several times a week.
There’s a great astronomy app from NASA which tells you where and when to look: Spot The Station. It’s available for iPhone and Android, and provides 2D and 3D real-time views of the current location of the ISS, with a countdown timer until the station is next visible at your location. You can also opt to have the app send you a notification of each viewing opportunity.
Once the ISS is visible, you simply orient your smartphone in the direction of the on-screen arrow until you see a graphic of the station. It overlays both the past and projected path of the station, making it easy to find.
Alternatively, you can sign up for email or text alerts from NASA. You’ll be prompted to select your location, your mobile carrier (for texts), and whether you want alerts in the morning, evening, or both. Note that because the morning alerts are before sunrise, they will often be very early indeed! The alerts comprise five pieces of information:
- Time: When the viewing window begins.
- Visible: The duration of the viewing window.
- Max Height: The elevation in degrees (where the horizon is 0 degrees and directly overhead is 90 degrees).
- Appears: The compass direction when first visible (e.g., WNW means west by northwest).
- Disappears: The compass direction when last visible.
Why You Don’t Always Get Alerts When the ISS Passes Over
NASA only alerts you when the transit is at dawn or dusk and the maximum inclination of the station from your location is at least 40 degrees. Below this, there’s a high chance that your view will be blocked by hills or buildings. NASA therefore limits the alerts to avoid disappointment.
How to Know You’re Seeing the ISS and Not a Plane or Meteor
If a plane is far enough away that it cannot be identified, then it will move relatively slowly across the sky. You may also be able to see flashing strobe lights.
A meteor, colloquially known as a shooting star, will typically be visible very briefly, and the intensity of the light will flicker.
If the light is fast but relatively steady, then you are likely looking at the ISS. Nevertheless, the best approach is to use NASA’s app so you know you’re looking in the right place at the right time.
How to Best Photograph the ISS
NASA’s Spot The Station app has a built-in camera feature, so you can capture what you see.
However, photos and video will be rather underwhelming unless you are using a very long lens, and that requires the same specialist tracking mounts we mentioned earlier. But if you are sufficiently keen, and have the budget, then capturing transits across either the Moon or the Sun provides the best photo opportunities; you do need the appropriate filters to shoot into the Sun.
Needless to say, never look into the Sun either directly or through a camera without a filter certified for solar viewing.
The simplest approach is to download NASA’s app, allow notifications, and then take a look next time you get an alert when there are clear skies and not much light pollution at your location.
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