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Popular Astronomy Magazine - March-April 2017
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Simple Guide to Viewing the Space Station

Amateur astronomers have been enjoying watching the International Space Station drifting across the sky for years now. For many, it’s become as enjoyable a part of the hobby as watching a meteor shower or just standing outside under the stars on a clear night. 

If you’re one of the many people who want to start doing this, but don’t know how or when to see the space station in the sky, this simple SPA Guide is for you.

First, what exactly IS the ISS?

The ISS is a high tech laboratory, orbiting the Earth at around 17,000 mph at almost 300 miles up in space, where astronauts live, work and do experiments. To look at it, you’d think it was a huge Meccano model, and in a way it is – a multi-billion dollar model built over many years, by different countries. Its pieces were all joined together in space, making it Mankind’s most ambitious, complicated and risky construction project ever.

If you look at photos of the ISS you’ll see it looks nothing like the graceful, wheel-shaped space stations seen in science fiction films like “2001 A Space Odyssey”. That’s because a) we can’t afford to build one of those, and b) in real life, spacecraft don’t need to be pretty, they just have to work. The ISS is made of many different parts, and has bits sticking out of it everywhere. The most obvious parts are the huge “wings” on either side are its solar arrays – these power the space station by collecting energy from the Sun. Between the solar array “wings” are lots of tubes or cylinders, all joined together, called “modules”. These are the rooms and laboratories the astronauts live and work in. As they’re pressurised, like the inside of an airliner, the astronauts don’t need to wear spacesuits, they just wear normal clothing. If they go outside they put on a spacesuit.

That’s what the ISS is. But how come we can see something so far away, so high above the Earth?

Well, because it’s so high the ISS is still bathed in sunlight long after darkness has fallen down here on the ground. That sunlight reflects off its enormous solar panel “wings”, just like sunlight glints off an airplane, or a mirror.  That’s what makes it (and other satellites) visible to us in our night sky.

In recent years, the ISS has grown larger and brighter, and is now frequently so bright that you don’t need to be an astronomer – with a deep knowledge of the night sky and expensive equipment – to enjoy following it as it flies through the sky. All you need to know is what time to start looking for it.

What equipment do I need?

NONE! The best thing about ISS-spotting is that you don’t need a telescope – in fact a telescope is pretty useless for ISS-spotting because the ISS moves so quickly  it’s very hard to keep it in a telescope’s high magnification eyepiece. If you have a pair of binoculars though, you should definitely try training them on the ISS – they will make it look much bigger and brighter, and enhance its colours too. ( Colours? Yes; those highly reflective solar panels are made of a shiny gold material, and they give the ISS a golden hue as it crosses the sky. When the station starts to fade, it can turn – especially in binoculars – a dark ruddy colour, and looks like a fading ember in the darkness of the night…)

Ok, so having read all that I’m sure you want to see the ISS for yourself! What exactly do you do? To see the ISS you need to do the following:

1. Find out what time the ISS will rise above your local horizon (see below).

2. Go outside at least 5 minutes BEFORE that time to let your eyes get used to the darkness.

3. Face the WEST (ish… sometimes the ISS rises in the SW, but face roughly west and you won’t go far wrong)… and wait. Eventually you’ll see a “star” rising up from behind that western horizon, ormoving just above it. That will be the ISS!

4. Just watch the ISS drift across the sky, and enjoy it! 

Simple, isn’t it?

Well, yes, it is, but there are some extra things you need to know. Firstly, the ISS isn’t visible EVERY night. There are ISS spotting “periods”, blocks of a week or so when it is clearly visible in the sky.  And it’s not exclusive to the NIGHT sky, either; sometimes it is visible before sunrise instead of after sunset, so you’re looking for it in the very early hours instead of after dusk.

It’s also very important to know that not every “pass” of the ISS is spectacular. Sometimes it flies almost overhead, but on other “passes” it only climbs slightly above our horizon. During a “high” pass the ISS can appear stunningly bright, so bright it can cast shadows from a dark site, but during a “low” pass it looks barely brighter than the bright stars in the sky beyond it. The BEST passes to observe are the ones when the ISS is going to be high above the horizon, because that’s when it will be most fully illuminated by the Sun, and visible for several minutes.

That probably sounds very confusing, so how are you supposed to know when to look? Well, there are several websites on the internet that will tell you exactly when and where to look for the ISS after you’ve entered your location. And now, you can use apps on smartphones and tablets to find out the times in advance too. More on those later.

Okay, let’s look at the most important part of the whole thing – how you find the times of ISS “passes” visible from where you are.  

All you have to do is go to a website that calculates the times of ISS passes for your area. You either a) select your town or city’s name from the site’s list, or b) enter your geographical co-ordinates, and then the website does the rest.

Here are the best websites I’ve found for predicting the times when the ISS will be visible from where you are.

 NASA’s Satellite Prediction website

This is obviously geared towards US viewers, but if you look on the bottom right of the opening screen  you’ll see there’s a list of some popular cities across the world. Find one near you, click on the link, and you’ll be taken to a page telling you the date and time when the ISS will be visible, when to start looking, how long the space station will be in the sky for, how high it will get in the sky, and when it will vanish from view again – all you need to see the space station! What it doesn’t tell you is how bright the ISS will appear, but you can figure that out for yourself by just looking at the figures for “Maximum height”, etc. The longer the ISS is in the sky for, and the higher it is in the sky, the brighter it will appear. Simple! Using that NASA website you will be guaranteed never to miss a good “pass” of the space station again – well, when the sky’s clear enough to let you see it, that is…

The website most ISS-spotters use though is Heavens Above, because it gives the most accurate predictions, and also lets you see a chart of the sky, showing exactly where the ISS will be. You have to do a little more work to get started, but it’s worth it.

When you go to the website you’ll see a link called “Configuration”. That’s where you enter your viewing location. It’s really very easy – you can either dive straight into the site’s huge database of countries, cities and towns, or use a global map to identify your viewing location. After you’ve let the site know where you live, and chosen “ISS” from the “10 day predictions” list under “Satellites”, you’ll be presented with a page packed with information - rising direction and time, highest point, and more. But what makes this site worth using more than anything else is its chart-generating capability. If you click on one of the dates written in blue, over there on the left of the table, you even get a very useful chart that shows you where the ISS will be in the sky in relation to the brightest stars and, if they’re visible, the Moon and planets too.

Admittedly the Heavens-Above tables take a bit of understanding, so here's a  guide to working out what all those degrees and azimuths mean. It also gives a short guide to photographing the station if you have a suitable camera.

Whichever site you use, start looking for the ISS shortly before the time given by the website, don’t leave it until the last minute. Sometimes the ISS can appear slightly early, so you don’t want to miss it. Equally, PLEASE BE PATIENT! Keep watching until you see it – don’t give up after a couple of minutes and go back inside.

Finally, a couple of observing tips:

* Although you can see the ISS easily from your garden, or front doorstep, if you possibly can, find somewhere dark to watch a pass from, especially one of the brightest passes. It will look much better from there than it would from somewhere with houses and lights all around you.

* If you have binoculars, take a look at the ISS through them. You won’t see its solar panels, or modules, but its brightness and colours will be greatly enhanced.

Finally, a word about using Apps on smartphones and tablets. A quick search for apps called something like “ISS tracker” or “Satellite tracker” or just “Space station” on the apps stores for both iOS and Android operating systems will show you there are lots to choose from. Like the website, the one I recommend above all others is the “Heavens Above” app, because it is the easiest to use and most reliable.

OK, that’s it. Good luck, let us know if you see it – and don’t forget to give the astronauts a wave!

Stuart Atkinson


Other articles of interest:

Transit of Mercury 2016

Giving long exposures on a digital camera

Photographing star trails

Predicting the ISS and other satellites

Using a mirror to view a partial eclipse

Simple Guide to Viewing the Space Station

Choosing a Telescope

Tips when projecting the Sun

Starting to Use Your Telescope

Imaging with a DSLR through the telescope

Buying a telescope for a child

Photographing a partial eclipse



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