Did you know the International Space Station is among the easiest-to-spot extraterrestrial objects? After the Sun and the Moon, the International Space Station is the third brightest object in the sky and so, quite easy to spot. All spotting the International Space Station requires is a cloudless sky and timing -- the space station should be flying over your city at a visible enough angle a few hours after sunset or before sunrise.

The latter of the two requirements -- timing -- will be fulfilled tonight for the cities of Rajkot and Ahmedabad in Gujarat, Jaipur in Rajasthan, and Delhi. In fact, it's going to be as perfect as it can be.

Tonight, the International Space Station will be flying over these cities at an angle of nearly 90 degrees, i.e. the ISS will pass right over your head, giving you the perfect opportunity to get a sighting of the International Space Station in the sky.

This, by the way, is not as rare as you'd think. And, if you live in cities other than the ones mentioned above, fret not. But before we talk about the whys and hows of these two points, let's go through a brief guide on spotting the International Space Station tomorrow.

When will International Space Station be visible?

In Rajkot and Ahmedabad, the International Space station will 'rise' at around 8:35 pm Tuesday. In the other cities -- Jaipur and Delhi -- this will take place closer to 8:37 pm.

Viewing International Space Station: Where can I see it?

The ISS will begin rising from the southwest horizon, i.e. if you're standing facing the South, the space station will appear somewhere to your 1-2 o'clock.

How much time will I have?

Six minutes. That's how long the International Space Station will be visible in the skies of Rajkot, Ahmedabad, Jaipur and Delhi.

How will the International Space Station look like?

The International Space Station is the third brightest object in the sky (Photo courtesy: Dave Walker)

Like we told you earlier, the ISS is the third-brightest object in the sky. It will appear like a star, but much brighter, and will be seen flying by like an aeroplane, but much faster.

If you're in the cities mentioned above, you will basically see a bright, star-like object rising from the horizon, darting across the night sky, passing right over your head, before dipping and 'setting' into the opposite side of the horizon.

WHY ONLY THESE CITIES?

Rajkot, Ahmedabad, Jaipur and Delhi are simply the cities that will have the best possible view of the ISS Tuesday night, with the space station passing above your heads. Towns and cities located within an 80-km radius of these places will also have a similar view.

Others located a little far off, such as Vadodara, Indore, Agra, Dehradun and Chandigarh will also be able to view the International Space Station; it's just that ISS won't pass directly overhead and will be seen at an angle.

Other cities will get their turn in the future, like we explain in the section below.

NOT A RARE EVENT

The International Space Station orbits around the Earth approximately 16 times a day. What this means is that there are plenty of opportunities to spot the ISS in the sky. All you require is cloudless skies and the space station passing over your city at a comfortable angle, sometime after or before sunset.

What does that mean? Think of the horizon being 0 degrees and a point in the sky right above your head being 90 degrees. The ISS can appear at any angle between these. Nasa says that the best possible angle to view the ISS is 40 degrees or more since that will ensure obstructions such as tall buildings don't get in the line of your sight.

The International Space Station seen flying in the night sky (Photo courtesy: Wayne Boyd)

It is also important that the ISS passes over your city a few hours after or before sunset. This ensures that enough sunlight bounces off the space station for it to be visible in the night sky.

Sounds extremely difficult to calculate, right? Which is why Nasa does it for the world. The space agency has a website -- Spot The Station -- dedicated to tracking the movements of the International Space Station and telling you the best suitable time to view the ISS in the coming week.

So, while Mumbai will be missing out on viewing the International Space Station Tuesday night, it will be able to see the spectacle -- at the same overhead angle -- early Thursday morning later in the week.

Of course, you won't be able to capture images like the ones we've shown you above with your smartphone, but it will be quite a sight to actually see.

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International Space Station from Earth: Perfect sighting for Ahmedabad, Jaipur, Delhi tonight | What to know - India Today