It’s the Same Sky Everywhere

One of the most remarkable things about astronomy is that it’s all the same sky, everywhere. The night sky you see is the same night sky that the most massive telescopes in the world see. For instance, here’s a picture of Jupiter I took with my DSLR in my apartment.

Jupiter, and four moons!
Jupiter, and four moons, as seen from my apartment.

This is a product of me being awake at an unreasonably early hour recently, during the recent conjunction of Mars, Jupiter, and Venus – three planets visible in the early morning sky, incredibly bright specks visible from even the middle of a city.

Just like that I can see why Jupiter’s moons were among the very first things Galileo saw. I’m not even using a telescope and I can see them.

Of course, back in his day, Galileo was on his own when it came to figuring out WHAT he was seeing… I can just load up Stellarium, put in my location and the date and time, and find out which moon is which:

Jupiter, that morning, as simulated by Stellarium.

Presto! There they are. Stellarium is a free software program that simulates the night sky. It uses a very accurate model of the Solar System and of the Earth’s rotation to show you anywhere on the sky, as seen from anywhere on Earth, at any time and date within a few thousand years of now. It’s used in planetariums and it’s generally extremely accurate in both position and brightness. And it confirms I really did see the moons of Jupiter.

All I had was a DSLR and a tripod, using manual focus (which I had to use trial and error to get right – you want the stars to be the smallest points they could possibly be) and a manual 1 second exposure. I didn’t even have a clock drive to match the Earth’s rotation (so I guess it’s good I have a DSLR with a nice big lens, otherwise I would have had to expose for longer, and the moons would have been even bigger streaks). I used a 300mm equivalent zoom lens, but given how clearly the moons showed up it looks like I could have gotten away with much less than that. Your point and shoot may even be able to do it, if it can do a long enough exposure, focus on infinity, and you can set it on a tripod.

It’s not magic, folks. When astronomers go out and look at the sky, they’re looking at the same sky everyone sees, just under higher magnification and with more light-gathering power. But it’s all there – all of it. The rings of Saturn, the Hubble Deep Field, exoplanets (although those guys REALLY shouldn’t be considered ‘amateurs’)… It’s all out there, somewhere. And it’s all within your reach too.

The full original image

2 Comments Add yours

  1. I haven’t used Stellarium. Looks interesting. I have dabbled with Celestia, which does much the same thing at enthusiast level but is getting a bit dated now.

    Liked by 1 person

  2. Dragallur says:

    Cool I was using Celestia too, pretty neat. I will try this one probably!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s