ObserveTheSky › Guides

Guides

Longer pages that cut across everything on this site — the solar system in one read, our galaxy in another, and lists of what is worth looking at.

If you want to do something

How to start astronomy with kids — eyes first, then binoculars, then one telescope
Your street to scale — the solar system paced out along a pavement
Build your own telescope — two lenses and a tube, and why it works

If you want to understand something

The solar system — one star, eight planets, and an enormous amount of empty space
The Milky Way — our own galaxy, and why it looks like a band from inside
Galaxies — the shapes there are, and what each shape means
The universe — how big, how old, and how anybody could possibly know
Why these yardsticks — why a moon is put beside a mountain and not beside a number

If you want to go and look at something

Everything you can actually see — sorted by what equipment it needs
What can I see tonight? — what to expect, and how to plan an evening
The ten most interesting objects — six of them with your own eyes or a small telescope
The constellations, and what is in them — 54 shapes, what is inside each, and how to hop between them
When the telescope will not behave — five faults, two symptoms each, and most of them not the telescope’s fault

If you are the grown-up

For teachers — what fits which lesson, and what makes it classroom-safe
For parents — where to start, and what to know before buying a telescope

Everything else

Explanations — 32 explanations of how anybody worked it out
A catalogue of every kind of thing — the taxonomy, generated from the database

🌙 Plan an evening outside

Every object, one by one

ObserveTheSky stickers to print

A sticker for a notebook, a telescope case or a classroom door — the Sun with its planets on their orbits, and a QR code that opens the site.

All the stickers, and every file

Go and watch it happen

Catch a moon’s shadow on JupiterAt an hour a second, a small black dot crosses Jupiter’s stripes every twenty seconds or so: a moon’s shadow on the planet. A 150 mm telescope shows the real thing.Catch Io’s volcanoes burningOnce a lap — about forty seconds at an hour a second — Io passes into Jupiter’s shadow for a few seconds, and orange points light up on it: its volcanoes. They show once Io fills a quarter of the screen (a view around 15,000 km across) with its night side towards you. No amateur telescope shows this, even in Jupiter’s shadow: the glow is mostly infrared and far too faint, and only spacecraft and the largest telescopes on Earth have caught it.Watch a star go out behind the MoonA star behind the Moon does not fade: it is simply gone between one blink and the next. From one garden it is rare and may be years away; “My next star or planet behind the Moon”, in the Coming up list, finds it.Catch the Moon’s shadow crossing the EarthThe view opens two hours before the total eclipse of 2 August 2027, looking from the Sun’s direction so the shadow is square on rather than seen at a slant. The dark middle is about 250 kilometres wide and crosses North Africa and Arabia. The clock runs ten minutes a second, so the dark middle crosses the Earth in about twenty seconds.Catch the Earth’s shadow on the MoonThe view opens two hours before the total eclipse of 31 December 2028, with the Moon filling the view. The umbral phase — the Earth’s dark inner shadow on the Moon — runs three and a half hours with an hour and a quarter of totality, the whole Moon inside it; at ten minutes a second that is twenty-one seconds of shadow and seven of copper. It is the one eclipse that needs no equipment at all outdoors.Watch Mars turn roundMars turns round on 10 January 2027 and turns back on 1 April, with 19 February in the middle: 81 days of going the wrong way, about nineteen degrees westwards against Leo — two fists held at arm’s length. The Earth is on the faster inside track and has overtaken it, the way a car you pass seems to slide backwards.Catch the Earth leaningCompare 21 December with 21 June, the Earth zoomed to fill the view: the sunlit half does not change size — it swaps ends. That tilt is why the Sun climbs higher here in summer and why the day is longer.