Observing Skills

Go out on a night you planned, give your eyes the dark they need, and read the sky’s brightest stars.

11 guides · about 70 min

A line runs from a guide to the guides that build on it.

1. 1. Bright Stars of the Season 6 min Which stars should you learn first, in a sky full of them?

   You’ll be able to go outside tonight and name the season’s five brightest stars.

   Begin
2. 2. Measure the Sky with Your Hand 5 min How can your hand at arm’s length measure the sky?

   You’ll be able to measure the gap between two stars, and a star’s height, with your hand at arm’s length.

   Leads to

   Planning a Night, The Southern Cross (How the Sky Turns), The Orion Nebula (Deep Sky)

   Begin Know it already? Find it outside
3. 3. Understanding Star Brightness 10 min Why does the brightest star in the night sky get a negative number?

   You’ll be able to estimate a star’s magnitude by eye, against stars you know.

   Leads to

   Planning a Night, Splitting Double Stars, Stars That Keep Time, Light Pollution, Satellites and the ISS (Visitors), A Visitor from Another Star (Visitors)

   Begin
4. 4. Dark Skies, Dark Eyes 6 min Why do more stars appear the longer you stay outside?

   You’ll be able to judge how dark your sky is, dark-adapt your eyes, and use averted vision.

   Leads to

   Planning a Night, Phone Photos of the Night, Finding the Andromeda Galaxy (Deep Sky)

   Begin
5. 5. Binoculars First 6 min Why is a pair of binoculars a better first instrument than a telescope?

   You’ll be able to read the numbers on a pair of binoculars, and find a cluster, a nebula, Jupiter’s moons and craters with them.

   Begin
6. 6. Planning a Night 7 min What should you check before you go out to look?

   You’ll be able to plan an observing night around the Moon, the weather and what is up.

   Builds on

   • Measure the Sky with Your Hand. It uses “altitude”, which Measure the Sky with Your Hand explains.
   • Understanding Star Brightness. It uses “magnitude”, which Understanding Star Brightness explains.
   • Dark Skies, Dark Eyes. It uses “bortle”, which Dark Skies, Dark Eyes explains.

   Begin Know it already? Find it outside
7. 7. Your First Telescope 6 min Why does a telescope’s width matter more than its magnification?

   You’ll be able to judge a telescope by its aperture, and work out its power, its field and its useful limit.

   Begin
8. 8. Splitting Double Stars 6 min How many stars is Mizar?

   You’ll be able to tell which double stars my eyes, binoculars or a small telescope will split.

   Builds on

   • Understanding Star Brightness. It uses “magnitude”, which Understanding Star Brightness explains.

   Begin
9. 9. Stars That Keep Time 6 min Which stars change brightness on a timetable?

   You’ll be able to catch Algol in eclipse and follow a Cepheid through its cycle.

   Builds on

   • Understanding Star Brightness. It uses “magnitude”, which Understanding Star Brightness explains.

   Begin
10. 10. Light Pollution 6 min Why does a city sky show so few stars, and how do you get them back?

    You’ll be able to say why a city hides its stars, read your sky’s limit, and win stars back from the glow.

    Builds on

    • Understanding Star Brightness. It uses “magnitude”, which Understanding Star Brightness explains.

    Begin
11. 11. Phone Photos of the Night 6 min Can the phone in your pocket photograph the stars?

    You’ll be able to photograph the stars, the Milky Way and the Moon with a phone, and work out an exposure with the 500 rule.

    Builds on

    • Dark Skies, Dark Eyes. It uses “bortle”, which Dark Skies, Dark Eyes explains.

    Begin