Guided learning / 4 lessons
Plan a night under the stars
Connect sky brightness, target altitude and observing conditions before building a target list.
Where this takes you
Leave with a shortlist of targets and a clearer idea of which conditions to check.
Follow the lessons ↓Lesson 1 / Interactive figure
The magnitude scale →
Learn the language used to describe apparent brightness.
Pause and consider
Use the magnitude figure to compare two stars. Which numerical value describes the brighter one?
Lesson 2
Light pollution and the Bortle scale →
Put the darkness of your observing site into context.
Pause and consider
What do you know about your site's sky brightness, and what would you still need to observe for yourself?
Lesson 3
Extinction and airmass →
Consider the atmosphere along your line of sight.
Pause and consider
Why might you prefer a target high in the sky over the same target near the horizon?
Lesson 4
Seeing →
Distinguish steady air from a dark sky.
Pause and consider
Describe how poor seeing and light pollution could affect an observation differently.
Put it into practice
Make a small target list
Open the deep-sky chart, choose your site and time, and inspect a target's altitude. Add a few targets to an imaging plan. Review the calculator's limits and check weather and Moon conditions separately.
Choose a target →