The sky as a sphere
- Sections
- 2 of 7 written
- Reading time
- 4 h 15 min
- Olympiad problems
- 4
- Part
- Theory
What the chapter covers
The celestial sphere, horizontal and equatorial coordinates, what can be seen from a given latitude, the astronomical triangle, ecliptic and galactic coordinates.
IOAA syllabus. Coordinates and time: spherical trigonometry; celestial coordinates and their applications; equinoxes and solstices; circumpolar stars; constellations and the zodiac.
Builds on. Angles and spherical triangles from the maths toolkit (Section S3).
Share of the marks. Positional astronomy and time, which this chapter shares with Chapter 2, carry about 15% of the theory marks in the official problem book, the largest share of any topic.
| No. | Section | Reading time | Status |
|---|---|---|---|
| 1.1 | The celestial sphere | 25 min | Not started |
| 1.2 | Altitude and azimuth | 20 min | Not written yet |
| 1.3 | Right ascension, declination and hour angle | 40 min | Not written yet |
| 1.4 | What you can see from where you stand | 35 min | Not started |
| 1.5 | The astronomical triangle | 50 min | Not written yet |
| 1.6 | Ecliptic and galactic coordinates | 25 min | Not written yet |
| 1.7 | Problems for Chapter 1 | 1 h | Not written yet |
| Year | Problem | Points | Section |
|---|---|---|---|
| 2020 | Astrophotography | 10 | 1.1 |
| 2007 | The smallest shift | 2 | 1.1 |
| 2022 | Georgia to Georgia | 20 | 1.4 |
| 2024 | Castaway | 20 | 1.4 |
Entry check and chapter test
The five-question entry check, which marks each section skip, skim or study, and the ten-question chapter test are written with the rest of this chapter.