Stargazing 101: Understanding the Night Sky Quiz

Answer: 23.5 degrees

Far from stable, the Earth's axial tilt ranges from 22.1 to 24.5 degrees over cycles of about 41000 years. In the first quarter of the twenty-first century, we are about halfway through the cycle, and are expected to reach the minimum tilt in the year 11800 CE.

Answer: Celestial sphere

In reality, the distance to stars and galaxies varies widely. However, the celestial sphere remains a very useful model to specify the location of objects in the sky. This is because the distances are so large that parallax errors are largely undetectable.

Nearby objects within the solar system (the sun, moon, planets, etc.) are not considered to be part of the celestial sphere as they are so close that they move through the sphere over time.

Answer: 60 arcseconds

Arcseconds can be further subdivided into 1,000 milliarcseconds and 1,000,000 microarcseconds for further precision. However, in practice it is often preferred to use decimals of a minute to provide the necessary significant figures of precision e.g. 35 degrees 12.235233 arcminutes.

Answer: Altitude and azimuth

The system is useful to simplify navigation in a local sky. However, its use is limited as the coordinates of an object will vary throughout the night as the Earth rotates, and will also vary in different observing locations.

Answer: Declination and right ascension

This system allows for a single universal coordinate that stays consistent at any time of the night and any location on Earth. It is a geocentric model that uses the centre of the Earth, the plane through the equator, and the spring equinox as reference points.

Answer: Polaris

Located within one degree of the north celestial pole, Polaris is conveniently placed for Northern hemisphere stargazers. However, due to precession of the equinoxes, Polaris only occupies this position for a few thousand years at a time over a 26,000 year cycle. Over a dozen other stars will become closest to the north celestial pole over this cycle, and indeed ancient stargazers looked up to Kochab to mark this point.

Answer: Look at the horizon due SOUTH, then move up at the angle equal to your LATITUDE.

Sigma Octantis currently marks the south celestial pole, but it is barely visible to the naked eye even on a clear night. A common alternative method to roughly identify the south celestial pole involves finding the intersection of the long axis of the Southern Cross and the perpendicular bisector of the Southern Pointers. Even this point is still 5 degrees away from the pole!

Answer: North - anti-clockwise; South - clockwise

Popular in astrophotography, star trail photographs rely on this rotational motion to create stunning time-lapse images of stars streaking across the sky. Observers near the equator can witness both the anti-clockwise motion of the northern stars and the clockwise motion of the southern stars depending on which direction they look.

Answer: Nearly six months

Due to the tilt of the Earth, the poles are angled away from the sun for six months at a time. This makes the poles perfect for stargazing in their respective winters, if you can brave the cold! Conversely, during summer there is continuous day time, which may limit your stargazing opportunities.

Answer: The Moon's orbit around the Earth is inclined by 5 degrees to the Earth's orbit around the Sun which means it only occasionally aligns exactly with the Earth and Sun

This is the same reason that we don't get solar eclipses every month. It also helps account for the various types of eclipse that we observe - penumbral, partial, total and central. The closer the Moon is to crossing directly behind the Earth (with respect to the Sun), the more complete the eclipse.