The Celestial Sphere

Question 1

What is the celestial sphere?

Answer 1

The grid of Right Ascension and Declination
It rotates once per day

Question 2

Along what line does the Sun travel?

Answer 2

Along the ecliptic which is inclined at 23 degrees to the equator
It takes 1 year for a full revolution

Question 3

When is the Sun at the most Northern part of the ecliptic?

Answer 3

At the summer solstice

Question 4

When is the Sun at the most Southern part of the ecliptic?

Answer 4

At the winter solstice

Question 5

For what range is RA?

Answer 5

0 to 360 degrees

Question 6

For what range is Dec?

Answer 6

-90 to 90 degrees

Question 7

What is the RA and Dec of the Sun at the Vernal equinox?

Answer 7

RA=0
Dec=0
21st March

Question 8

What is the RA and Dec of the Sun at the Summer solstice?

Answer 8

RA=90
Dec=23.5
21st June

Question 9

What is the RA and Dec of the Sun at the Autumn equinox?

Answer 9

RA=180
Dec=0
23rd September

Question 10

What is the RA and Dec of the Sun at the Winter Solstice?

Answer 10

RA=270
Dec=-23.5
21st December

Question 10

How do you work out the maximum altitude of an object?

Answer 10

alt_max=90∓(ϕ − δ) ,ϕ>δ, ϕ<δ
Where ϕ is the latitude of the observer and δ is the declination of the object

Question 11

What is a sidereal day?

Answer 11

The time for 1 full rotation of the Earth

Question 12

What is a solar day?

Answer 12

The time taken for the Sun to return to the same part of the sky

Question 13

What is the difference between a solar and sidereal day?

Answer 13

Solar day is longer by 4 mins