Observing the Night Sky

Question 1

What is Declination (Dec)?

Answer 1

• If we imagine the Earth at the centre of a giant celestial sphere, declination is almost identical to Latitude.
• It is a projection of latitude onto the sphere.
• It is the angle of a point above the celestial equator.
• The Declination of a star never changes!

Question 2

What is Right Ascension?

Answer 2

• The RA of a star is the angle between it and the celestial prime meridian.
• It is measured in hours and minutes.

Question 3

What is the Celestial Prime Meridian?

Answer 3

-This is the point on the celestial equator on which the sun moves from the southern to the northern hemisphere. Spring Equinox (March 21st)

Question 4

What is the Zodiacal Band?

Answer 4

• This is the part of the sky that contains the constellations of the zodiac and is the region in which the planets and Moon are located.
• It straddles the Ecliptic by 8 degrees on either side.

Question 5

How do you find your latitude using Polaris?

Answer 5

Measure the angular elevation of Polaris from the Northern Horizon.

Question 6

Which way do stars appear to rotate about Polaris?

Answer 6

Anticlockwise

Question 7

How can we determine if a star will be circumpolar using the observer’s latitude and the star’s declination?

Answer 7

Declination > 90 – latitude

Question 8

What is a circumpolar star?

Answer 8

• This is a star that does not set.
• It is above the observer’s horizon all the time.
• Which stars are circumpolar depends on the observer’s horizon.

Question 9

Explain how a star will be circumpolar from a given latitude so long as the declination is > 90 -latitude

Answer 9

My latitude is 52 degrees, 90-52 = 38 degrees

Therefore any star with a declination >38 degrees will be circumpolar.

Question 10

Name considerations when planning an observation.

Answer 10

• Phase of the moon
• Weather
• Likely-hood of a meteor shower
• Visibility of a planet, Messier/comet
• Equipment

Question 11

Who was Charles Messier?

Answer 11

• Compiled a list of 110 “fuzzy” objects in the sky.

- Named “Ferret of Comets”.