(E) Knowledge gaps PAPER 1

Question 1

What is the lunar distance method?

Answer 1

It involves calculating the distance between the moon and a prominent star to find the navigator’s longitude.

Question 2

What are some flaws of the lunar distance method?

Answer 2

• Depends on a clear sky
• Accurate measurements being taken at sea
• The Earth is NOT uniformly spherical
• Early tables had a larger margin of error than later versions

Question 3

What’s the most prominent star(s) in Cygnus?

Answer 3

Deneb

Question 4

What’s the most prominent star(s) in Crux?

Answer 4

Mimosa, Acrux

Question 5

What’s the most prominent star(s) in Cassiopeia?

Answer 5

Schedar

Question 6

What’s the most prominent star(s) in The summer triangle?

Answer 6

Deneb, Vega and Altair

Question 7

What’s the most prominent star(s) in The great square of Pegasus?

Answer 7

Alpheratz

Question 8

What’s the most prominent star(s) in The Plough?

Answer 8

Dubhe

Question 9

How many degrees is the Earths axis tilted to the ecliptic by?

Answer 9

23.5 degrees

Question 10

What is the First point of Libra?

Answer 10

The point at which the sun on the ecliptic crosses the celestial equator at the autumnal equinox

Question 11

What is the First point of Aries?

Answer 11

The point at which the sun on the ecliptic crosses the celestial equator at the vernal equinox

Question 12

How can we work out the sun’s altitude?

Answer 12

Sun Altitude = Sun Declination + (90° - Latitude of Observer)

Question 13

What’s the equatorial coordinate system?

Answer 13

RA and Declination

Question 14

What’s the horizontal coordinate system?

Answer 14

Altitude and Azimuth

Question 15

How many constellations does the sun cross in a year?

Answer 15

13

Question 16

Difference between Meteor, Meteoroid, Meteorite?

Answer 16

Meteor: In space
Meteoroid: In atmosphere
Meteorite: On Earth

Question 17

Where are star maps usually found?

Answer 17

Star maps and charts are published in books, newspapers and magazines

Question 18

How are brighter/smaller stars presented on star maps?

Answer 18

brighter stars = larger dot
smaller stars = smaller dot

Question 19

What is the purpose of a planisphere?

Answer 19

To find out what stars are viewable at any time

Question 20

What is the structure of a planisphere?

Answer 20

Two discs fastened to each other

Top disk:
—-> On one of them is a hole (so that a portion of the disc underneath can be seen)
—-> Around the edge are hours of the day

Underneath disk:
—-> A star map showing every constellation available for viewing from a general location

Question 21

What does the edge of the round area represent on a planisphere?

Answer 21

The horizon

Question 22

What are the two discs fixated at on a planisphere?

Answer 22

The pole axis

Question 23

How would you use a planisphere?

Answer 23

1. To find the stars available on 4th September at 10pm you would move the hour dial that says 10pm on the overlay next to the date on the underlay
2. Point the planisphere north