Checking a Compass

Question 1

How often should we check our compass?

Answer 1

Once per watch
After a large alteration of course

Question 2

How can we check our Compass?

Answer 2

Transit bearing
Amplitude of the sun at rising or setting
Azimuth of a Heavenly Body

Question 3

When checking the Magnetic compass, what in fact are we ensuring?

Answer 3

That the Compass card (deviation card) is in fact still valid and correct

Question 4

Procedure for checking a compass via a transit

Answer 4

1. Take a bearing of two objects in transit (in line) using the azimuth mirror
2. Compare this with the True transit bearing on the chart
3. High or low for Gyro
4. For magnetic, TVMDC, use Variation and Compass Error to find the Deviation

Question 5

Procedure for taking an Amplitude of the Sun
(now called azimuth of the sun at rising or setting)

Answer 5

1. Take a bearing of the sun using the Azimuth mirror/Peloras
   Do this when it is a semi diameter above the horizon
2. Note our Latitude/Time
3. Find the Declination of the Sun for the day in the Nautical Almanac
4. Enter the Latitude/Declination into the table in Norries, to find the T bearing of the Sun
5. Compare this with our observed Bearing to see our Gyro or Compass Error

Question 6

Procedure for checking the Compass via an Azimuth of a Heavenly Body

Answer 6

1. Take a Bearing of a heavenly body on the hour using the Azimuth mirror, note the time and Position
2. Find the Declination and GHA of that body
3. +/- current longitude to convert GHA to LHA
4. In sight reduction tables for current Latitude, enter LHA and DEC, to extract the T azimuth of that body
5. Compare this against your observed Azimuth to find the Error
6. Gyro high/low, Magnetic TVMDC

Question 7

Procedure for checking the Compass using Amplitude of the sun
(now called Azimuth of the sun at rising or setting)

Answer 7

1. Take a bearing of the sun at rising/setting, using the Azimuth Mirror or Peloras
   Do this when it is a semi diameter above the horizon
2. Note latitude and time
3. Find the Declination of the sun for that day in the Nautical Almanac
4. Enter DEC and LAT into The correct table in Norries to extract the. True azimuth of the sun
5. Compare this with the azimuth observed to find compass error
6. Gyro high/low, Magnetic compass TVMDC

Question 8

Define Amplitude of the Sun

Answer 8

How far the sun rises/sets, N or S of Due East/West