Ephemeral lrg

Grunt Productions 2007
Time, Rise/Set andTime, Rise/Set and
Gyro ChecksGyro Checks
Using data in the NauticalUsing data in the Nautical
AlmanacAlmanac
A brief by Lance GrindleyA brief by Lance Grindley

CoveringCovering
 Time and time zones including questionsTime and time zones including questions
on passage planning.on passage planning.
 Rising and setting, twilights and MoonriseRising and setting, twilights and Moonrise
or Moonsetor Moonset
 Gyro checks at Sunrise or Sunset usingGyro checks at Sunrise or Sunset using
the True Amplitude Tables (Nories)the True Amplitude Tables (Nories)

Earth’s Annual OrbitEarth’s Annual Orbit
Winter
Solstice
Summer
Solstice

Earth’s RotationEarth’s Rotation
 Earth rotates 360Earth rotates 360oo
in 24 hours = 15in 24 hours = 15oo
per hour.per hour.
 The Sun moves through 15The Sun moves through 15oo
ofof
longitude every hour - called Arc tolongitude every hour - called Arc to
Time.Time.
 Used as a basic division of StandardUsed as a basic division of Standard
Time Zones which are divided intoTime Zones which are divided into
areas 15° in longitude across.areas 15° in longitude across.

Uniform Time SystemUniform Time System
 Conceived to ensure all vessels at seaConceived to ensure all vessels at sea
within same area are keeping the samewithin same area are keeping the same
zone timezone time
 Based on Solar Day 360Based on Solar Day 360oo
in 24 hoursin 24 hours
gives 15gives 15oo
per hourper hour
 Zones are described in ALRS Vol. 2Zones are described in ALRS Vol. 2
page 255page 255
 Ships may not necessarily keep toShips may not necessarily keep to
these Standard Time Zonesthese Standard Time Zones

Standard Time ZonesStandard Time Zones

Time Zone ConventionsTime Zone Conventions
 Time zones usually designatedTime zones usually designated
numerically by indicating correction tonumerically by indicating correction to
zone time to obtain GMTzone time to obtain GMT
 Easterly zones negative, westerlyEasterly zones negative, westerly
zones positivezones positive
 May be indicated by letter Z for GMT, AMay be indicated by letter Z for GMT, A
to M increasing easterly (omitting J), Nto M increasing easterly (omitting J), N
to Y increasing westerlyto Y increasing westerly

Standard Time Zones (1)Standard Time Zones (1)
Greenwich
71
/2
o
W 71
/2
o
E 221
/2
o
E 371
/2
o
E221
/2
o
W371
/2
o
W
12001100100009000800
(-2)
B
(-1)
A
(0)
Z
(+1)
N
(+2)
O

Greenwich
71
/2
o
W 71
/2
o
E 221
/2
o
E 371
/2
o
E221
/2
o
W371
/2
o
W
13001200110010000900
(-2)
B
(-1)
A
(0)
Z
(+1)
N
(+2)
O

Greenwich
71
/2
o
W 71
/2
o
E 221
/2
o
E 371
/2
o
E221
/2
o
W371
/2
o
W
14001300120011001000
(-2)
B
(-1)
A
(0)
Z
(+1)
N
(+2)
O

Greenwich
71
/2
o
W 71
/2
o
E 221
/2
o
E 371
/2
o
E221
/2
o
W371
/2
o
W
15001400130012001100
(-2)
B
(-1)
A
(0)
Z
(+1)
N
(+2)
O

Greenwich
71
/2
o
W 71
/2
o
E 221
/2
o
E 371
/2
o
E221
/2
o
W371
/2
o
W
16001500140013001200
(-2)
B
(-1)
A
(0)
Z
(+1)
N
(+2)
O

Some Definitions of TimeSome Definitions of Time
 Universal Time (UT1) is the Mean Solar TimeUniversal Time (UT1) is the Mean Solar Time
of the prime meridian obtained by directof the prime meridian obtained by direct
astronomical observationastronomical observation
 Greenwich Mean Time generally equivalent toGreenwich Mean Time generally equivalent to
UT1 and used to define angular positionUT1 and used to define angular position
relative to the prime meridianrelative to the prime meridian
 International Atomic Time (TA1) based onInternational Atomic Time (TA1) based on
Cesium clock - very accurate but notCesium clock - very accurate but not
corrected for polar variation - hence leapcorrected for polar variation - hence leap
secondsseconds

Legal TimeLegal Time
 Decreed time zone for each territory.Decreed time zone for each territory.
 May not conform to the longitude as legalMay not conform to the longitude as legal
time is adjusted for political andtime is adjusted for political and
commercial reasons.commercial reasons.
 Many countries employ daylight savingMany countries employ daylight saving
time (DST) when clocks are advanced bytime (DST) when clocks are advanced by
one hour.one hour.
 Dates for DST must be checked in theDates for DST must be checked in the
Table of Legal Time.Table of Legal Time.

Passage CalculationsPassage Calculations
 Work out how long the passage will take.Work out how long the passage will take.
 Add the Time in Hand (TIH)Add the Time in Hand (TIH)
 This gives total time period of the passageThis gives total time period of the passage
 Convert ETA/ETD to ZULU Time.Convert ETA/ETD to ZULU Time.
 Add/subtract total passage time.Add/subtract total passage time.
 Convert ETD/ETA to Legal TimeConvert ETD/ETA to Legal Time
 NB Legal to Zulu follow sign - Zulu to LegalNB Legal to Zulu follow sign - Zulu to Legal
reverse the signreverse the sign

ExampleExample
 D14. Your ship is leaving WELLINGTOND14. Your ship is leaving WELLINGTON
(New Zealand) at 1000 local time on 7 Feb(New Zealand) at 1000 local time on 7 Feb
98, bound for PANAMA, a distance of98, bound for PANAMA, a distance of
6,480 nautical miles. Allowing a passage6,480 nautical miles. Allowing a passage
speed of 12 knots, and allowing a zerospeed of 12 knots, and allowing a zero
TIH for one hour per day or part of a day,TIH for one hour per day or part of a day,
also allow 8 hours for refuelling at sea,also allow 8 hours for refuelling at sea,
what is your ETA?what is your ETA?

Example - WorkingExample - Working
 6,480nm @ 12 knots = 540 hours = 22d 12h6,480nm @ 12 knots = 540 hours = 22d 12h
 Time in hand 23 hrs plus 8 hrs =Time in hand 23 hrs plus 8 hrs = 1d 07h1d 07h
 Total time on passage = 23d 19hTotal time on passage = 23d 19h
 ETD Wellington 071000(-13) 062100Z FEBETD Wellington 071000(-13) 062100Z FEB
 Passage +Passage +231900231900
 ETA Panama 021600Z MARETA Panama 021600Z MAR
 Legal Time Zone (+5)Legal Time Zone (+5) -0500-0500
 ETA PanamaETA Panama 021100(+5)021100(+5)

Changing Time ZonesChanging Time Zones
 A ship keeping the Standard Time Zone forA ship keeping the Standard Time Zone for
6060oo
West is due to arrive at PARAMARIBOWest is due to arrive at PARAMARIBO
(Suriname). How must the clocks be altered(Suriname). How must the clocks be altered
before entering harbour?before entering harbour?
 Time Zone for 60Time Zone for 60oo
W Zone (+4)W Zone (+4)
 Time Zone in Suriname (+3)Time Zone in Suriname (+3)
 Move from 4 hours behind GMT to 3 hoursMove from 4 hours behind GMT to 3 hours
behind GMT, therefore clocksbehind GMT, therefore clocks advanced byadvanced by
one hour.one hour.

Alternative CalculationAlternative Calculation
Ship’s time assumed to be 1200 (+4)
Converted to GMT 1600
New Time Zone Suriname (+3) -3 hours
New time in Zone (+3) 1300
Clocks need to be advanced one hour
from 1200 to 1300.

Sunrise/SunsetSunrise/Sunset
 Basis of tabulationsBasis of tabulations. At sunrise and. At sunrise and
sunset 16’ is allowed for semi-diametersunset 16’ is allowed for semi-diameter
and 34’ for horizontal refraction, so that atand 34’ for horizontal refraction, so that at
the times given the Sun’s upper limb is onthe times given the Sun’s upper limb is on
the visible horizon; all time refer to thethe visible horizon; all time refer to the
phenomena as seen from sea level with aphenomena as seen from sea level with a
clear horizon.clear horizon.
 ((Nautical AlmanacNautical Almanac))

Northerly DeclinationNortherly Declination
N S
E
W
P

Southerly DeclinationSoutherly Declination
N S
E
W
P

Effect of DeclinationEffect of Declination
N S
E
W
P

Calculating Sunrise/setCalculating Sunrise/set
 Obtain times at specified latitudes fromObtain times at specified latitudes from
Nautical Almanac.Nautical Almanac.
 Interpolate times for the correct latitude.Interpolate times for the correct latitude.
 If not middle day, check for tri-daily changeIf not middle day, check for tri-daily change
(previous or following page).(previous or following page).
 Apply correction for Arc to Time (longitude).Apply correction for Arc to Time (longitude).
 Convert time to event from Z to zone time.Convert time to event from Z to zone time.

Nautical Almanac EntryNautical Almanac Entry
Morning
Twilights
Sunrise
Sunset
Evening
Twilights
Tabulated
Latitudes
Dates 3 Day Period

Extract from NAExtract from NA
Twilight Moonrise
Lat Naut Civil Sunrise 22 23 24 25
h m h m h m h m h m h m h m
N 72 05 29 06 49 08 05 19 01 20 50 22 31 24 08
N 70 05 29 06 41 07 48 19 55 21 23 22 53 24 22
68 05 29 06 34 07 34 20 28 21 48 23 10 24 33
66 05 28 06 29 07 23 20 52 22 06 23 24 24 42
64 05 28 06 24 07 14 21 10 22 21 23 35 24 50
62 05 28 06 20 07 06 21 26 22 34 23 45 24 57
60 05 27 06 16 06 59 21 38 22 44 23 53 25 02
N 58 05 27 06 12 06 53 21 49 22 54 24 00 00 00
56 05 26 06 09 06 48 21 59 23 02 24 06 00 06
54 05 25 06 07 06 43 22 07 23 09 24 12 00 12
52 05 25 06 04 06 39 22 15 23 15 24 17 00 17
50 05 24 06 02 06 35 22 22 23 21 24 22 00 22
45 05 22 05 56 06 26 22 36 23 34 24 32 00 32
N 40 05 20 05 51 06 19 22 48 23 44 24 40 00 40
35 05 17 05 47 06 13 22 58 23 53 24 47 00 47
30 05 15 05 43 06 07 23 07 24 00 00 00 00 53
20 05 09 05 35 05 58 23 23 24 14 00 14 01 04
N 10 05 03 05 28 05 49 23 36 24 25 00 25 01 13
0 04 55 05 20 05 41 23 49 24 36 00 36 01 22
S 10 04 46 05 11 05 33 24 01 00 01 00 47 01 31
20 04 35 05 01 05 24 24 14 00 14 00 59 01 40
30 04 20 04 49 05 14 24 30 00 30 01 12 01 51
35 04 10 04 41 05 08 24 39 00 39 01 20 01 57
40 03 58 04 32 05 01 00 04 00 49 01 28 02 04
45 03 44 04 22 04 53 00 17 01 01 01 38 02 12
S 50 03 25 04 09 04 43 00 33 01 15 01 51 02 21
52 03 16 04 02 04 39 00 40 01 22 01 56 02 26
54 03 06 03 55 04 34 00 49 01 29 02 03 02 31
56 02 54 03 47 04 28 00 58 01 37 02 09 02 36
58 02 39 03 38 04 22 01 08 01 47 02 17 02 42
S 60 02 22 03 28 04 15 01 20 01 57 02 26 02 49

Calculation SheetCalculation Sheet
Port.................................. Date.........................................
DR Lat............................. DR Long.............................. Zone........
TIMES
Higher
Latitude
Difference
Tabular
Interval
Daily Change
Lower
Latitude
Latitude Increment Time Diff
Daily Change/Long Corrn Apply correction to SR/SS and
twilights if date is not the middle day
Local Mean Time (LMT) Longitude Correction from Table II is
only applied to MR/MS
Arc to Time (Longitude)
Universal Time (UT/GMT)
Zone ( ) (Change the sign)
ZONE TIME

Sunset ExampleSunset Example
 Date 5 Feb 1997Date 5 Feb 1997
 DR Position 48DR Position 48oo
30’N 02230’N 022oo
20’W20’W
 Zone Time (+1)Zone Time (+1)
 5050oo
NN 16591659
 4545oo
NN 17121712

Rising/SettingRising/Setting
Port……..……… Date…………..
DR Lat…..….. DR Long…….... Zone....
Higher Lat.
Lower Lat.
Latitude Increment
Daily Change/Long Corrn
Local Mean Time (LMT)
Zone ( )(Change sign)
Zone Time
Diff.
Daily Change
Time Diff.
5 Feb 87
48o
30N 22o
20W +1
50o
N
45o
N
1659
1712
-13

Table 1 - LatitudeTable 1 - Latitude
TABLES FOR INTERPOLATING SUNRISE, MOONRISE, ETC.
TABLE 1-FOR LATITUDE
Tabular Interval Difference between the times for consecutive latitudes
10° 5° 2° 5m
10m
15m
20m
25m
30m
35m
40m
45m
50m
55m
60m
1h
05m
1h
10m
1h
15m
1h
20m
°‘ °‘ °‘ m m m m m m m m m m m m h m h m h m h m
0 30 0 15 0 06 0 0 1 1 1 1 1 2 2 2 2 2 0 02 0 02 0 02 0 02
1 00 0 30 0 12 0 1 1 2 2 3 3 3 4 4 4 5 05 05 05 05
1 30 0 45 0 18 1 1 2 3 3 4 4 5 5 6 7 7 07 07 07 07
2 00 1 00 0 24 1 2 3 4 5 5 6 7 7 8 9 10 10 10 10 10
2 30 1 15 0 30 1 2 4 5 6 7 8 9 9 10 11 12 12 13 13 13
3 00 1 30 0 36 1 3 4 6 7 8 9 10 11 12 13 14 0 15 0 15 0 16 0 16
3 30 1 45 0 42 2 3 5 7 8 10 11 12 13 14 16 17 18 18 19 19
4 00 2 00 0 48 2 4 6 8 9 11 13 14 15 16 18 19 20 21 22 22
4 30 2 15 0 54 2 4 7 9 11 13 15 16 18 19 21 22 23 24 25 26
5 00 2 30 1 00 2 5 7 10 12 14 16 18 20 22 23 25 26 27 28 29
5 30 2 45 1 06 3 5 8 11 13 16 18 20 22 24 26 28 0 29 0 30 0 31 0 32
6 00 3 00 1 12 3 6 9 12 14 17 20 22 24 26 29 31 32 33 34 36
6 30 3 15 1 18 3 6 10 13 16 19 22 24 26 29 31 34 36 37 38 40
7 00 3 30 1 24 3 7 10 14 17 20 23 26 29 31 34 37 39 41 42 44
7 30 3 45 1 30 4 7 11 15 18 22 25 28 31 34 37 40 43 44 46 48
8 00 4 00 1 36 4 8 12 16 20 23 27 30 34 37 41 44 0 47 0 48 0 51 0 53
8 30 4 15 1 42 4 8 13 17 21 25 29 33 36 40 44 48 0 51 0 53 0 56 0 58
9 00 4 30 1 48 4 9 13 18 22 27 31 35 39 43 47 52 0 55 0 58 1 01 1 04
9 30 4 45 1 54 5 9 14 19 24 28 33 38 42 47 51 56 1 00 1 04 1 08 1 12
10 00 5 00 2 00 5 10 15 20 25 30 35 40 45 50 55 60 1 05 1 10 1 15 1 20

Port……..……… Date…………..
Higher Lat.
Lower Lat.
Latitude Increment
Zone Time
Diff.
Daily Change
Time Diff.
5 Feb 87
48o
30N 22o
20W +1
50o
N
45o
N
1659
1712
-13
-0009 1716 +4/3
+0001
1704

Arc to TimeArc to Time
CONVERSION OF ARC TO TIME
0°-59° 60°-119°120°-179°180°-239°240°-299°300°-359° 0 00 0 25 0 50 0 75
h m h m h m h m h m h m m s m s m s m s
0 0 00 60 4 00 120 8 00 180 12 00 240 16 00 300 20 00 0 0 00 0 01 0 02 0 03
1 0 04 61 4 04 121 8 04 181 12 04 241 16 04 301 20 04 1 0 04 0 05 0 06 0 07
2 0 08 62 4 08 122 8 08 182 12 08 242 16 08 302 20 08 2 0 08 0 09 0 10 0 11
3 0 12 63 4 12 123 8 12 183 12 12 243 16 12 303 20 12 3 0 12 0 13 0 14 0 15
4 0 16 64 4 16 124 8 16 184 12 16 244 16 16 304 20 16 4 0 16 0 17 0 18 0 19
5 0 20 65 4 20 125 8 20 185 12 20 245 16 20 305 20 20 5 0 20 0 21 0 22 0 23
6 0 24 66 4 24 126 8 24 186 12 24 246 16 24 306 20 24 6 0 24 0 25 0 26 0 27
7 0 28 67 4 28 127 8 28 187 12 28 247 16 28 307 20 28 7 0 28 0 29 0 30 0 31
8 0 32 68 4 32 128 8 32 188 12 32 248 16 32 308 20 32 8 0 32 0 33 0 34 0 35
9 0 36 69 4 36 129 8 36 189 12 36 249 16 36 309 20 36 9 0 36 0 37 0 38 0 39
10 0 40 70 4 40 130 8 40 190 12 40 250 16 40 310 20 40 10 0 40 0 41 0 42 0 43
11 0 44 71 4 44 131 8 44 191 12 44 251 16 44 311 20 44 11 0 44 0 45 0 46 0 47
12 0 48 72 4 48 132 8 48 192 12 48 252 16 48 312 20 48 12 0 48 0 49 0 50 0 51
13 0 52 73 4 52 133 8 52 193 12 52 253 16 52 313 20 52 13 0 52 0 53 0 54 0 55
14 0 56 74 4 56 134 8 56 194 12 56 254 16 56 314 2056 14 0 56 0 57 0 58 0 59
15 1 00 75 5 00 135 9 00 195 13 00 255 17 00 315 21 00 15 1 00 1 01 1 02 1 03
16 1 04 76 5 04 136 9 04 196 13 04 256 17 04 316 21 04 16 1 04 1 05 1 06 1 07
17 1 08 77 5 08 137 9 08 197 13 08 257 17 08 317 21 08 17 1 08 1 09 1 10 1 11
18 1 12 78 5 12 138 9 12 198 13 12 258 17 12 318 21 12 18 1 12 1 13 1 14 1 15
19 1 16 79 5 16 139 9 16 199 13 16 259 17 16 319 21 16 19 1 16 1 17 1 18 1 19
20 1 20 80 5 20 140 9 20 200 13 20 260 17 20 320 21 20 20 1 20 1 21 1 22 1 23
21 1 24 81 5 24 141 9 24 201 13 24 261 17 24 321 21 24 21 1 24 1 25 1 26 1 26
22 1 28 82 5 28 142 9 28 202 13 28 262 17 28 322 21 28 22 1 28 1 29 1 30 1 31

Port……..……… Date…………..
Higher Lat.
Lower Lat.
Latitude Increment
Zone Time
Diff.
Daily Change
Time Diff.
5 Feb 87
48o
30N 22o
20W +1
50o
N
45o
N
1659
1712
-13
-0009 1716 +4/3
+0001
1704
+0129
1833
-0100
1733

TwilightTwilight
 At the times given for the beginning and end ofAt the times given for the beginning and end of
twilight, the Sun’s zenith distance is 96twilight, the Sun’s zenith distance is 96oo
for civil,for civil,
and 102and 102oo
for nautical twilight.for nautical twilight.
 The degree of illumination at the times given forThe degree of illumination at the times given for
civil twilight is such that the brightest stars arecivil twilight is such that the brightest stars are
visible and the horizon is clearly defined.visible and the horizon is clearly defined.
 At the times given for nautical twilight, theAt the times given for nautical twilight, the
horizon is in general not visible.horizon is in general not visible.
 Nautical AlmanacNautical Almanac

Twilight ExplainedTwilight Explained
Celestial Horizon
Zenith
Civil Twilight
96o
Nautical Twilight
102o

Twilight ExampleTwilight Example
 What time will Evening CivilWhat time will Evening Civil
Twilight (ECT) occur on 22Twilight (ECT) occur on 22ndnd
October 1997 in position 33October 1997 in position 33oo
20’S 04220’S 042oo
45’E? Give your45’E? Give your
answer in Zone Time (-3).answer in Zone Time (-3).

Twilight ExampleTwilight Example
Port……..……… Date…………..
Higher Lat.
Lower Lat.
Latitude Increment
Zone Time
Diff.
Daily Change
Time Diff.
22 Oct 87
33o
20S 42o
45E -3
35o
S
30o
S
1848
1840
+8
+0005 1838 -2/3
-0001
1844
-0251
1553
+0300
1853

Moonrise/MoonsetMoonrise/Moonset
 The times of Moonrise and MoonsetThe times of Moonrise and Moonset
generally become later each day by aboutgenerally become later each day by about
50 minutes.50 minutes.
 The “lunar day” is therefore roughly 25The “lunar day” is therefore roughly 25
hours and the angular movement of thehours and the angular movement of the
Moon would be about 360/25 = 14.4Moon would be about 360/25 = 14.4oo
perper
hour.hour.
 Using arc to time of 15Using arc to time of 15oo
per hour is notper hour is not
accurate but an allowance can be madeaccurate but an allowance can be made
called the longitude correction.called the longitude correction.

NauticalNautical
AlmanacAlmanac
MR/MSMR/MS
Moonrise
Moonset

Table II - for LongitudeTable II - for Longitude
TABLE II-FOR LONGITUDE
Difference between the times for given date and preceding date (for east longitude)
or for given date and following date (for west longitude)
1h+ 1h+
Long
East or
West
10m
20m
30m
40m
50m
60m
10m
20m
30m
40m
50m
60m
2h
10m
2h
20m
2h
30m
2h
40m
2h
50m
3h
00m
°m m m m m m m m m m m m h m h m h m h m h m h m
0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 0 00 0 00 0 00 0 00 0 00
10 0 1 1 1 1 2 2 2 2 3 3 3 04 04 04 04 05 05
20 1 1 2 2 3 3 4 4 5 6 6 7 07 08 08 09 09 10
30 1 2 2 3 4 5 6 7 7 8 9 10 11 12 12 13 14 15
40 1 2 3 4 6 7 8 9 10 11 12 13 14 16 17 18 19 20
50 1 3 4 6 7 8 10 11 12 14 15 17 0 18 0 19 0 21 0 22 0 24 0 25
60 2 3 5 7 8 10 12 13 15 17 18 20 22 23 25 27 28 30
70 2 4 6 8 10 12 14 16 17 19 21 23 25 27 29 31 33 35
80 2 4 7 9 11 13 16 18 20 22 24 27 29 31 33 36 38 40
90 2 5 7 10 12 15 17 20 22 25 27 30 32 35 37 40 42 45
100 3 6 8 11 14 17 19 22 25 28 31 33 0 36 0 39 0 42 0 44 0 47 0 50
110 3 6 9 12 15 18 21 24 27 31 34 37 40 43 46 49 52 0 55
120 3 7 10 13 17 20 23 27 30 33 37 40 43 47 50 53 57 1 00
130 4 7 11 14 18 22 25 29 32 36 40 43 47 51 54 0 58 1 01 1 05
140 4 8 12 16 19 23 27 31 35 39 43 47 51 54 0 58 1 02 1 06 1 10
150 4 8 13 17 21 25 29 33 38 42 46 50 0 54 0 58 1 03 1 07 1 11 1 15
160 4 9 13 18 22 27 31 36 40 44 49 53 0 58 1 02 1 07 1 11 1 16 1 20
170 5 9 14 19 24 28 33 38 42 47 52 57 1 01 1 06 1 11 1 16 1 20 1 25
180 5 10 15 20 25 30 35 40 45 50 55 60 1 05 1 10 1 15 1 20 1 25 1 30

Moonrise ExampleMoonrise Example
(Halifax, Nova Scotia)(Halifax, Nova Scotia)
 What is the legal time ofWhat is the legal time of
moonrise on 17moonrise on 17thth
June inJune in
Halifax, Nova Scotia?Halifax, Nova Scotia?
 From Nories Tables:From Nories Tables:
 Halifax 44Halifax 44oo
40’N 06340’N 063oo
34’W34’W

Moonrise/MoonsetMoonrise/Moonset
Port…………… Date…………..
DR Lat…….. DR Long…….... Zone....
Higher Lat.
Lower Lat.
Latitude Increment
Zone Time
Diff.
Daily Change
Time Diff.
HALIFAX 17 Jun 97
44o
40’N 63o
34’W +3
45o
N
40o
N
1614
1605
+09
+08 1706 +61min
+11
1624
+0414
2038
+3 -0300
1738

Example (Wuhu)Example (Wuhu)
 What are the legal timesWhat are the legal times
of sunset and moonset atof sunset and moonset at
Wuhu, Yangtse River, onWuhu, Yangtse River, on
2222ndnd
October?October?
 From Nories Tables:From Nories Tables:
 Wuhu 31Wuhu 31oo
20’N 11820’N 118oo
21’E21’E

Sunset at WuhuSunset at Wuhu
Port……..……… Date…………..
Higher Lat.
Lower Lat.
Latitude Increment
Zone Time
Diff.
Daily Change
Time Diff.
22 Oct 87
31o
20N 118o
21E -8
35o
N
30o
N
1715
1721
-6
-0001 1724 +3/3
+0001
1721
-0753
0928
+0800
1728

Moonset at WuhuMoonset at Wuhu
Port……..……… Date…………..
Higher Lat.
Lower Lat.
Latitude Increment
Zone Time
Diff.
Daily Change
Time Diff.
22 Oct 87
31o
20N 118o
21E -8
35o
N
30o
N
1215
1206
+9
+0002 1117 -49
-0016
1152
-0753
0359
+0800
1159

Gyro ChecksGyro Checks
 Checking the gyro at sunrise/sunset is:Checking the gyro at sunrise/sunset is:
 Accurate because the sun is on theAccurate because the sun is on the
horizonhorizon
 Easy to check usingEasy to check using True Amplitudes.True Amplitudes.
 Bearing is taken when the lower limbBearing is taken when the lower limb
appears to lie a semi diameter above theappears to lie a semi diameter above the
horizon.horizon.
 The amplitude table is entered with ship’sThe amplitude table is entered with ship’s
latitude and the declination of the Sun.latitude and the declination of the Sun.

True and Visible Rise/setTrue and Visible Rise/set
Celestial Horizon
Visible Horizon
Visible Sunrise
Sunset
True Sunrise
Sunset
Civil Twilight
6 deg
34’

Celestial SphereCelestial Sphere
Horizon
Equator
Pole
Zenith

Path of the SunPath of the Sun
North
Equator
Pole
South
West
East

AmplitudeAmplitude
North
Equator
Pole
South
West
East

Amplitude (Dec opposite)Amplitude (Dec opposite)
North
Equator
Pole
South
West
East

Elements of CalculationElements of Calculation
 Convert time to GMTConvert time to GMT
 Work out declination of the sunWork out declination of the sun
rounding up/down to the nearestrounding up/down to the nearest
hour.hour.
 Note latitude (given in theNote latitude (given in the
question)question)
 Find true amplitude using tableFind true amplitude using table
 Apply amplitude to East/West inApply amplitude to East/West in
direction of declination.direction of declination.

ExampleExample
 At about 2000(-11) 0n 15 Jun 97, inAt about 2000(-11) 0n 15 Jun 97, in
DR position 48º 50’N, 164º 30’E,DR position 48º 50’N, 164º 30’E,
the sun bore 309º when the lowerthe sun bore 309º when the lower
limb was one semi-diameter abovelimb was one semi-diameter above
the visible horizon. What was thethe visible horizon. What was the
gyro error?gyro error?

Sun’sSun’s
DeclinationDeclination
Sun’s
Declination
Sun’s SD and
“d” correction
Hourly GMT
over three
day period

Example (Working)Example (Working)
 Time:Time: 152000(-11) JUN152000(-11) JUN
 GMT:GMT: 150900Z JUN150900Z JUN
 Dec:Dec: N23N23oo
18.9’ or 23.318.9’ or 23.3oo
 Lat:Lat: 4848oo
50’N or 48.8º50’N or 48.8º

AmplitudeAmplitude
Table pageTable page
4B-174B-17
Declination
Latitude

Example (Working)Example (Working)
 Time:Time: 152000(-11) JUN152000(-11) JUN
 GMT:GMT: 150900Z JUN150900Z JUN
 Dec:Dec: N23N23oo
18.9’ or 23.318.9’ or 23.3oo
(page(page
4A-19)4A-19)
 Lat:Lat: 4848oo
50’N or 48.8º50’N or 48.8º
 Amp:Amp: W 37W 37oo
NN
 Bearing:Bearing: 270270oo
+ 37+ 37oo
= 307= 307oo
 Error:Error: 309309oo
G/307G/307oo
T = 2T = 2oo
HIGHHIGH

Amplitude DiagramAmplitude Diagram
Declination
North
Declination
South
N
S
EW
- ve
+ve
+ve
- ve

FormulaFormula
Sine DeclinationSine Amplitude =
Cosine Latitude

Any Questions?Any Questions?

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