Ephemeral lrg

Grunt Productions 2007

Time, Rise/Set and Time, Rise/Set and Gyro ChecksGyro Checks

Using data in the Nautical Using data in the Nautical AlmanacAlmanac

A brief by Lance GrindleyA brief by Lance Grindley


CoveringCovering

Time and time zones including Time and time zones including questions on passage planning.questions on passage planning.

Rising and setting, twilights and Rising and setting, twilights and Moonrise or MoonsetMoonrise or Moonset

Gyro checks at Sunrise or Sunset Gyro checks at Sunrise or Sunset using the True Amplitude Tables using the True Amplitude Tables (Nories)(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 = in 24 hours = 1515oo per hour. per hour.

The Sun moves through 15The Sun moves through 15oo of of longitude every hour - called Arc to longitude every hour - called Arc to Time.Time.

Used as a basic division of Used as a basic division of Standard Time Zones which are Standard Time Zones which are divided into areas 15° in longitude divided into areas 15° in longitude across.across.


Uniform Time SystemUniform Time System Conceived to ensure all vessels at sea Conceived to ensure all vessels at sea

within same area are keeping the within same area are keeping the same zone timesame zone time

Based on Solar Day 360Based on Solar Day 360oo in 24 hours in 24 hours gives 15gives 15oo per hour per hour

Zones are described in ALRS Vol. 2 Zones are described in ALRS Vol. 2 page 255page 255

Ships may not necessarily keep to Ships may not necessarily keep to these Standard Time Zonesthese Standard Time Zones


Standard Time ZonesStandard Time Zones


Time Zone Time Zone ConventionsConventions

Time zones usually designated Time zones usually designated numerically by indicating correction numerically by indicating correction to zone time to obtain GMTto zone time to obtain GMT

Easterly zones negative, westerly Easterly zones negative, westerly zones positivezones positive

May be indicated by letter Z for May be indicated by letter Z for GMT, A to M increasing easterly GMT, A to M increasing easterly (omitting J), N to Y increasing (omitting J), N to Y increasing westerlywesterly


Standard Time Zones (1)Standard Time Zones (1)Greenwich

71/2oW 71/2

oE 221/2oE 371/2

oE221/2oW371/2

oW

12001100100009000800

(-2)B

(-1)A

(0)Z

(+1)N

(+2)O



71/2oW 71/2

oE 221/2oE 371/2

oE221/2oW371/2

oW

13001200110010000900

(-2)B

(-1)A

(0)Z

(+1)N

(+2)O



71/2oW 71/2

oE 221/2oE 371/2

oE221/2oW371/2

oW

14001300120011001000

(-2)B

(-1)A

(0)Z

(+1)N

(+2)O



71/2oW 71/2

oE 221/2oE 371/2

oE221/2oW371/2

oW

15001400130012001100

(-2)B

(-1)A

(0)Z

(+1)N

(+2)O



71/2oW 71/2

oE 221/2oE 371/2

oE221/2oW371/2

oW

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 Universal Time (UT1) is the Mean Solar Time of the prime meridian obtained by Time of the prime meridian obtained by direct astronomical observationdirect astronomical observation

Greenwich Mean Time generally equivalent Greenwich Mean Time generally equivalent to UT1 and used to define angular position to UT1 and used to define angular position relative to the prime meridianrelative to the prime meridian

International Atomic Time (TA1) based on International Atomic Time (TA1) based on Cesium clock - very accurate but not Cesium clock - very accurate but not corrected for polar variation - hence leap corrected 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 May not conform to the longitude as

legal time is adjusted for political and legal time is adjusted for political and commercial reasons.commercial reasons.

Many countries employ daylight saving Many countries employ daylight saving time (DST) when clocks are advanced by time (DST) when clocks are advanced by one hour.one hour.

Dates for DST must be checked in the Dates 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 This gives total time period of the

passagepassage 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 NB Legal to Zulu follow sign - Zulu to

Legal reverse the sign Legal reverse the sign


Example Example

D14. Your ship is leaving D14. Your ship is leaving WELLINGTON (New Zealand) at 1000 WELLINGTON (New Zealand) at 1000 local time on 7 Feb 98, bound for local time on 7 Feb 98, bound for PANAMA, a distance of 6,480 nautical PANAMA, a distance of 6,480 nautical miles. Allowing a passage speed of miles. Allowing a passage speed of 12 knots, and allowing a zero TIH for 12 knots, and allowing a zero TIH for one hour per day or part of a day, one hour per day or part of a day, also allow 8 hours for refuelling at also allow 8 hours for refuelling at sea, what is your ETA?sea, 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 Panama ETA Panama 021100(+5)021100(+5)


Changing Time ZonesChanging Time Zones

A ship keeping the Standard Time Zone for A ship keeping the Standard Time Zone for 6060oo West is due to arrive at PARAMARIBO West 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 hours Move from 4 hours behind GMT to 3 hours

behind GMT, therefore clocks behind GMT, therefore clocks advanced by advanced 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-sunset 16’ is allowed for semi-diameter and 34’ for horizontal diameter and 34’ for horizontal refraction, so that at the times given refraction, so that at the times given the Sun’s upper limb is on the visible the Sun’s upper limb is on the visible horizon; all time refer to the horizon; all time refer to the phenomena as seen from sea level phenomena as seen from sea level with a clear horizon.with a 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 from Obtain 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 If not middle day, check for tri-daily

change (previous or following page).change (previous or following page). Apply correction for Arc to Time Apply correction for Arc to Time

(longitude).(longitude). Convert time to event from Z to zone Convert time to event from Z to zone

time. time.


Nautical Almanac Nautical Almanac EntryEntry

Morning Twilights Sunrise

Sunset Evening Twilights

Tabulated Latitudes

Dates 3 Day Period


Extract from NA Extract from NA Twilight Moonrise

Lat Naut Civil Sunrise 22 23 24 25h 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 04N 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 42S 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........

TIMESHigherLatitude

DifferenceTabularInterval

Daily ChangeLowerLatitudeLatitude Increment Time Diff

Daily Change/Long Corrn Apply correction to SR/SS andtwilights if date is not the middle day

Local Mean Time (LMT) Longitude Correction from Table II isonly 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 022 30’N 022oo 20’W 20’W Zone Time (+1)Zone Time (+1) 5050ooNN 16591659 4545ooNN 17121712


Rising/SettingRising/SettingPort……..……… 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 8748o30N 22o20W +1

50oN

45oN

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 latitudes10 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 m0 30 0 15 0 06 0 0 1 1 1 1 1 2 2 2 2 2 0 02 0 02 0 02 0 021 00 0 30 0 12 0 1 1 2 2 3 3 3 4 4 4 5 05 05 05 051 30 0 45 0 18 1 1 2 3 3 4 4 5 5 6 7 7 07 07 07 072 00 1 00 0 24 1 2 3 4 5 5 6 7 7 8 9 10 10 10 10 102 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 0 163 30 1 45 0 42 2 3 5 7 8 10 11 12 13 14 16 17 18 18 19 194 00 2 00 0 48 2 4 6 8 9 11 13 14 15 16 18 19 20 21 22 224 30 2 15 0 54 2 4 7 9 11 13 15 16 18 19 21 22 23 24 25 265 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 0 326 00 3 00 1 12 3 6 9 12 14 17 20 22 24 26 29 31 32 33 34 366 30 3 15 1 18 3 6 10 13 16 19 22 24 26 29 31 34 36 37 38 407 00 3 30 1 24 3 7 10 14 17 20 23 26 29 31 34 37 39 41 42 447 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 0 538 30 4 15 1 42 4 8 13 17 21 25 29 33 36 40 44 48 0 51 0 53 0 56 0 589 00 4 30 1 48 4 9 13 18 22 27 31 35 39 43 47 52 0 55 0 58 1 01 1 049 30 4 45 1 54 5 9 14 19 24 28 33 38 42 47 51 56 1 00 1 04 1 08 1 1210 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



Higher Lat.

Lower Lat.

Latitude Increment






Zone Time

Diff.

Daily Change

Time Diff.

5 Feb 8748o30N 22o20W +1

50oN

45oN

1659

1712-13

-0009 1716 +4/3

+0001

1704


Arc to Time Arc to Time

CONVERSION OF ARC TO TIME0 -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 s0 0 00 60 4 00 120 8 00 180 12 00 240 16 00 300 20 00 0 0 00 0 01 0 02 0 031 0 04 61 4 04 121 8 04 181 12 04 241 16 04 301 20 04 1 0 04 0 05 0 06 0 072 0 08 62 4 08 122 8 08 182 12 08 242 16 08 302 20 08 2 0 08 0 09 0 10 0 113 0 12 63 4 12 123 8 12 183 12 12 243 16 12 303 20 12 3 0 12 0 13 0 14 0 154 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 0 236 0 24 66 4 24 126 8 24 186 12 24 246 16 24 306 20 24 6 0 24 0 25 0 26 0 277 0 28 67 4 28 127 8 28 187 12 28 247 16 28 307 20 28 7 0 28 0 29 0 30 0 318 0 32 68 4 32 128 8 32 188 12 32 248 16 32 308 20 32 8 0 32 0 33 0 34 0 359 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 4311 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 4712 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 5113 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 5514 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 0316 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 0717 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 1118 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 1519 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 2321 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 2622 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



Higher Lat.

Lower Lat.

Latitude Increment






Zone Time

Diff.

Daily Change

Time Diff.

5 Feb 8748o30N 22o20W +1

50oN

45oN

1659

1712-13

-0009 1716 +4/3

+0001

1704

+0129

1833

-0100

1733


TwilightTwilight

At the times given for the beginning and At the times given for the beginning and end of twilight, the Sun’s zenith distance is end of twilight, the Sun’s zenith distance is 9696oo for civil, and 102 for civil, and 102oo for nautical twilight. for nautical twilight.

The degree of illumination at the times The degree of illumination at the times given for civil twilight is such that the given for civil twilight is such that the brightest stars are visible and the horizon brightest stars are visible and the horizon is clearly defined.is clearly defined.

At the times given for nautical twilight, the At 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 Civil What time will Evening Civil Twilight (ECT) occur on 22Twilight (ECT) occur on 22ndnd October 1997 in position October 1997 in position 3333oo 20’S 042 20’S 042oo 45’E? Give 45’E? Give your answer in Zone Time your answer in Zone Time (-3).(-3).


Twilight ExampleTwilight ExamplePort……..……… Date…………..DR Lat…..….. DR Long…….... Zone....

Higher Lat.

Lower Lat.

Latitude Increment






Zone Time

Diff.

Daily Change

Time Diff.

22 Oct 8733o20S 42o45E -3

35oS

30oS

1848

1840+8

+0005 1838 -2/3

-0001

1844

-0251

1553

+0300

1853


Moonrise/MoonsetMoonrise/Moonset The times of Moonrise and Moonset generally The times of Moonrise and Moonset generally

become later each day by about 50 minutes.become later each day by about 50 minutes. The “lunar day” is therefore roughly 25 hours The “lunar day” is therefore roughly 25 hours

and the angular movement of the Moon would and the angular movement of the Moon would be about 360/25 = 14.4be about 360/25 = 14.4oo per hour. per hour.

Using arc to time of 15Using arc to time of 15oo per hour is not per hour is not accurate but an allowance can be made called accurate but an allowance can be made called the longitude correction.the longitude correction.


Nautical Nautical Almanac Almanac MR/MSMR/MS

Moonrise

Moonset


Table II - for LongitudeTable II - for Longitude

TABLE II-FOR LONGITUDEDifference between the times for given date and preceding date (for east longitude)

or for given date and following date (for west longitude)1h+ 1h+

LongEast orWest

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 m0 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 0520 1 1 2 2 3 3 4 4 5 6 6 7 07 08 08 09 09 1030 1 2 2 3 4 5 6 7 7 8 9 10 11 12 12 13 14 1540 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 2560 2 3 5 7 8 10 12 13 15 17 18 20 22 23 25 27 28 3070 2 4 6 8 10 12 14 16 17 19 21 23 25 27 29 31 33 3580 2 4 7 9 11 13 16 18 20 22 24 27 29 31 33 36 38 4090 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 50110 3 6 9 12 15 18 21 24 27 31 34 37 40 43 46 49 52 0 55120 3 7 10 13 17 20 23 27 30 33 37 40 43 47 50 53 57 1 00130 4 7 11 14 18 22 25 29 32 36 40 43 47 51 54 0 58 1 01 1 05140 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 15160 4 9 13 18 22 27 31 36 40 44 49 53 0 58 1 02 1 07 1 11 1 16 1 20170 5 9 14 19 24 28 33 38 42 47 52 57 1 01 1 06 1 11 1 16 1 20 1 25180 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 Example Moonrise Example (Halifax, Nova Scotia)(Halifax, Nova Scotia)

What is the legal time of What is the legal time of moonrise on 17moonrise on 17thth June in June in Halifax, Nova Scotia?Halifax, Nova Scotia?

From Nories Tables:From Nories Tables: Halifax 44Halifax 44oo 40’N 063 40’N 063oo

34’W 34’W


Moonrise/MoonsetMoonrise/MoonsetPort…………… 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

45oN

40oN

1614

1605

+09

+08 1706 +61min

+11

1624

+0414

2038

+3 -0300

1738


Example (Wuhu)Example (Wuhu)

What are the legal times What are the legal times of sunset and moonset of sunset and moonset at Wuhu, Yangtse River, at Wuhu, Yangtse River, on 22on 22ndnd October? October?

From Nories Tables:From Nories Tables: Wuhu 31Wuhu 31oo 20’N 118 20’N 118oo 21’E 21’E


Sunset at WuhuSunset at WuhuPort……..……… Date…………..DR Lat…..….. DR Long…….... Zone....

Higher Lat.

Lower Lat.

Latitude Increment






Zone Time

Diff.

Daily Change

Time Diff.

22 Oct 8731o20N 118o21E -8

35oN

30oN

1715

1721-6

-0001 1724 +3/3

+0001

1721

-0753

0928

+0800

1728


Moonset at WuhuMoonset at WuhuPort……..……… Date…………..DR Lat…..….. DR Long…….... Zone....

Higher Lat.

Lower Lat.

Latitude Increment






Zone Time

Diff.

Daily Change

Time Diff.

22 Oct 8731o20N 118o21E -8

35oN

30oN

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 the Accurate because the sun is on the

horizonhorizon Easy to check using Easy to check using True Amplitudes.True Amplitudes. Bearing is taken when the lower limb Bearing is taken when the lower limb

appears to lie a semi diameter above the appears to lie a semi diameter above the horizon.horizon.

The amplitude table is entered with ship’s The amplitude table is entered with ship’s latitude and the declination of the Sun.latitude and the declination of the Sun.


True and Visible True and Visible Rise/set Rise/set

Celestial Horizon

Visible Horizon

Visible SunriseSunset

True SunriseSunset

Civil Twilight

6 deg

34’


Celestial SphereCelestial Sphere

Horizon

EquatorPole

Zenith


Path of the SunPath of the Sun

North

EquatorPole

South

West

East


AmplitudeAmplitude

North

EquatorPole

South

West

East


Amplitude (Dec Amplitude (Dec opposite)opposite)

North

EquatorPole

South

West

East


Elements of CalculationElements of Calculation Convert time to GMTConvert time to GMT Work out declination of the sun Work out declination of the sun

rounding up/down to the nearest rounding up/down to the nearest hour.hour.

Note latitude (given in the Note latitude (given in the question)question)

Find true amplitude using tableFind true amplitude using table Apply amplitude to East/West in Apply amplitude to East/West in

direction of declination.direction of declination.


Example Example

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


Sun’s Sun’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 23.3 18.9’ or 23.3oo

Lat:Lat: 4848oo 50’N or 48.8º 50’N or 48.8º


Amplitude Amplitude Table page Table 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 23.3 18.9’ or 23.3o o

(page 4A-19)(page 4A-19) Lat:Lat: 4848oo 50’N or 48.8º 50’N or 48.8º Amp:Amp: W 37W 37oo N N Bearing:Bearing: 270270oo + 37 + 37oo = 307 = 307oo

Error:Error: 309309ooG/307G/307ooT = 2T = 2oo HIGH HIGH


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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