GYRO ERROR CORRECTION / OBJECT MOON

UTC23h 59m 30sDate07/10/2008

PSNLAT 30 18,4 N

LON014 19,1 WGB238

1. Install the bearing finder on the repeater.

2. Take sun bearing. We got the Gyro Bearing (GB).

3. In fast, write down the UTC (h:m:s) & co-ordinates from GPS.

4. From the NAUTICAL ALMANAC (YEAR) for the voyage date (written in the up of left and right pages (p. 10-253)) find column MOON on the right page in the page base.

By the argument HOUR & DATE (for example: 18h of 20/12/2007) take Greenwich Hour Angle (GHA), Declination (Dec), & d, which are placed in the page bottom.

For Example:GHA : 68 26,3

Dec : 23 46,6 S

d : 7,3

5. From the table Increments and corrections of the same manual (p. ii-xxxi -yellow pages) in the upper part, find the minutes (in our case 59m) & in the same column find seconds (in our case 30s).

On the cross of these values in column SUN/PLANETS Take value INcr (in our case INcr = 14 11,8). This value always should be added to GHA:

(GHA + Incr) = GHAcor = 68 26,3 + 14 11,8 = 82 38,1

6. Then to the GHAcor add or delete a longitude. If longitude value is W, then , else if value is E, then + . We got the Local Hour Angle (LHA).

GHAcor + (+/- LON) = 82 38,1 14 19,1 = 68 19,0

7. In the book SIGHT REDUCTION TABLES (for our example VOL.2 0-40) find the latitude (e.g. LAT = 30). Search the Z (Azimuth) on crossing of LHA & LAT on the Declination table (SAME or CONTRARY name to LAT). Correcting by interpolation the Z.

If LHA < 180 then: 360 Zcor.

If LHA > 180 then: Z = Zcor

The difference between Z and GB (GB Z) will be gyro error.

GYRO ERROR OBJECT SUN

UTC18h 21m 48sDate20/12/2007

PSNLAT 12 20,8 S

LON013 32,8 EGB180

1. Install the bearing finder on the repeater. Pull down light filters.

2. Take sun bearing so that it was not more than 60 above horizon. Got the Gyro Bearing (GB).

3. In fast sequence write down the UTC (h:m:s) & co-ordinates from GPS.

4. From the NAUTICAL ALMANAC (YEAR) for the voyage date (written in the up of left and right pages (p. 10-253)) find column SUN on the right page in the page base.

By the argument HOUR & DATE (for example: 18h of 20/12/2007) take Greenwich Hour Angle (GHA), Declination (Dec) & d, which are placed in the page bottom.

For Example:GHA: 90 36,6

Dec : 23 25,9 S

d : 0,1

5. From the table Increments and corrections of the same manual (p. ii-xxxi -yellow pages) in the upper part, find the minutes (in our case 21m) & in the same column find seconds (in our case 10s).

On the cross of these values in column SUN/PLANETS Take value INcr (in our case INcr = 5 17,5). This value always should be added to GHA:

GHA + INcr = 90 36,6 + 5 17,5 = 95 54,1

After in the right column, for the same value of minutes find value for d => dcor (in our case = 0,1 = 0,0), its always should be added to Dec. After that, find the total value of Dec.

Dec + dcor = 23 25,9 + 0,0 = 23 25,9

6. Then to the GHA&INcr add or delete a longitude. If longitude value is W, then , else if value is E, then + . We got the Local Hour Angle (LHA).

GHA&INcr + LON = 95 54,1 + 13 32,8 = 109 28,9

7. Open the NORIES NAUTICAL TABLES and find the table A & B (p. 380-399). On left is table A, on right side is B.

At first from table A by argument LHA & current LAT, interpolating, find the value of A (in our case A = 0,07 S). Value, which be added to A is depend on sector, where LHA placed. If its among 90-270, then value A has the as same letter (N/S) as LAT. If its among 270-0-90 is opposite.

8. From the table B by the argument LHA & Dec, interpolating, find the value of B (in our case B = 0,46 S)

As for value of B its as same as value of Dec (N/S). Its a constant rule, shown on the left/right side of pages.

9. Algebraically put A & B. We got C (if marks are different, from bigger subtract smaller value and place mark of bigger)

For example:A + B = 0,07 + 0,46 = 0,53 S

10. From the table C of the same manual (p. 410-423) according the values of arguments of C & LAT, interpolating find the value of azimuth (Z)

In our case:

Z = 62,6

11. According the value Z define in which quarter its placed, using next rule:

Marks of N/S always as same as C has (in our case - S)

Marks of W/E depend on position of LHA. If LHA between 0-180 then W, if between 180-360 - E.

In our case:

LHA = 109 28,9;

therefore Z will be in SW part.

12. Find the value of True Bearing (TB)

if the Z placed in I part, Z = TB

if the Z placed in II part, TB = 180 - Z

if the Z placed in III part, TB = 180 + Z

if the Z placed in IV part, Z = 360 - Z

13. Correction find from algebraic difference of TB & GB:

TB GB = GerL = low, if TB > GB;

H = high, if TB < GB;

GYRO ERROR CORRECTION / OBJECT STAR

UTC03h 03m 08sDate09/10/2008

PSNLAT 24 18,2 N

LON016 34,2 WGB122

1. Select star from a celestial map.

2. Find the star on sky.

3. Take bearing of it. Got the Gyro Bearing (GB).

4. In fast, write down the UTC (h:m:s) & co-ordinates from GPS.

5. From a NAUTICAL ALMANAC (YEAR) for the voyage date (written in the up of left and right pages (p. 10-253)) find column ARIES on the left top of the page. By the argument HOUR & DATE (for example: 03h of 09/10/2008) take Greenwich Hour Angle (SHA); Siderial Hour Angle (GHA) & Declination (Dec), they are placed in the right side of page.

For Example:SHA : 68 26,3

GHA : 63 06,5

Dec : 16 43,4 S

6. From the table Increments and corrections of the same manual (p. ii-xxxi -yellow pages) in the upper part, find the minutes (in our case 03m) & in the same column find seconds (in our case 08s). On the cross of these values in column ARIES take value Incr (in our case Incr = 0 47,1). This value always should be added to GHA&SHA:

GHA cor= (SHA + GHA + Incr)

GHA cor= 258 36,8 + 63 06,5 + 0 47,1' = 322 30,4

7. Then to the GHAcor add or subtract a longitude. If longitude has name W, then mark is , else if name is E, then mark is + . We got the Local Hour Angle (LHA).

LHA = GHAcor + ( LON)

LHA = 322 30,4 016 34,2 = 305 56,2

Note: If the LHA > 360, then LHA= LHA-360

8. Open the NORIES NAUTICAL TABLES and find the table A & B (p.380-399). On left is table A, on right side is B. At first from table A by argument LHA & current LAT, interpolating, find the value of A (in our case A = 0,07 S). Value, which will be added to A is depend on sector, where LHA placed. If its among 90-270, then value A has the as same letter (N/S) as LAT. If its among 270-0-90 is opposite.

9. From the table B by the argument LHA & Dec, interpolating, find the value of B (in our case B = 0,46 S). As for value of B its as same as value of Dec (N/S). Its a constant rule, shown on the left/right side of pages.

10. Algebraically put A & B. We got C (if marks are different, from bigger subtract smaller value and place mark of bigger)

For example:A + B = 0,07 + 0,46 = 0,53 S

The difference between Z and GB (GB Z) will be gyro error.

OBSERVATION LINE _______________________

UTC*DATE:BODY:

+Tsec

UTCGHA*=

+^min sec=

V= +^v= SHA (for stars)

GHA=Dec* =

+E-WLONG= ^d= d=

LHA= Dec=B=

LAT=A=

C=

Az= TB=

-CB=

COURSE= CE=

1.A-Named opposite to Latitude, exept when Hour Angle is between 90&270 degrees.

2.B-Always named the same is Declination .

3.Azimuth takes combined names of C correction and Hour angle.

Sin(Hc) = Sin(LAT) * Sin(Dec) + Cos(LAT) * Cos(Dec) * Cos(LHA)

1. Function of LAT always +.

2. Function of Dec + when is named as LAT;

Sin(Dec) - and Cos(Dec) + when name of Dec opposite to LAT.

3. Cos(LHA) + when LHA< 90 deg.;

Cos(LHA) - when LHA > 90 deg..

LAT =Log Sin =

Dec =Log Sin =

Log Hav=Nat Hav =

LAT =Log Cos=

Dec =Log Cos=

LHA= Log Cos=

Log Hav=Nat Hav =

Nat Hav =

Hc =Log Sin(Hc)=

TIMEHs

Hs =Sextant altitude

i =i=360-oi (lower limb + / upper limb -)

I =Sextant index errorBox of sextant

D =Dip of horizonNT p.453 / Almanac A2

R =Atmospheric refractionNT p.454

PA =Parallax in altitude of the Sun, Moon, Venus or MarsNT p.453

S =Semi-diameter of the Sun or MoonNT p.453 / Almanac daily pgs.

^t,^b=Additional refraction correctionsNT p.454 / Almanac A4

Ho =OBSERVED ALTITUDE

-Hc =CALCULATED ALTITUDE

^H =

Az =

Obtaining the True Altitude

The altitude of the heavenly body (e.g. sun) from the observer's true position is measured using a sextant. This is called the sextant altitude, and has to undergo several corrections before the true altitude can be obtainedThe sextant utilises two mirrors. With this sextant, one of the mirrors ( mirror A in the diagram) is half-silvered, which allows some light to pass through. In navigating, you look at the horizon through this mirror. Other sextants are operated by aligning marked line on the mirrored surface to the horizon, which is visible from the side of the mirror.

The other mirror (mirror B in the diagram) is attached to a movable arm. Light from an object, normally taken to be the sun, reflects off this mirror. The arm can be adjusted to a position where the sun's reflection off the mirror also reflects off mirror A and through the eyepiece.Looking through the eyepiece, the moving arm is adjusted such that the object appears to rest on the horizon. When this happens, one object (the sun) is superimposed on the other (the horizon). The angle between the two objects is then read off the scale. An angle in degrees can be read off the sextant and used to calculate lunar distance, longitude and location on the Earth.

What makes a sextant so useful in navigation is its accuracy. It can measure an angle with precision to the nearest ten seconds. (A degree is divided into 60 minutes.)1. Index Error

This is the particular to each sextant, and can be either plus or minus.

2. Dip

This is found by reference to the Nautical Almanac. Dip is always subtracted.Dip is the angle between the horizontal plane through the observer's eye and the visible horizon (see Fig 2.1). It occurs because the eye is always above the sea level so that the observed altitude is always greater than the altitude as measured from a point at sea level, where theoretically the horizon would be in a true horizontal plane.

Fig 2.1 Dip is determined by height of eyeThe amount of correction depends on the height of eye (HE) of the observer above sea level. The correction for a tabulated HE is diagonally to the right of the HE. For example, the correction for a HE of 2.8m would be 2'.9. This would also apply to a HE of 2.7m.

Fig 2.2 Nautical Almanac extract: Altitude correction table showing dip3. Semi-diameter/Refraction/Parallax

These are combined as a single correction which is found in the Nautical Almanac.

Semi-Diameter

The true altitude is the angle between the true horizon and the centre of the observed heavenly body (HB). Stars have no visible diameter but both the sun and moon have appreciable diameters. Sextant readings should be made by measuring the upper or lower edge (limb) on the horizon and making a correction for half the body's diameter, not by guessing where the centre of the HB is on the horizon.

Refraction

Light passing from outer space into the earth's atmosphere is refracted. Refraction is at a maximum when the HB viewed is low down near the horizon, diminishing the zero when the HB is directly overhead.

Fig 2.4 Refraction the heavenly body's Altitude appears to be higher than it

actually is ParallaxThe altitude of a HB as measured from the surface of the earth differs from that which would be found if it were measured from the centre of the earth, which is the condition required for true altitude. The difference is called parallax. Parallax is greatest when the altitude is low and diminishes to zero when the HB is directly overhead.

Fig 2.5 Parallax if greater when altitude is lowParallax also varies as the distance between the HB and the earth changes. The moon's parallax can be up to 61' in arc as it is relatively near the earth. The sun's parallax is fraction, never exceeding 0'.15 and parallax of all other HBs is negligible.

Total correction

Semi-diameter, refraction and parallax are combined in a single total correction found in the Nautical Almanac for the observed HB's particular altitude. For example, if for a month in May the apparent altitude was 46 10'.01 then the correction to apply would be 16'.7. This correction would apply to all apparent altitudes between 45 31'.0 and 48 55'.0.

Fig 2.6 Nautical Almanac extract: Altitude

correction table sun's total correctionNote that the moon's parallax changes so markedly that it is given as a separate correction.Example 2a: Corrections to sextant altitude

An observation of the sun's lower limb taken in November gave a sextant reading of 34 25'.0. Height of eye 2.5m. Index error 2'.0. Refer to figures 2.2 and 2.6

Sextant Altitude (SA) 3425'.0

Index Error (IE) - 2'.0

Dip (HE 2.5m) - 2'.8

Apparent Altitude (AA) 34 20.2

Correction (Lower Limb/LL Nov) + 14'.9

True Altitude 34 35'.1IV

I

II

III