Astron user notes ( 14)



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Find transit



UT

Zn

Transit 22:25:19

22:25:19

179.9997071

22:25:20

180.0049603

Theoretical Correction -5m 55s

(5m 55s is also value computed by MICA, Multiyear Interactive Computer Almanac by USNO. Above transit and culmination times also agree with MICA to within 0.4 secs.)

Enter Astron. 2024 Oct 15. 22:31:14 Moon N50 00.0 W000 00.0. Hs 39 06.4 IC=-3.8, HoE = 24ft. Lower limb.

Astron initial position. N50 00.9 W001 25.7

Astron Dec at 23:31:14 is N00 20.0 and at 22:31:14 is N00 01.8, so Dec Rate is +18.2.

Enter Astron correction table with Dec Rate + 18.2 and SOG 0 knots.

Astron formula correction -5m 55s.

Astron Corrected Time 22:25:19

Astron Corrected Lat N50 00.0

Astron Corrected Long E000 00.0

23.8.3 Moon example. Setup as 23.8.2. Moving observer at 180°/10kts. (No E/W component)

Worksheet for vessel at 50N 0W at ACTUAL transit time of 22:25:19. (IC=-3.8, HoE = 24ft. Lower limb.)

2024 Oct 15th. (Moon Dec Rate +18.2’/hour)
Find culmination. (Transit as 23.8.2:- 22:25:19)

UT

Lat

Long

Hc

Hs

Uncorrected

Lat


Uncorrected

Long


Zn

22:25:19

50.0

0.0

40.00089801










179.9997071

























22:34:28

49 58.475

0.0

40.03677884













22:34:29

49 58.472222

0.0

40.03677885

(40 02.2)



39 07.7

50.0098844

(50 00.6)



-2.213047919

(W002 12.8)






22:34:30

49 58.469444

0.0

40.03677862













Theoretical Correction -9m 9.5s

Enter Astron. 2024 Oct 15. 22:34:29 Moon N50 00.0 W000 00.0. Hs 39 07.7 IC=-3.8, HoE = 24ft. Lower limb.

Astron Correction -9m 10s. (9:09)

Astron initial position N50 00.6 W002 12.8

Enter Astron correction table with Dec Rate + 18.2, COG 180 and SOG 10 knots.

Astron formula correction -9m 10s.

Astron Corrected Time 22:25:19

Astron Corrected Lat N50 00.0

Astron Corrected Long E000 00.0

23.8.4 Moon example. Setup as 23.8.2. Moving observer at 150°/10kts (Lat and Long components)

Worksheet for vessel at 50N 0W at ACTUAL transit time of 22:25:19. (IC=-3.8, HoE = 24ft. Lower limb.)

2024 Oct 15th. (Moon Dec Rate +18.2’/hour)
Find culmination. (Transit as 23.8.2:- 22:25:19)

UT

Lat

Long

Hc

Hs

Uncorrected

Lat


Uncorrected

Long


22:25:19

50.0

0.0

40.00089801































22:33:52

49 58.7659138

E0 1.108453227

40 01.972824










22:33:53

49 58.76350817

E0 1.110613955

40 01.972835

39 07.4

50.0109781

N50 00.7


-2.068179379

W002 04.1



22:33:54

49 58.76110255

E0 1.112774682

40 01.972833

39 07.5






Culmination 22:33:53.5

Theoretical Correction. -8m 34.5s 22:25:19

Enter Astron. 2024 Oct 15. 22:33:54 Moon N50 00.0 W000 00.0. Hs 39 07.5 IC=-3.8, HoE = 24ft. Lower limb.

Astron initial position N50 00.6 W002 04.3

Enter Astron correction table with Dec Rate + 18.2, COG 150 and SOG 10 knots.

Astron formula correction -8m 34s.

Astron Corrected Time 22:25:20

Astron Corrected Lat N49 59.9

Astron Corrected Long W000 00.1


23.8.5 Moon example. Moving observer different direction. (300°/10kts)

Worksheet for vessel at 50N 0W at ACTUAL transit time of 22:25:19. (IC=-3.8, HoE = 24ft. Lower limb.)

2024 Oct 15th. (Moon Dec Rate +18.2’/hour)
Find culmination. (Transit as 23.8.2:- 22:25:19)

UT

Lat

Long

Hc

Hs

Uncorrected

Lat


Uncorrected

Long


22:25:19

50.0

0.0

40.00089801































22:29:44

50 0.368055556

W0 0.991759818

40 0.540906










22:29:45

50 0.369444445

W0 0.995502308

40 0.540910

39 06.0

50 00.8

W001 04.2

22:29:46

50 0.370833334

W0 0.9992448

40 0.540900









Culmination 22:29:45

Theoretical Correction. -4m 26s

Enter Astron. 2024 Oct 15. 22:33:54 Moon N50 00.0 W000 00.0. Hs 39 06.0 IC=-3.8, HoE = 24ft. Lower limb.

Astron initial position N50 00.8 W001 04.2

Enter Astron correction table with Dec Rate + 18.2, COG 300 and SOG 10 knots.

Astron formula correction -4m 26s.

Astron Corrected Time 22:25:19

Astron Corrected Lat N50 00.0

Astron Corrected Long W000 00.0



23.8.6 Southern Hemisphere check. Moon example. As 23.8.5 except now at S50 00.0.

Worksheet for vessel at 50S 0W at ACTUAL transit time of 22:25:19. (IC=-3.8, HoE = 24ft. Lower limb.)

2024 Oct 15th. (Moon Dec Rate +18.2’/hour)

Interesting to compare with 23.8.5 above. In this Southern Hemisphere, but otherwise similar setup, culmination is now an equal time before transit.


Find culmination. (Southern Hemisphere Transit rechecked as 23.8.2:- 22:25:19)

UT

Lat

Long

Hc

Hs

Uncorrected

Lat


Uncorrected

Long


22:25:19

S50.0

0.0

39.99910198































22:20:53

S50° 00.3696'

E000° 00.9954'

40.0072089










22:20:54

S50° 00.3678'

E000° 00.9918'

40.00721575

39 05.8

S50 00.9

E001 04.0

22:20:55

S50° 00.3666'

E000° 00.9882'

40.00721238









Culmination 22:20:54

Theoretical Correction. +4m 25s

Enter Astron. 2024 Oct 15. 22:20:54 Moon S50 00.0 W000 00.0. Hs 39 05.8 IC=-3.8, HoE = 24ft. Lower limb.

Astron initial position S50 00.9 E001 04.0

Enter Astron correction table with Dec Rate + 18.2, COG 300 and SOG 10 knots.

Astron formula correction +4m 26s.

Astron Corrected Time 22:25:20

Astron Corrected Lat S50 00.0

Astron Corrected Long W000 00.2


23.8.7 Star example.

Dec rate is zero so formula always gives correction of 0 for stationary observer.


23.8.8 Planet example.

2012 May 25 N50 00.0 E000 00.0. Mars.


Find culmination.

UT

Hc.

Hs

Culmination 18:41:43.5

18:41:42

48 06.314497




18:41:43

48 06.314514




18:41:44

48 06.314514!

48 15.6

18:41:45

48 06.314496



Find transit



UT

Zn

Transit 18:41:50

18:41:50

179.9991122

18:41:51

180.0053010

Culmination 18:41:43.5

Theoretical Correction +0m 06.5s

(0m 07s is also value computed by MICA, Multiyear Interactive Computer Almanac by USNO. Above transit and culmination times also agree within 0.5 secs.)

Enter Astron. 2012 May 25 18:41:44 Sun N50 00.0 W000 00.0. Hs 48 15.6 IC=-3.8, HoE = 24ft. Lower limb.

Astron initial position S50 00.0 E001 01.5

Astron Dec at 18:41:44 is N08 06.3 and at 19:41:44 is N08 05.9 so Dec Rate is -0.4. (Actually -0.42)

Enter Astron correction table with Dec Rate -0.4 and SOG 0 knots.

Astron formula correction +0m 6s.

Astron Corrected Time 18:41:50

Astron Corrected Lat S50 00.0

Astron Corrected Long W000 00.1


23.8.9 Planet example with moving vessel.

As above, but COG 120, SOG 0.8kts.

Correction now 0. As expected as Southerly component is 0.4 kts, equalling Southerly Dec Rate.
23.8.10 Testing North/South motion only. (Body Dec Rate zero).

Sun 21 Dec 2017 50N 0 W Velocity 360/10

Transit 11 58 11
Find culmination.

GMT

Lat

Hc

Hs

11:54:02

49 59.30833333

16 34.258858




11:54:03

49 59.31111111

16 34.258860

16 29.8

11:54:04

49 59.31388889

16 34.258851



Find transit



UT

Zn

Transit 11:58:11

11:58:10

179.9954054

11:58:11

179.9993925

11:58:12

180.0033796

Culmination 11:54:03

Theoretical Correction. +4m 08s

Enter Astron. 2017 Dec 21 11:54:03 Sun N50 00.0 W000 00.0. Hs 16 29.8 IC=-3.8, HoE = 24ft. Lower limb.

Astron initial position N49 59.6 E001 02.0

Astron Dec at 11:54:03 and 12:54:03 is S23 26.1 so Dec Rate is 0.

Enter Astron correction table with Dec Rate 0, COG 360 and SOG 10 knots.

Astron formula correction +4m 8s.

Astron Corrected Time 11:58:11

Astron Corrected Lat N50 00.0



Astron Corrected Long W000 00.1

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