# Astron user notes ( 14)

 Page 12/12 Date 07.08.2017 Size 348.43 Kb.

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