Astron user notes ( 14)

Find transit

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 15^th. (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 15^th. (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 15^th. (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

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

2024 Oct 15^th. (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.

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

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

2012 May 25 N50 00.0 E000 00.0. Mars.

Find transit

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

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

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