The first tropical storm of the season has started in the southern hemisphere. Following the relinquished northern sphere of influence there was an hiatus of about 10 days without a tropical storm, longer if you don’t count the way that they petered out. There is no physics that explains the details of the phenomenon that affects the planet so completely twice each year. For my money it is all to do with the extent of the ice around Antarctica. The amount that occurs varies (with the seasons, obviously) but the amount that builds and melts in the seasons is controlled by a cycle of the moon that varies how far north and south the declination can go every month.
The declination of the moon varies a little each month covering as much as 10 degrees in as many years. You should know that the declination of the sun changes a little every day for six months during which time it runs from the southern reaches (The Tropic of Capricorn) to the northern most point (the Tropic of Cancer) and back again 6 months later. It crosses the equator twice in this time at spring and autumnal Equinoxes.
The sun moves exactly 23.5 degrees every 6 months but the moon moves in a much more complicated schedule, reaching about 5 degrees north of the tropics every 11 years. OTOH of course because of that 5 degree aberration the moon also fails to reach the tropics every 11 years. I believe this is called the nodes or nodal cycle.
I am pretty sure it isn’t the Saros, whatever.
The best way for you to understand lunar declinations rather than look up the various cycles is to run a few random dates through this website:
http://www.fourmilab.ch/cgi-bin/Solar/action?sys=-Sf
It brings up a table like this one:
Ephemeris:
Right Distance From 47°N 7°E:
Ascension Declination (AU) Altitude Azimuth
Sun 15h 28m 30s -18° 53.3′ 0.989 -61.140 164.230 Set
Mercury 14h 41m 7s -14° 16.6′ 1.311 -57.117 -173.071 Set
Venus 15h 52m 16s -19° 58.2′ 1.703 -60.688 152.511 Set
Moon 11h 17m 44s +1° 46.6′ 63.3 ER -21.779 -118.517 Set
Mars 19h 10m 44s -23° 54.3′ 1.762 -35.048 91.517 Set
Jupiter 9h 37m 49s +14° 51.6′ 5.168 3.997 -107.580 Up
Saturn 15h 35m 37s -17° 20.0′ 10.934 -59.262 161.565 Set
Uranus 0h 49m 10s +4° 31.6′ 19.258 39.430 42.946 Up
Neptune 22h 27m 41s -10° 26.5′ 29.777 7.296 66.095 Up
Pluto 18h 49m 20s -20° 41.1′ 33.428 -36.497 98.576 Set
|Look at the row for the moon:
Moon 11h 17m 44s +1° 46.6′ 63.3 ER -21.779 -118.517 Set
The important columns will have a plus or minus sign on it:
+1° 46.6′
And that will vary by about 4 or 5 degrees every day until it reaches maximum north or south. Zero is the equator, plus is north and minus is south.
It may seem the long-way of doing it but it really is the only way to understand it all properly. The truth is that astronomy is full of Greek and maths and meaninglessnesses that are never going to make much sense to anyone.
And the worst thing about the bullshit is that it doesn’t have to be like that. Any fool can navigate. If only he or she doesn’t let the classically trained mumbo jumbo artistes spoil it for them.
Most of the web pages dedicated to explaining this stuff go on about perigee aqnd Apogee as well as phases and other cycles. All are irrelevant as far as the bald facts of declination are concerned. Yet some sites do com,e close:
http://www.astropixels.com/ephemeris/moon/lunarstandstill2001year.html for example after going off course with the same old sameold he write:
Greatest Annual Lunar Standstills: 2001 to 2100 Greenwich Mean Time (GMT)
Year Minimum Dec Maximum Declination (angle to the equator)
2001 Dec 16 07:51 -24.250 Dec 3 06:54 24.246
2002 Dec 6 07:00 -25.808 Nov 23 12:14 25.812
2003 Nov 26 09:16 -27.092 Nov 13 10:16 27.105
2004 Oct 19 08:00 -28.048 Nov 2 01:32 28.042
2005 Oct 9 16:42 -28.604 Sep 25 06:42 28.594
2006 Mar 22 16:53 -28.725 Sep 15 01:28 28.725
2007 Mar 12 16:11 -28.608 Feb 25 23:35 28.600
2008 Mar 1 08:03 -28.030 Feb 16 06:10 28.043
2009 Jan 22 14:02 -27.081 Feb 5 14:55 27.083
2010 Jan 12 08:33 -25.796 Jan 26 21:04 25.783
2011 Jan 2 10:06 -24.242 Jan 16 22:51 24.221
2012 Jan 20 02:12 -22.492 Jan 6 21:46 22.539
2013 Jan 9 15:22 -20.879 Jan 23 05:12 20.816
2014 Jan 27 16:31 -19.396 Jan 13 08:14 19.501
2015 Jan 18 06:17 -18.577 Jan 3 17:53 18.650
2016 Dec 29 03:30 -18.958 Dec 14 21:43 18.937
2017 Dec 19 09:31 -20.062 Dec 5 11:43 20.015
2018 Dec 9 11:12 -21.539 Dec 23 11:48 21.550
2019 Dec 26 20:11 -23.227 Dec 13 20:57 23.226
2020 Dec 15 22:23 -24.879 Dec 3 01:22 24.882
2021 Dec 6 02:25 -26.331 Nov 22 22:43 26.342
2022 Oct 30 01:04 -27.500 Nov 12 14:17 27.497
2023 Oct 20 09:19 -28.305 Oct 5 20:31 28.294
2024 Oct 9 11:53 -28.684 Sep 24 17:04 28.695
2025 Mar 22 06:47 -28.719 Mar 7 15:56 28.710 s portion of his page to establish the simple facts. Now look up the dates for the southern ocean oscillations and you will see why the Australian Bureau of Meteorology publish such fascinating charts. (That is BoM charts are fascinating. They publish them because they are paid to do so. I don’t think they are allowed to go into any detail about them. Either that or the wealth of such detail has passed them by.)
A fuller list can be found here:
http://www.astropixels.com/ephemeris/moon/lunarstandstill2001.html
And yes I appreciate that lists of the El Nono La Nina southern oscillation have yet to be made for this millennium. But at least they have made a start.
I wrote to Fred Espenak at the NASA site where I get my phase data asking him to make lunar declination tables. Apparently he had retired by then. They sent me the link to the astronomical data he had composed while there. I found his present site by accident:
http://www.astropixels.com/index.html
Nice one, Mr Espenak; nice one!
I wrote to Fred Espenak at the NASA site where I get my phase data asking him to make lunar declination tables. Apparently he had retired by then. They sent me the link to the astronomical data he had composed while there. I found his present site by accident:
http://www.astropixels.com/index.html
Nice one, Mr Espenak; nice one!
Please define Declination.
Viewed face on, the equator runs across the middle of the planet anything below that is Declination South anything above it is northern declination.
The moon runs north to south in 14 days then back up in the following 14. The sun does the same in six months and back in another 6.
On the Formilab page the colours green and blue perform the same notification.
I apologise for not replying sooner but I never though anyone would read my stuff.
I learned to use the Astrono,ical rables for Navigators. (not very well.) The declination differs from the pot of view of Asronomical tables I don’t understand them.
Using a Nautical Amanack (https://www.fourmilab.ch/cgi-bin/Solar/action?sys=-Sf for example)
I get these tables one bloody page at a time(I gather Celestica does better but I don’t know how to use it):
Right Distance From 47°N 7°E:
Ascension Declination (AU) Altitude Azimuth
Sun 11h 9m 45s +5° 23.1′ 1.007 -27.902 -136.350 Set
Mercury 10h 31m 35s +11° 5.3′ 1.246 -18.240 -130.566 Set
Venus 13h 44m 37s -15° 20.6′ 0.511 -58.334 178.288 Set
Moon 10h 39m 29s +11° 25.6′ 57.5 ER -18.958 -132.494 Set
Mars 20h 12m 5s -25° 17.8′ 0.482 -13.229 66.950 Set
Jupiter 15h 4m 27s -16° 29.5′ 5.780 -54.942 143.468 Set
Saturn 18h 11m 2s -22° 42.8′ 9.737 -31.518 89.625 Set
Uranus 2h 0m 38s +11° 41.6′ 19.159 54.449 -8.334 Up
Neptune 23h 6m 28s -6° 48.8′ 28.933 26.257 43.699 Up
Pluto 19h 20m 33s -22° 4.2′ 33.090 -19.319 78.003 Set
I am not really interested in much of it except for the Lunar positions.
Moon 10h 39m 29s +11° 25.6′ 57.5 ER -18.958 -132.494 Set
Right Ascension is the position against the backdrop of the stars.
The datum is generally the first point of Aires. or Vernal equinox I am not sure.
Declination +11° 25.6′
This is the angle made by the Moon (in this case) relative to the equator. That is: 11 degrees or so north of it, which is about 40 degrees below my house.
57.5 ER. All the other orbits are given in Astronical distances which are fraction of or multiples of 1 where 1 is the distance of earth from the sun.
The moon is different, hence the codicil ER
The author of the application lives in Switzerland and for some reason I don’t understand seems to think people want to know what his positions are at all times:
-18.958 -132.494. From 47°N 7°E. But what else can you expect for free from the bloody Swiss?
Set means Setting, that is the declination is dropping. Some years the moon reaches higher than the equator every month.
Some years it reaches less but it rises and sets over a period of some 27.3 days IIRC. When it gets to the equinoctial positions it can be moving 5 or 6 degrees in a day. When it get to its TdC or BdC it can seem to hang there for a couple of days.
HTH. Oce again sorry for the delay.