Monday, 21 December 2020

Solstice sunrise times and sun position across Ireland and the World. Interesting Astronomically and Spiritually ;-)

Newgrange solstice, webcam at Newgrange caught a lovely pre-solstice sunrise on morning of Dec 20th 2020. Weather dependent and morning of Dec 21st was overcast and rainy. Video links here:

 https://www.gov.ie/en/news/eea6b-winter-solstice-at-newgrange-2020/?referrer=james

 https://youtu.be/8anbIH-XfPU?t=954  Dec 20th 2020 Newgrange solstice start 15mins into video

 https://youtu.be/8anbIH-XfPU?t=1323 Sun rises at 22 mins in

 https://youtu.be/8anbIH-XfPU?t=1551 25:55 ambient light on floor

 https://youtu.be/8anbIH-XfPU?t=1568 26:08 first ray of light on floor . . . 

Solstice sunrise times and sun position across Ireland.

Winter Solstice sunrise in Malin Head North Ireland today at 8:55am with sun at 133° (2° N of SE). Sunset at 16:00pm with sun at 227° (2° N of SW) 7hrs 5mins of daylight today, that is 31 mins less than Cape Clear in the South-West. timeanddate.com/sun/@2962718

Winter Solstice sunrise in Dublin today at 8:38am with sun at 130° (5° N of SE). Sunset at 16:08pm with sun at 230° (5° N of SW) 7hrs 30mins of daylight today here. 1 minute more of daylight tomorrow. timeanddate.com/sun/@3315278

Winter Solstice sunrise in Cape Clear SW Ireland today at 8:41am with sun at 128° (7° N of SE). Sunset at 16:31pm with sun at 232° (7° N of SW) 7hrs 51mins of daylight today, that is 20 mins more than Dublin. timeanddate.com/sun/@2965457

Ireland is roughly 440km high and 300km wide:

Malin Head to Cape Clear vertical (North-South) distance = 430km ish 

  == 4° of latitude  55° 30' N to 51° 30' N

Dublin to Cape Clear horizontal (East-West) distance = 300km ish

  == 4° of longitude  6°W to 10°W  

  4° of longitude is 4/360 of circumference of earth = 1/90th, 1/90th of 24 hours is 16 minutes. (yes, if you traverse Ireland 90 times you will have covered 27000km the same distance it takes to circumnavigate the globe . . . at 53° of latitude. Which is a bit shorter than circumnavigating at the equator (about 111.3*360 = 334*120 = 668*60 = 40080km).   https://en.wikipedia.org/wiki/Longitude#/media/File:WGS84_angle_to_distance_conversion.svg     https://en.wikipedia.org/wiki/Earth

Cape Clear will have later sunset/sunrise than places further East but has earlier sunrise and more daylight as it is furthest South in Ireland. 

Handy that Ireland is both 4° of longitude wide as well as 4° of latitude high. Roughly now, a few bits of Ireland stick out a bit. Latitude - longitude grid boxes are squares at equator, lines of longitude meet at the poles so the width of latitude - longitude grid boxes narrows as you go further North. 

There are 180 latitudes and they are about 110km high. There are 360 longitudes and they are 111.3km wide at Equator, about 75km wide at Ireland's latitude (around about 53°N), and narrowing to no width at the North pole. https://en.wikipedia.org/wiki/Longitude

Good info and nice sunset/sunrise day/night length graphs at timeanddate.com.

The Sun rises in the East and sets in the West, . . . generally speaking. 

The Sun rises closest to the East (and sets in the West) at the Spring and Autumn equinoxes, it will be closest to East (and West) along the Equator at the equinoxes. On the Winter solstice the sun is most directly above the tropic of Cancer so the sun rises closest to the East (and sets closest to the West) along this tropic at this time. On the Summer solstice the sun is most directly above the tropic of Capricorn so the sun rises closest to the East (and sets closest to the West) along this tropic at this time.  

For locations on the Earth in the Northern hemisphere and above the tropics the sun rises and sets further South during the winter getting to about SE and SW (at Ireland's Latitude) on winter solstice, thus giving shorter days. The sun rises and sets further North during summer getting to about NE and NW (at Ireland's Latitude), thus giving longer days.

It's the other way around in the Southern hemisphere (below the tropics).

Between the tropics the length of day and night is close to equal the whole year. The sun also rises and sets at nearly right angle to the planet so there is less twilight time. 

At the equator at 0° latitude, e.g. in Libreville, Gabon in Africa (a smidge North of the Equator at 0°30'N 9°30'E) daylight hours range over 2mins very consistent. Sun ranges from 23° North and South of due East at the solstices.     https://www.timeanddate.com/astronomy/gabon/libreville

Winter solstice Sunrise at 06:17 113° ESE, Sunset at 18:23 247° WSW, Daylight 12hrs, 6mins, 10s

Spring Equinox Sunrise at 06:26 90° East, Sunset at 18:32 271° West, Daylight 12hrs, 6mins, 30s

Summer solstice Sunrise at 06:19 67° ENE, Sunset at 18:28 293° WNW, Daylight 12hrs, 8mins, 40s

Autumn equinox Sunrise at 06:11 90° East, Sunset at 18:18 270° West, Daylight 12hrs, 6mins, 27s

At the tropic of Cancer at 23°26'22" North of the Equator, e.g. in Muscat, Oman on the Arabian peninsula in the Middle East (a smidge North of this tropic at 23°35'N 58°23'E) daylight hours range over 3hrs from shortest day with 10hrs 41mins of sun to longest with 13hrs 35mins. Sun ranges from 26° North and South of due East at the solstices.     https://www.timeanddate.com/sun/oman/muscat

Winter solstice Sunrise at 06:43 115° ESE, Sunset at 17:24 245° WSW, Daylight 10hrs, 41mins

Spring Equinox Sunrise at 06:08 89° East, Sunset at 18:17 271° West, Daylight 12hrs, 8mins, 24s

Summer solstice Sunrise at 05:19 64° ENE, Sunset at 18:55 296° WNW, Daylight 13hrs, 35mins, 30s

Autumn equinox Sunrise at 05:54 89° East, Sunset at 18:03 271° West, Daylight 12hrs, 9mins

At 53°N e.g. in Ireland daylight hours range over 9hrs 30mins from shortest day with 7hrs 30mins of sun to longest with 17hrs. Sun ranges from 45° North and South of due East at the solstices.     https://www.timeanddate.com/sun/ireland/dublin

Winter solstice Sunrise at 08:38 130° SE, Sunset at 16:08 230° SW, Daylight 7hrs, 30mins

Spring Equinox Sunrise at 06:24 88° East, Sunset at 18:40 272° West, Daylight 12hrs, 15mins

Summer solstice Sunrise at 04:56 47° NE, Sunset at 21:57 313° NW, Daylight 17hrs

Autumn equinox Sunrise at 07:11 89° East, Sunset at 19:23 271° West, Daylight 12hrs, 12mins

At -90°S at the South Pole in Antartica  daylight hours range over 24hrs from shortest days with 0hrs  of sun for ?? days during the ?summer?winter? to longest with 24hrs for ?? days during the ?winter?summer?. Sun ranges over the full 360°. Rising in the North at end of "summer" traversing through East to South and West then setting in North. Rising in East and settign in West at equinox. Rising and setting in the South in the very short days just before the start of "winter".   https://www.timeanddate.com/sun/antarctica/south-pole

Winter solstice Sun up all day at highest altitude of the year at 23.5° all day, Daylight 24hrs

  Height of Antarctic Summer

Spring equinox - the one Sunset of the year!!, sun skirts horizon at altitude of 0° all day, Daylight/twilight all day

  Start of Antarctic Winter, Sun down all day every day from now until the next Equinox. Yeow.

Summer solstice Sun down all day at lowest altitude of the year -23.5° all day, Daylight 0hrs

  Depth of Antarctic Winter 

Autumn equinox - the one Sunrise of the year!!, sun skirts horizon at altitude of 0° all day, Daylight/twilight all day

  Start of Antarctic Summer, Sun up all day every day from now until the next Equinox. Yeow.


Interesting.

Madness.

Pretty Diagrams thanks to wikipedia:

https://en.wikipedia.org/wiki/Equinox#/media/File:North_season.jpg

Earth's seasons through far right Winter/December solstice, Spring/March equinox, Summer/June solstice, Autumn/September equinox
The Earth's seasons through the year. Far right Winter/December solstice, Spring/March equinox, Summer/June solstice, Autumn/September equinox.

Stop.

And consider this diagram a bit more.

I had seen this diagram a good bit but not taken it in properly.

Consider . . . the earth and day and night length as it rotates each day in these positions.
Consider how high the sun gets in the sky.

At the poles, a full half year with 24hrs daylight then 24hrs night, sun steady at same altitude above/below horizon each day (at 23 degrees above horizon at height of summer solstice, down to 0 degrees skirting horizon at equinoxes, down to 23 degrees below horizon at depth of winter solstice).
Inside the polar circles 23 degrees from poles, night and day lengths very from nearly 24hrs/0hrs in mid-winter/summer to quickly changing night and days lengths near equinoxes where there is a 12hr/12hr day. 
At the mid-latitudes from 23 degrees polar circles to the tropics 23 degrees from equator; Night/day lengths short down to 3/4/5/../10 hours and up to 14/../19/20/21 hours.
In the tropics less variation through the year day or night length from 10 to 14 hours.
At the equator very little variation day and night lengths close to 12 hours all the time.   

 and https://en.wikipedia.org/wiki/Equinox#/media/File:Hours_of_daylight_vs_latitude_vs_day_of_year_with_tropical_and_polar_circles.svg

 from https://en.wikipedia.org/wiki/Equinox

At the poles 0 hours OR 24 hours of night and day. Polar circles to 23 degrees with shorter day/night briefly up to 12hr at the equinoxes. Middle latitudes with from 3,4,5 hours minimum to 19,20,21 hours max length. Tropics with from 10 to 12 hours day or night lengths.
Hours of Daylight on different days of year by latitudes (Dublin, approx. middle latitude of Ireland is at latitude 53 degrees North, daylight from max 17hrs at Summer solstice to min 7hrs 30min at Winter solstice)

 


https://skyandtelescope.org/astronomy-resources/sunrise-moonrise-east/  


We can see the Sun rises due east at 90° on the 18th and 19th a couple of days before the equinox. Spring equinox sun-rise times and positions for March 2021 (from timeanddate.com) for Dublin, Ireland:

16Sunrise

06:41  (92°)
Sunset

18:35  (269°)
Day length
(hours, . .


11:53:48

. . diff mins)

+4:34
Astro Twi-
start

04:37
-light
end
20:40
Naut Twi-
start

05:22
-light
end
19:55
Civil Twi-
start

06:05
-light
end
19:12
NOON time and altitude:

12:38 (33.1°)
148.827
1706:39  (91°)18:37  (269°)11:58:23+4:3404:3420:4205:1919:5706:0219:1412:37 (33.5°)148.868
1806:36  (90°)18:39  (270°)12:02:58+4:3404:3120:4505:1719:5906:0019:1612:37 (33.9°)148.909
1906:33  (90°)18:41  (271°)12:07:33+4:3404:2820:4705:1420:0105:5719:1812:37 (34.3°)148.949
Rise
06:33
rising at 90° == East
Meridian
12:37
180° == South sun at 34° altitude
Set
18:41
setting at 271° == West
12:37

Altitude

34°

Heading

180°S

Position

Day
2006:31  (89°)18:43  (271°)12:12:08+4:3404:2520:4905:1120:0305:5419:2012:36 (34.7°)148.990
2106:28  (88°)18:45  (272°)12:16:42+4:3404:2220:5205:0820:0505:5219:2212:36 (35.1°)149.031
2206:26  (87°)18:47  (273°)12:21:17+4:3404:1920:5405:0620:0805:4919:2412:36 (35.5°)149.073



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