Are you ready for the second Bark EUROPA challenge?
Here we go!
One part of the world has the sun in the North at Noon, the other half of the world sees the sun in the South at Noon.
Bark EUROPA will soon see the sun straight above their heads. So, not South and not North, but in their ZENITH. This is the moment when EUROPA will lose her own shadow. There is only one place and one time when the sun will be directly overhead and we challenge you to tell us when!
Klaas will explain to you how to figure out when this moment will be. Follow this blog to be able to read the explanations and ask your questions in the comments! You can also join the eventpage on Facebook, find the link below for the Facebook page.
This weekend on Saturday the 16th and Sunday the 17th you can post your answer in the comments on this blog or on the Facebook and we will announce the winner when Europa meets the sun. Have Fun!
DECLINATION OF THE SUN - Explanation by Captain Klaas
For an easy understanding of the Suns declination you have to think out of the box. Or maybe it’s the other way around, you have to put yourself inside the box.
Imagine yourself sitting in the middle of the earth. Imagine the earth surface is made of glass and you can see the stars, planets, moon and the sun through this glassy surface. Imagine the earth is the middle of the universe like in the past and the Sun and all the stars and planets are turning in 24 hours around you making a complete circle.
You will discover from your central spot inside the earth that the sun will travel on the 21st of March exactly over the Equator (which is of course nicely marked on the glassy surface of the earth.
After this date the sun will make every day a circle around the earth that lies a little bit North of your marked Equator until she reaches another nicely marked line on the earth surface on the 21st of June this circle is called the Tropic of Cancer.
Now imagine that you make a graduation scale from 0° to 90° with 0 on the Equator and 90 on the North pole.
Then you can give the Sun every day a certain number in degrees and minutes depending on the circle she is describing on the Earth’s surface. (Every degree contains 60 minutes also called minutes of arc) The circle that we call the Tropic of Cancer is situated on 23° 26’ North. After the Sun touches this line she will slowly circle down again to the Equator which she reaches at the 21st of September. After that day, she circles down South of the Equator on her way to the Tropic of Capricorn (23° 26’South) which she reaches on the 21st of December.
The books will give you for every date of the year exactly the declination of the Sun.
You can download the Nautical Almanac 2020 for free from the internet (pdf) https://www.nauticalalmanac.it/en/navigation-astronomy/the-nautical-almanac.html
I show you the page for today with in the left upper corner the Sun’s declination for every UTC hour of this day. So now you can calculate the position circle in latitude of the sun for every day and hour.
Next thing is to calculate when the EUROPA is catching up with this slowly North moving Sun.
Only for the interested….. Another little detail is that if you are traveling 90 degrees North from this Tropic of Capricorn you will and up at 66° 33’ North and “surprise” that is exactly the Arctic circle (polar circle) in the Northern Hemisphere.
So we step out of our earth box again and we will discover that this magic number of 23° 26’ is the angle that the axis of our Earth is having constantly while she is turning around her self (in 24 hrs) and while she is traveling around the Sun (in 365 days) The prove is easy to see (if you live in the Northern hemisphere) the axis of our Earth is pointing all around the year to the Polar star. It looks that the whole orbit is turning around this Polar star in 24 hours.
Have fun with your calculations Klaas
EUROPA’s STRUGGLE TO THE NORTH - Captain Klaas gives a calculation clue for the challenge.
The track that the EUROPA is showing the last couple of days is not the shortest route to Scheveningen, EUROPA’s homeport.
The reason for this North-westerly track is the North-east Trade-wind which is ruling this area. The East-West running Finish line for our second challenge is moving every day about 15 Nautical Miles to the North (See my explanation about the Sun declination).
EUROPA is sailing full & by on Starboard-tack which means that she is sailing braced sharp but steering about 5 degrees lower to the wind then possible, this gives her a good speed and drifting less to lee then if she was steering close-hauled.On this course, you are not steering on the compass but on the wind direction and that’s fun for the sailor on the wheel. The skysail (highest square sail) is the indicator, you have to keep the luff-side of this sail just alive. (luffing a little).
EUROPA is making a speed of 6 to 7 knots with a proper blowing Trade-wind.
If you look at EUROPA’s track from the last week you see that she started of with a course (over ground) of 300° and coming slowly around to 330°. It’s obvious that the more Northerly her track becomes the more speed she gains in the Northerly direction.
To make it easier for you I made a little list that gives you, the Course (over ground) and the distance the ship has to sail on that course to gain 1 N.M to the North.
360° 1 Naut. Mile = 1 Naut. Mile
350° 1,02 = 1 N.M.
345° 1,04 = 1 N.M.
340° 1,06 = 1 N.M.
335° 1,10 = 1 N.M.
330° 1,15 = 1 N.M.
325° 1,25 = 1 N.M.
320° 1,33 = 1 N.M.
315° 1,42 = 1 N.M.
310° 1,56 = 1 N.M.
305° 1,75 = 1 N.M.
I hope this will give you another instrument to calculate EUROPA’s “Meeting the Sun, Challenge”
THE NORTH-EAST TRADE WINDS & SOME ANSWERS ON QUESTIONS From Captain Klaas
For a proper calculation of the time that bark EUROPA is passing the declination of the Sun, the N.E. Tradewinds are a major factor.
We can have a check with the course over ground that the Europa is doing at this moment and the forecast from the Windy website
( https://www.windy.com/?18.312,-30.234,6,i:pressure ).
Although we know that captain Eric doesn’t trust the forecast’s close to the Equator very much, it is the only source that is available to us. Strength & Direction of this trade-wind are important and they will change when the Subtropical High pressure system North of the EUROPA is varying in strength and/or position or if a Low pressure system starts interfering with the High. If this happens the whole picture is changing.
The Westerly flowing North Equatorial current is also a small factor but that one is more steady over the whole area that they are crossing at the moment. So the effect of this is already taken in the track that you can see on the website and will be the same for the coming days.
Andreas Mühlmann is bringing up a proper remark. He states that the EUROPA would be very lucky to pass the declination line of the Sun and also have a Noon at the same time. Correct Andreas, that would be a very lucky shot. For our Challenge you just have to take the declination line of the Sun for the hour that the Europa is passing that Latitude and this can be any time of the day or night.Wim Nieuwenhuijse is trying to calculate also the Noon in UTC together with the declination, so for him also the same answer as for Andreas, only the declination is counting don’t bather about the “Greenwich hour angle” or the “Local hour angle” these are for Longitudes that is something we could involve next year So only find out when Europa her latitude and the Sun her declination are the same in degrees and minutes. That day and time in UTC is what we need from you.
Your second question about the “vd” in the Nautical Almanac of 0,7 (hourly change of sun’s declination), that will give you also a speed of 0,7 knots and a daily change of 24x 0,7 = 16,8 N.M per day. Keep in mind that this “vd” is getting less when the sun comes closer to the Tropic of Cancer where she becomes 0 for a while before she is becoming negative and increasing.
Darral Criswell is asking if we are not afraid of Pirates in these areas where EUROPA is sailing at the moment. The EUROPA is following the traditional sailing routes in her voyages around the world. These routes take her most of the time far from the commercial shipping routes. Pirates are in these modern days most of the time operating close to the coast and in areas with lots of commercial traffic. The closest piracy area at this moment is Conakry (Guinea) and the Gulf of Guinea (especially Nigeria) these are all more than 1.000 Miles away from her track.
EUROPA found the Sun this morning. Her 08:00 UTC position is just a little bit North of the Suns Declination of 08:00 UTC. We are waiting for the report from Eric about his exact passage time.
And the winners of the second challenge are.....
On a shared first place with only five minutes away from EUROPA's passage of the sun's declination are:
On a shared second place with only 15 minutes away are:
And the third place and fourth place with 20 minutes and 27 minutes away are:
Bark Europa arrived at a passage of the sun's declination on May 18th at 07:55 UTC
Thanks to everyone who participated! The winners will be hearing from us soon with an invite to have a video chat with Klaas about this challenge and their winning entry!
Hoi Klaas, Bedankt voor deze mooie opgave, 18 mei UTC 06.25' 30". Comment: Stel nu dat ik in California zou wonen dan is post op zondag 17 mei met iets te simpel. See You Wim
Wim Valk | 17-05-2020 21:43 uur
I think 18.5. 7.35 UTC
Kristin | 17-05-2020 20:31 uur
Even in the case that I'm ridiculously wrong: 18.5.2020 19:35 UTC. I hope for some lessons on board in the future ;-)
Matthias Neubauer | 17-05-2020 20:07 uur