How to calculate Lunitidal Interval UTC differential & Longitude value for a tide watch. Ballycastle
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- เผยแพร่เมื่อ 11 ธ.ค. 2011
- This is a short video on how to calculate the Lunitidal Interval and other relevant information for your tide watch
* UTC Differential
worldtimeserver.com
*Longitude Value
earthtools.org
Information needed to calculate the Lunitidal Interval:
*Moonrise time (a)
*Moonset time (b)
*Time of high tides for this day and the next day
1. b - a = c
2. c / 2 = d
3. a + d = e
4. f - e = x
1. For Ballycastle, Antrim, Ireland
12/12/2011
Moonrise at 18:00(a)
Moonset at 09:58(b)
b - a = c
09:58 - 18:00 = 15:58(c)
2. c / 2 = d
15 / 2 = 7.5 ---- 07:30
58 / 2 = 29
07:30 + 29 = 07:59 (d)
3. a + d = e
18:00 + 07:59 = 01:59 (e)
4. Next high after 01:59 is on the 13/12/2011
@ 08:26 (f)
f - e = x
08:26 - 01:59 = 06:27 (x)
So the Lunitidal Interval is 6 hours 27 minutes
So lets recap on what we have done and double check it.
1. We worked out how long the moon will be in the sky.
15:58
2.we divided this time in half to work out how long it would take from moonrise for the moon to be directly above our longitude (moon up)
07:59
3.we added the time it took to be above our longitude to moon rise to give us the exact time it would be moon up.
01:59
4. We found the next high tide after moon up and worked out the time difference between moon up and the high tide giving us our Lunitidal Interval.
06:27
What other information do we need to set my tide watch?
* UTC Differential
worldtimeserver.com
*Longitude Value
earthtools.org
55.2055°N 6.246°W
Longitude Value 6.W - บันเทิง
Thanks. Using your calculations I have converted this to a spreadsheet (in Excel 2010) which requires you to simply add moonrise, moonset and next high tide, then does all the calculations for you.
nicely explained - thanks.
Many thanks, nicely explained
Thanks Pretendanought - very useful indeed.
@budoonk I'm glad I was able to help, All the best
@OctagonElmo Hi yes there will be a difference on a day to day running of the lunitidal cycle but If you set your lunitidal interval on a full moon or new moon it should be at its most accurate. Unfortunately only setting the interval once can loss and gain minutes over its cycle from when you set it but will always fall back into its pattern in the next cycle and so on. As I said it is just finding the happy medium and this will be achieved on the full or new moon. I hope this helps.
Moonset (09:58) in this example is actually next calendar day right? (not 12th but 13th). I guess most of misunderstanding comes from there.
@budoonk Lunitidal interval for Digby, Annapolis Basin, NS 10:48. UTC Differential 4. Longitude Value 65.W
I researched a little and figured out this formula myself, but I got a different number for every day. I thought I was doing it wrong, so I searched some more and came upon your video. Turns out that the formula I figured out was correct after all. But why do the results change every day by 5-10 minutes? I can't be calculating and resetting my watch every day!
@pretendanought Thanks! I will set it again at the next new moon. (Or I could probably do it now, using the data from the previous full or new moon.) Good advice.
How do you get 9:58-18:00 = 15:58??? Having a hard time following this.
09:58-06:00pm(18:00)=3:58pm(15:58).
@@chemohdsaufi327 So you are getting confused here, remember that the 18:00 (pm) is from the the previous evening, the 9:58 is the next morning hence the time difference
@@pretendanought everything would be much easier if you put dates next to all the times, so we could understood which time was which date...
@budoonk Sorry the I just noticed that I put 4 for the UTC Differential it should be -4
i used a website to calculate the lunitidal interval to set on my g shock watch and i put it in but it has the tides incorrect when i check them on the tide calendar. is this website accurate or did i mess up somewhere else? www.lunitidal-interval.com
when i calculated it myself using this formula a few weeks ago it was also incorrect im so confused
What is 8:26?
same question? I think that's when the tide starts to rise.
None of this makes sense. Someone just tell me what it is for perth. 115º Longitude
"How do you get 9:58-18:00 = 15:58??? Having a hard time following this."
EXACTLY! Surely the difference between 09.58 & 18.00 is 8 hours 2 minutes?
OK so I see where your having problems here, you have to remember that we are taking away and not adding so we are trying to find the time difference between 9:58 in the morning and 18:00 from the evening before. if we add 12 hours to 18:00 (6:00 pm) we will be at 06:00 (6:00am) the next morning add 3:58 to this and what time will it be? 09:58 (9:58am) so 12 hours + 3:58 =15:58 time can be confusing to calculate especially between two different dates. it can be hard to get your head around.
or you can go like 1800 to 2400 is 6 hours and plus 0958 is 1558.
@@pretendanought to me this just confuses me more.. why are we adding 12 hours anyd where did you get 3:58 from?? This whole thing is just frustrating
@@jaredsaint2362 I can understand why this can be confusing especially if you are not fluent with mathematical formulas. Believe me it took me along time to come up with it. I made this years ago and if I get time I will make a more clear video on this. The only advice that I can give you is to assign your information to my letters and follow my formula. Remember tht you are dealing with time here so consider this when you are dividing. Newer watches are easier to set now I have a Casio Gulfmaster and you don't need this equation. If you are really stuck on me the location that you want it for and I will calculate it for you.
@@pretendanought okay so I'm in winnipeg my moon rise is 1:56pm (1356) and my moon set 10:38pm (2238).. perhaps you could show me the formula with my data??
That's the download link below - anal youtube won't let me post urls...
@budoonk Sorry the I just noticed that I put 4 for the UTC Differential it should be -4