Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

Bart Senior wrote:
Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

I guess it depends on the location. For my area, it's a couple of hours or
so after lunar noon, so about midnight to 1am for the above example.


--
Wally
www.forthsailing.com
www.wally.myby.co.uk

Ok, I'll give it a try -

Halfway between moonrise and moonset is 10 pm local time, which is the time of
transit of the local meridian. To this we must add the "Local Establishment" or
the "Lunitidal Interval" (actually the proper terms are "high water full and
change" or "mean high water lunitidal interval") to get the time of the next
high tide.

This was published on old charts. My 1867 Boston Harbor chart lists the
"Corrected Establishment" (average of all high water intervals) for Boston Light
as "XIh XIIm". This mean you add 11 hours and 12 minutes to the time of local
meridian passage of the moon to get the time of the next high tide.

Tides watches usually require setting the Lunitidal Interval for a particular
spot. Of course, this only works for semidiurnal tides.


"Bart Senior" wrote in message
. net...
Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

What location has moon rise and set 12 hours apart? If moon rise is at
4pm the next high tide here will be about 5:30pm -I think.

Cheers

Bart Senior wrote:

Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

Navigator wrote:
What location has moon rise and set 12 hours apart?

Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about 12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.


--
Wally
www.forthsailing.com
www.wally.myby.co.uk

Wally wrote:
Navigator wrote:

What location has moon rise and set 12 hours apart?


Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about 12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.


The devil _is_ in the detail and is it ever 12 hours????

Cheers

Navigator wrote:

The devil _is_ in the detail and is it ever 12 hours????

What part of 'find lunar noon' are you ignoring in lieu of trolling for
nanosecond-precise astronomical timing?


--
Wally
www.forthsailing.com
www.wally.myby.co.uk

"Navigator" wrote in message
...


Wally wrote:
Navigator wrote:

What location has moon rise and set 12 hours apart?


Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about 12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.


The devil _is_ in the detail and is it ever 12 hours????


Why not? What's the problem? Or are you making the sophomoric argument that
its very unlikely to be "precisely" 12 hours? It certainly isn't hard to find
places and times where its within a couple of minutes. Certain latitudes are
more favorable than others for this situation to exist, but there's nothing the
precludes it.

Have a go with:
http://aa.usno.navy.mil/ select "Data Services" and then "Table of
sunrise/sunset ..."

1 pt to you Wally.

High Tide will be somewhat close to the
mid point between moonrise and moonset.

I have not researched many lcoations but I'd
estimate +/- an hour for more locations.

In my location High tide occurs about an hour
before that mid point.

Geographical factors will have a big influence.
A body of water might be north-south like the
Bay of Fundy or Gulf or California versus
east-west like Long Island Sound.

I find it handy to be able to judge high tide
by looking at the moon. I can add or subtract
to estimate when the next high or low tide will
be.

As you can see we have at times nearly a 9
foot swing, so tidal currents coupled with river
current can cause problems with launching if you
are like me, and using a chain hoist. At times
I cannot drop the boat all the way into the river.
I need longer lift straps.

Here is an example for my location:

2004-05-02 5:26 PM EDT Moonrise
2004-05-02 7:51 PM EDT Sunset

2004-05-02 10:09 PM EDT 7.80 feet High Tide

2004-05-03 4:33 AM EDT -0.49 feet Low Tide
2004-05-03 5:06 AM EDT Moonset
2004-05-03 5:47 AM EDT Sunrise

2004-05-03 10:38 AM EDT 7.16 feet High Tide

2004-05-03 4:45 PM EDT -0.14 feet Low Tide
2004-05-03 6:42 PM EDT Moonrise
2004-05-03 7:52 PM EDT Sunset

2004-05-03 10:55 PM EDT 8.06 feet High Tide

2004-05-04 5:21 AM EDT -0.84 feet Low Tide
2004-05-04 5:33 AM EDT Moonset
2004-05-04 5:46 AM EDT Sunrise

2004-05-04 11:27 AM EDT 7.20 feet High Tide

2004-05-04 4:35 PM EDT Full Moon
2004-05-04 5:31 PM EDT -0.26 feet Low Tide
2004-05-04 7:53 PM EDT Sunset
2004-05-04 8:01 PM EDT Moonrise

2004-05-04 11:42 PM EDT 8.21 feet High Tide

2004-05-05 5:44 AM EDT Sunrise
2004-05-05 6:06 AM EDT Moonset

You will note that the time of high tide slips
about 50 minutes every day and the interval
between high tides is about 12.5 hours.

A good sailor will know what these factors are
for his or her location to figure the next
high tide.

Bart Senior

"Wally" wrote

Bart Senior wrote:
Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

I guess it depends on the location. For my area, it's a couple of hours or
so after lunar noon, so about midnight to 1am for the above example.

2 pts. Great answer Jeff. an extra point for adding
worthwhile content.

Can you name two places where tides are diurnal?

What are spring and neap tides and how can you tell by
observing the moon, if a tide will be spring or neap?

Jeff Morris wrote

Halfway between moonrise and moonset is 10 pm local time, which is the
time of
transit of the local meridian. To this we must add the "Local
Establishment" or
the "Lunitidal Interval" (actually the proper terms are "high water full
and
change" or "mean high water lunitidal interval") to get the time of the
next
high tide.

This was published on old charts. My 1867 Boston Harbor chart lists the
"Corrected Establishment" (average of all high water intervals) for Boston
Light
as "XIh XIIm". This mean you add 11 hours and 12 minutes to the time of
local
meridian passage of the moon to get the time of the next high tide.

Tides watches usually require setting the Lunitidal Interval for a
particular
spot. Of course, this only works for semidiurnal tides.