Full Moon

I'm not in the astronomy loop.
But I have a question, is it possibly here in the UK to have a full moon
in
the day ?
Or at twilight (the hour after sunset).

Hope you guys can help, me.
Cheers.
Gary


If you mean a full/very nearly full moon rising in the east just after the
Sun has set in the West, definitely.

Gary McGuinness NO@SPAM.? wrote on Fri, 19 Sep 2003:
I'm not in the astronomy loop.
But I have a question, is it possibly here in the UK to have a full moon in
the day ?
Or at twilight (the hour after sunset).

Yes.

If full moon occurs at sunrise or sunset then not only will it be
visible in twilight, but it will very briefly be visible after sunrise
or before sunset due to the effect of refraction in the atmosphere.

Dave.
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"Gary McGuinness" NO SPAM wrote in message
...
I'm not in the astronomy loop.
But I have a question, is it possibly here in the UK to have a full moon
in
the day ?
Or at twilight (the hour after sunset).

Hope you guys can help, me.
Cheers.
Gary

In twilight, definitely. The full moon rises as soon as the sun sets.

In full daylight, just barely, for 2 reasons:

(1) Refraction makes the sun and moon appear slightly higher than the true
position in the sky. There is enough refraction that if the sun and moon
are directly opposite each other, you can still get them in the sky at the
same time, just barely. When each of them should be exactly cut in half by
the horizon, they both will actually be completely above the horizon (and
grazing it on the bottom edge).

(2) You can fudge on the definition of "full moon." Usually, when we
consider the moon to be full, it is not *exactly* opposite the sun.


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

"Michael A. Covington"
wrote:

In twilight, definitely. The full moon rises as soon as the sun sets.

In full daylight, just barely, for 2 reasons:

(1) Refraction makes the sun and moon appear slightly higher than the true
position in the sky. There is enough refraction that if the sun and moon
are directly opposite each other, you can still get them in the sky at the
same time, just barely. When each of them should be exactly cut in half by
the horizon, they both will actually be completely above the horizon (and
grazing it on the bottom edge).

(2) You can fudge on the definition of "full moon." Usually, when we
consider the moon to be full, it is not *exactly* opposite the sun.

Now I'm confused (ok, I know, easily done, etc)

but doesn't it make a big difference if the Moon is above or below the
ecliptic?

Cheers

Martin

--------------
Martin Frey
N 51 02 E 0 47
--------------

"Mike Dworetsky" wrote:


but doesn't it make a big difference if the Moon is above or below the
ecliptic?


It could make quite a difference. Consider the following example: Imagine
a Full Moon under the following circumstances (FM defined as moment when
diff in longitudes of Sun and Moon is 180 degrees). Think of an observer
right on the Arctic Circle, midwinter noon Dec 21st, and the Moon 5 degrees
N of the ecliptic (ISTR it can get about 5.5 deg either side). The Full
Moon would be circumpolar and above the horizon at due north, the Sun just
above the horizon in the south due to refraction. Even without refraction
the Sun and Moon would both be above the horizon (half the Sun anyways).

So generally the further north or south you are, the more the answer to the
original question is yes.

Mike thanks - it's obvious but had never occurred to me that the lands
of the midnight Sun may also be the lands of the 24 hour Moon.

I'm thinking that it ought to be possible to see a complete lunar
cycle without ever losing sight of the Moon except in the glare of the
Sun. That would be an interesting time lapse film, even if it lacks
the contrast of night..

Cheers

Martin

--------------
Martin Frey
N 51 02 E 0 47
--------------

JRS: In article , seen in
news:uk.sci.astronomy, Martin Frey posted
at Sat, 20 Sep 2003 13:46:01 :-

I'm thinking that it ought to be possible to see a complete lunar
cycle without ever losing sight of the Moon except in the glare of the
Sun. That would be an interesting time lapse film, even if it lacks
the contrast of night..

Since the Moon's orbit's axis is at 5 deg to the Earth's axis of
rotation, ISTM that you can see the Moon for a whole day if above 67 - 5
= 62 deg N, but that you can never see it for a whole month.

OTOH, I sometimes have thought that above 67 + 5 = 72 deg N is special.

At least as regards 62 deg N, perhaps Dave could ask in Norway - or do
we have any readers from northern Scandinavia, Alaska, etc.

Or has anyone got an Orrery?

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
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Dr John Stockton wrote:

Since the Moon's orbit's axis is at 5 deg to the Earth's axis of
rotation, ISTM that you can see the Moon for a whole day if above 67 - 5
= 62 deg N, but that you can never see it for a whole month.

OTOH, I sometimes have thought that above 67 + 5 = 72 deg N is special.

At least as regards 62 deg N, perhaps Dave could ask in Norway - or do
we have any readers from northern Scandinavia, Alaska, etc.

Or has anyone got an Orrery?

My head begins to hurt - but can we have a daytime lunar eclipse?

Well - not us, but eskimos?

Cheers

Martin

--------------
Martin Frey
N 51 02 E 0 47
--------------

"Martin Frey" wrote in message
...
Dr John Stockton wrote:

Since the Moon's orbit's axis is at 5 deg to the Earth's axis of
rotation, ISTM that you can see the Moon for a whole day if above 67 - 5
= 62 deg N, but that you can never see it for a whole month.

OTOH, I sometimes have thought that above 67 + 5 = 72 deg N is special.

At least as regards 62 deg N, perhaps Dave could ask in Norway - or do
we have any readers from northern Scandinavia, Alaska, etc.

Or has anyone got an Orrery?

My head begins to hurt - but can we have a daytime lunar eclipse?

Well - not us, but eskimos?


To get a lunar eclipse, the Moon has to be very close to the ecliptic.
Hence the main way in which the eclipsed Moon could be above the horizon,
while the Sun is also above, is refraction plus the Moon being positioned at
a favourable maximum distance from the centre of the Earth's shadow.
Needless to say, the eclipsed Moon would be quite faint, and at such a low
elevation (about 1 deg) I doubt if it could be visible under these
conditions, but maybe.

Eskimos probably would not need to be invoked; the problem would be similar
anywhere in the world.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

JRS: In article , seen in
news:uk.sci.astronomy, Martin Frey posted
at Sun, 21 Sep 2003 02:06:19 :-
Dr John Stockton wrote:

Since the Moon's orbit's axis is at 5 deg to the Earth's axis of
rotation, ISTM that you can see the Moon for a whole day if above 67 - 5
= 62 deg N, but that you can never see it for a whole month.

OTOH, I sometimes have thought that above 67 + 5 = 72 deg N is special.

At least as regards 62 deg N, perhaps Dave could ask in Norway - or do
we have any readers from northern Scandinavia, Alaska, etc.

Or has anyone got an Orrery?

My head begins to hurt - but can we have a daytime lunar eclipse?

A Lunar Eclipse is a close-to-exact Full Moon that happens when the Moon
crosses the Ecliptic.

In clear skies, a setting full moon should be perfectly visible; so one
could probably see that the Moon became invisible, by shadow, before
setting. If up that early.

Each body is elevated by most of a degree due to refraction. One can
gain another degree, per body, by finding a location 970 m above sea-
level with a sea horizon in the right direction. As the UK in part
exceeds 1250 m, this is not out of the question. GC, or neighbours,
might do better, in spite of NM being coastally-challenged.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.