Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 2014-01-10 12:14:31

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Moon sightings

I saw the moon behind clouds and I think it is an increasing waxing moon of about 50% light, not sure due to clouds.


igloo myrtilles fourmis

Offline

#2 2014-01-18 06:01:02

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

saw full moon yesterday!!


igloo myrtilles fourmis

Offline

#3 2014-01-22 05:14:55

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

yesterday at 5am EST the moon was 8/14's lit up on the left side with the shade-line from 1-oclock to 7-oclock at 72W43E of london.
The left side I believe of the moon was lit up which means its getting smaller now I guess if i remember right, i'm a little dislexic in memory.


igloo myrtilles fourmis

Offline

#4 2014-01-24 02:23:52

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

yesterday morning, thursday, at 5 am EST 72W43N, the moon was about 53% lit up and 47% dark +-5%.
At 8am EST it seemed to be about 51% lit up, but It probably can't change that fast, so I think it was an illusion.
Also as it moved across the sky, the line between dark and light went from 11-oclick to 5-oclock, and then 3 hours later,
it went from 1'-oclock to 7óclock.  (the oclocks are not times, they are positions on a circle)


igloo myrtilles fourmis

Offline

#5 2014-01-24 08:18:55

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: Moon sightings

hi John

When the Moon is in a crescent phase it looks like a C shape from here in the UK (maybe tilted a bit depending on the time).

When I was on holiday in the Galapagos Islands,  the same shape was twisted round so it looked more U shaped.

Once I thought about it, it was fairly obvious, as the lit up bit has to point towards the Sun, and then Sun goes pretty much East -> overhead -> West when you're on the Equator.  Interesting though.

It was around the start of November when Venus was close to eastern elongation, so it was high in the sky when the Sun went down.  But how high!  I've never seen it that high from the UK.  Again it's all to do with the line of the Ecliptic.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#6 2014-01-24 08:39:58

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

Yes!! I've never visited below 25 degrees north, but I have thought about that and imagined that would happen.  That is so cool.  I asked someone who visits Ecuador each year, but she couldn't remember taking note of it.


igloo myrtilles fourmis

Offline

#7 2014-01-24 21:20:28

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: Moon sightings

Travel gives you a whole new perspective on the sky.

My wife is very keen on the Sun.  When we were in New Zealand she was very surprised that the Sun went across the sky the wrong way (right to left).  And we saw Orion in the evening and it looked a bit funny.  Then we realised it was the wrong way up.  Interestingly, it looks almost the same that way (approx. rotational symmetry)

Getting back to the Moon, here's a question for you.  When the Moon is low in the sky, does it look bigger to you than when it is high up?  You can try the Patrick Moore test.  Find a coin that, when held at arm's length, appears the same size as the Moon.  Do the test for a high Moon and a low Moon.  Best at full Moon, but you can still do it when the Moon is nearly circular.  So what's going on there?

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#8 2014-02-06 11:30:10

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

I'll look into that.  Good coin idea.  I might try it this winter but my results may vary more in the spring and summer when I get a higher arc.  I'm at 43 degrees north.   Looks like I'll have to wait a week or two to view this...


igloo myrtilles fourmis

Offline

#9 2014-02-10 12:46:52

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

5:49PM EST, the moon was about 3/4 full or 2/3 or thereabout and a planet I think like Jupiter was about 5 moon diameters to the north of the moon.  Tonight was Monday in the 8th week of winter 2014.


igloo myrtilles fourmis

Offline

#10 2014-02-11 12:36:40

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

7:15PM EST, the moon was about 7/8 full and the unknown Jupiter planet seems to be about 10 moon diameters NW from the moon.  Tonight is tuesday in the 8th week of winter 2014.


igloo myrtilles fourmis

Offline

#11 2014-02-11 20:57:15

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: Moon sightings

hi John,

Jupiter has just gone past opposition when it would be at its brightest and highest in the sky around the middle of the night. So it would rise in the East, stay visible for most of the night, and set in the West.  Have you got a telescope or binoculars ?  If you can hold them steady  you should be able to make out some of Jupiter's moons.

I think we can rule out the other planets.  Venus would be too close to the Sun in line of sight.  Saturn is 'round the other side of the Sun' at the moment and only likely to be seen very early in the morning.  Mars is approaching opposition.  At the moment you'd have to stay up until the early hours to see Mars, but over the next few months will become visible earlier and earlier in the night.  The reddish colour makes Mars an easy ident.

Bob

Last edited by bob bundy (2014-02-11 21:05:58)


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#12 2014-02-12 04:20:51

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

Yes, I have some good binoculars and also a small telescope.  I will check soon if I can see 1, 2, 3, or 4 of the Galilean moons with the small red telescope my late uncle got us when I was little.   Is the opposition word opposite the Earth thru the sun or elseword?


igloo myrtilles fourmis

Offline

#13 2014-02-12 07:33:07

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: Moon sightings

hi John,

When the alignment is SUN, then EARTH, then MARS this is called opposition.  It's the best time to observe a planet further from the Sun than us, because (i) the face pointing towards us is fully illuminated; (ii) the distance is minimum; (iii) the Sun is 'behind' us ie. it's the middle of the night.

For a planet nearer the Sun, (Venus and Mercury) the alignment SUN, then PLANET, then EARTH is no use for observation because (i) the planet would be in the daytime sky; and (ii) the dark side of the planet is facing us.

For Venus the maximum angular separation between the Sun and Venus is about 47 degrees.  That is the angle VES.  This is called elongation.  I was lucky to be in Ecuador on Nov 6th last year when this happened.  The Sun dropped below the horizon and Venus was still high up in the sky and shining brightly.  From the UK the angle is the same but the plane of the ecliptic is much lower in the sky so the height of Venus above the horizon is much less.  If you were looking down from space on the North Pole then the Earth would be rotating anticlockwise.  And so would all the planets around the Sun.  So at that time, Venus would be on the left hand side.  Imagine a line representing the horizon rotating anticlockwise.  First the Sun would drop below the horizon, then later, Venus.  For this reason Venus is called the Evening Star, although of course it is not a star.  When Venus is at elongation on the right, the horizon line cuts through Venus first, before the Sun rises.  At that time Venus is called the Morning Star.

Bob

View Image: planets.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#14 2014-02-13 03:36:43

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

thanks you for the complete explanation.  I understand opposition now.  Has there ever in the history of time been an eclipse of Earth against another outer planet?  Probably not and the sun is so big you might not get an eclipse anyway.


igloo myrtilles fourmis

Offline

#15 2014-02-13 04:24:04

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: Moon sightings

So you're wondering, if you were on, say, Jupiter, (wouldn't recommend it but let's say you're there); then would the Earth ever block out the Sun like the Moon does for us.  A quick guess is no because the Earth isn't big enough but I'll do some sums and come back with a definite answer.

Venus has recently come exactly between the Earth and the Sun, giving rise to a 'transit of Venus' across the face of the Sun.  From the pictures I saw, Venus was much too small to do more than make a black dot as it tracked across.  You could probably 'google' for some pics.

When I was young, one ambition was to be in Cornwall, UK, for a total eclipse.  It was expected during the summer of 1999 so I thought we'd book a summer holiday there.  My wife wanted to go abroad.  So I looked up the track and we ended up in Fuschl, Austria.

Our hotel was right on the track and we had an amazing morning seeing the eclipse perfectly.  smile It was cloudy in Cornwall and they saw nothing sad

In the afternoon, we went for a walk and got caught out by a thunder storm.  But I didn't care about getting wet because I was still on a high from seeing the eclipse.  If you are prepared to travel they are fairly frequent somewhere in the World.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#16 2014-02-13 07:17:23

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: Moon sightings

hi, me again.

The first diagram below shows my approach to this question.  To stand any chance of causing an eclipse, the Sun, Earth and the planet must be in a straight line.  If you divide the Sun's diameter by the distance from the Sun to the planet (SP) you get a measure of the angle subtended by the Sun at the planet.  If you divide the Earth's diameter by the distance between the Earth and the planet (EP) you get a measure of the angle subtended by the Earth at the planet.

If the first is greater than the second, then some of the Sun's disk will be visible even if the Earth is in the way.

The diameters are in Km.  I have included the diameters of the planets just for interest.

Approximations.   The distances are averages as none of the planets orbits in a perfect circle.

The division would not work if the diameters were comparable with the distances across space.  But as the distances are all much greater the division gives a good approximation for the angle in radians.

The second image is the table of calculations.  You can see that none of the results suggests an eclipse would occur.  You would get a transit if the alignment is right.  All the planets orbit the Sun in approximately the same plane.  This seems to be because of the way the solar system developed billions of years ago.  It is called the plane of the ecliptic.  But these orbits are only approximately in the same plane, and the small variations are enough to make transits relatively rare.  eg.  Most times when Venus lies between us and the Sun it is slightly above or below the disk of the Sun so no transit is seen.

Bob

View Image: planetary eclipses.gif View Image: planetary eclipses2.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#17 2014-02-13 08:29:55

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

Wow, that's neat. 
So I guess even Mars wouldn't get totally eclipsed by Earth because of the proportions.
That's cool you visited the eclipse.  I've seen two eclipes of the sun I remember well.
One I went under a small tree along a road and the crescent shapes of light were
thousands in number under the tree's shadow!  Another time I used many polarized
lenses at various turning angles to black out and look for a second at it.


igloo myrtilles fourmis

Offline

#18 2014-02-22 05:58:58

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

At 9am this morning (4 hours ago exactly) I saw the moon about 1/3 lit-up on the left, so waning (viewed from 43 degrees north).
The sun was up and the moon was heading down.


igloo myrtilles fourmis

Offline

#19 2014-03-08 08:23:14

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

Two minutes ago, I just saw a perfect half moon, waxing, now during the day at 3:20PM East Coast USA.


igloo myrtilles fourmis

Offline

#20 2014-06-25 12:29:18

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

on monday june 23rd, i saw a skinny crescent moon, waning to knowledge.


igloo myrtilles fourmis

Offline

#21 2014-07-20 18:47:25

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,565

Re: Moon sightings

july 21:  waning skinny crescent two hours before dawn.


igloo myrtilles fourmis

Offline

Board footer

Powered by FluxBB