The moon.......n a star

[daddy diablo]

I've been wanting to post this for forever....havent had a chance to do so till now.

On the 18th of this month, the moon and a star were positioned in what looked like....hell, i don't know. Anyone out there saw it?

I've attached the pictures i took, but my camera phone isn't very strong, so the clarity is rather off. the two pics were taken three hours apart - there was very little change in their relative positions.....after that, cloud cover blotted the sky. couldn't keep track on the moon any longer.

Would like to know what star (planet) was in that position that evening.......this was the sky above Nairobi, Kenya between 1930hrs and 2230hrs.

[Waspie_Dwarf]

The object was the planet Venus. Venus is the third brightest object in the sky after the Sun and Moon and this is why this was so obvious. From your location the two came very close together, but from much of Europe the Moon actually passed in front of Venus.

When the Moon passes in front of a star or planet (or a planet on asteroid passes in front of a star) it is known as an occultation. These are very common for the Moon, for example it occulted Saturn on 2^nd March this year, and it frequently occults bright stars. They are less common for planets and asteroids.

Occultations are useful as precisely timing when the star disappears and reappears can give accurate information as to the exact orbit and diameter of an object. This is not so important with the Moon as we have more direct methods of measurement, but can be extremely useful with asteroids.

The rings of Uranus were discovered in 1977 when it occulted a star. The star flickered repeatedly both before and after it was occulted by the planet's disc. Astronomers concluded that the only possible explanation for this was a set of rings, a conclusion that has now been confirmed by images from the Voyager 2 spacecraft and the Hubble Space Telescope.

Edited June 29, 2007 by Waspie_Dwarf

[daddy diablo]

Hey waspie. thanks a lot. had been dying of curiosity trying to figure out what i saw......hardly anyone saw it, and were saying that i was being delusional (with edited pics and all).

again, thanks.

[Waspie_Dwarf]

Hey waspie. thanks a lot.

Glad I could be of help. Sadly it was cloudy for me in London so I didn't get to see anything.

[Picturesque Orion]

If you have trouble knowing wich one is Venus then just follow this steps:

1. As Waspie said, Venus one of the brightest of them all.

2. When you look up at the evening sky you can notice that stars flicker, very lightly but they do, but planets don't flicker, the light from planets is continous.

3. Venus is know as the morning star and the evening star becuase it is one of the first you see before sunrise and after sunset.

Cheers.

[Waspie_Dwarf]

2. When you look up at the evening sky you can notice that stars flicker, very lightly but they do, but planets don't flicker, the light from planets is continous.

This is a reasonable rule of thumb but it is not always true. The flickering is caused by movement of the atmosphere. Stars tend to flicker more than planets because they are effectively point source of light where was the brighter planets, Venus, Mars and Jupiter have appreciable disks (although too small to be discerned by the naked eye). However if the atmosphere is turbulent enough planets will flicker too. On a very still night the stars will flicker very little.

3. Venus is know as the morning star and the evening star becuase it is one of the first you see before sunrise and after sunset.

Cheers.

This is true but slightly ambiguous. Venus orbits the Sun closer than we do so it can never be too far away from the sun in the sky. It can never be more than 48^o from the Sun. This means that it can be visible up to 3 hours before or after sunset.Where the above statement is slightly misleading is where it says, "one of the first you see before sunrise and after sunset". Depending on where it is in it's orbit it may be visible before sunset or after sunset but never both on the same day. Another interpretation of "one of the first you see before sunrise and after sunset" is the fact that because it is so bright it often becomes visible in twilight before stars are visible. Jupiter is also considerably brighter than any stars and so could be confused for Venus during twilight.

Edited June 29, 2007 by Waspie_Dwarf
to change the tone of the post. It came across more argumentative than I had intended. I was trying to eloborate on Ghostkol's post rather than say he was wrong (which he isn't).

[Harte]

This is a reasonable rule of thumb but it is not always true. The flickering is caused by movement of the atmosphere. Stars tend to flicker more than planets because they are effectively point source of light where was the brighter planets, Venus, Mars and Jupiter have appreciable disks (although too small to be discerned by the naked eye)...

In your vein of agreeing while commenting to the contrary ( ) I have to say here that one actually can discern both Jupiter and Venus as discs. It helps if they are almost full (but not quite) and if they are particularly close to the Earth. If they are showing too much shadow (based on their orientation to both the Earth and the Sun, "crescent" IOW,) they are very difficult to see as anything other than points. But they do have a slightly yellowish tint, more like eggshell, really, than stars, which are so white they are almost blue.

Takes some staring to see this.

Harte

[Waspie_Dwarf]

In your vein of agreeing while commenting to the contrary ( ) I have to say here that one actually can discern both Jupiter and Venus as discs. It helps if they are almost full (but not quite) and if they are particularly close to the Earth.

It is impossible for Venus to be both "almost full" AND "particularly close to the Earth". The very fact that it orbits closer to the Sun than us means it can only show a full disc when it is on the opposite side from the sun to us and, consequently is only a thin crescent when particularly close to the Earth (at its closest to the Earth we would be observing its night side only). It is also very difficult to observe Venus at all when nearly full as it will appear to be close to the Sun in the sky and will only be above the horizon in daylight. Hence the conditions which you claim are necessary to observe Venus as a disk never actually happen.

It is true that a few people with exceptional eye site claim to be able to see Jupiter as a disk but this is far from normal. Jupiter being further from the sun from us, always appears full or nearly full

Edited June 30, 2007 by Waspie_Dwarf

[Harte]

It is impossible for Venus to be both "almost full" AND "particularly close to the Earth". The very fact that it orbits closer to the Sun than us means it can only show a full disc when it is on the opposite side from the sun to us and, consequently is only a thin crescent when particularly close to the Earth (at its closest to the Earth we would be observing its night side only). It is also very difficult to observe Venus at all when nearly full as it will appear to be close to the Sun in the sky and will only be above the horizon in daylight. Hence the conditions which you claim are necessary to observe Venus as a disk never actually happen.

It is true that a few people with exceptional eye site claim to be able to see Jupiter as a disk but this is far from normal. Jupiter being further from the sun from us, always appears full or nearly full

It was Jupiter I was thinking of then, I guess.

The crescent of Venus is certainly visible. I've seen it. But It's not all that thin when I've seen it (I don't exactly look for it all the time - maybe I've seen it once every two or three years since I first noticed it.) My eyesite isn't "exceptional," not as far as I know anyway.

Point is, you can discern a disc when looking at planets, some planets anyway. Try it sometime. Squinting might help.

Harte

[Waspie_Dwarf]

Excuse my scepticism regarding your claims here Harte, but initially you made a claim that Venus is best visible when it shows a nearly full disk:

It helps if they are almost full (but not quite) and if they are particularly close to the Earth.

And is very difficult to discern a crescent:

If they are showing too much shadow (based on their orientation to both the Earth and the Sun, "crescent" IOW,) they are very difficult to see as anything other than points.

However when it is pointed out this is impossible your eyesight miraculously improves and just one post later you can see the crescent of Venus:

The crescent of Venus is certainly visible.

Now there is some discussion amongst amateur astronomers as to whether the crescent of Venus can be seen with the naked eye; this link will give you some information on an experiment that one astronomer carried out to see if he could determine the crescent (the results were indeterminate).

So whilst it may just be possible to see the crescent of Venus, if it is possible then it is certainly not as easy as you would suggest (even highly experienced astronomers can't agree whether it is possible or not).

What worries me even more about your claims is that those amateur astronomers that believe they can see the crescent of Venus believe they can do so just before or after inferior conjunction. This is the time when Venus shows it's narrowest crescent. Unfortunately for your claims this is exactly when you say you haven't seen it:

I've seen it. But It's not all that thin when I've seen it (I don't exactly look for it all the time - maybe I've seen it once every two or three years since I first noticed it.)

Now I am not trying to imply any dishonesty on your part, but your story is so full of inconsistencies and contradictions that I have to ask; are you sure that you are not mistaken?