No one has to apologise for the truth!

Sometimes it seems (for what reason ever) that irony is not detected when I try. Maybe as a non native English speaker I don’t get the correct twist.

Andre

Ah, I understand now. Please accept my apologies.

“AbdreH: “…You can’t see the Sun and stars in full daylight…”

Obviously you can see the sun in full daylight. After all the Sun is what makes it daylight. But I think I know what you mean.”

Sorry, but in did not say this.

Mark Martin:

“There is no question that stars can be photographed in the lunar sky. The problem is photographing simultaneously with the bright lunar landscape, astronauts, etc. The exposure settings for one are not optimal for the other. Notice, please, that there are no stars in photographs taken from the space shuttle under similar conditions. Under conditions optimized for star imaging, they can be photographed. Star imaging is in fact routinely used by remote spacecraft for navigation.

Notice also that BA’s photo above was taken well after the Sun had set, and that there are only a very few of the brighter sky-objects (the Moon, Jupiter, Antares) registered on it. The many other stars in that field of view didn’t show up at all, because the exposure wasn’t adequate to register them.”

Thanks for the explanation. But I knew this already. I tried to be ironical.
I was really surprised Jupiter can be seen on the photo although the moon seems to be some magitudes brighter and bigger. Therefore my thinking was mayby some HB may claim this.

Andre

I recently bought a new camera (my first digital, woohoo!), and its maximum exposure is 60 seconds. I tried this out (first light, I guess) recently, and got a reasonable pic of Ursa Major with the camera set to wide-angle, but zoomed in (12x optical zoom), all the stars were curved lines. I had not realised that the 0.25 degrees the Earth turns in a minute would be enough to streak the stars across my image.

For a typical camera (say with a 35 mm objective), is there an optimal compromise between exposure time and keeping the stars as point-like sources (assuming perfect seeing)?

Thanks for the explanation, now even I got it. What really puzzled me, I think, is the off-hand way the statements about the sun moving through the stars in the course of the year are usually made. To me it sounded like something totally obvious, something you can really see day for day (like the sun rising and setting or the stars moving in an arc across the sky at night), when in reality it is a rather abstract concept (at least to me), that can not easily be observed (meaning “be looked at”) from earth.

Phil said the sun makes a big circle in the sky over the course of a year, called an ecliptic. The analemma is the path that the sun takes over the course of a year at a fixed time of day, and this is clearly not a circle (as seen in several APOD photos). So I remain confused, but not yet to the point where I’ll look it up, as I’ve been working for over 20 hours now and it’s time for bed.

As I recall (and I may be wrong here – operating from fuzzy memory) the prevailing theory of the moon’s ecliptic tilt is that the moon was indeed created by a massive impact into the then very young and hot Earth. This impact was from a large object with a different ecliptic than the Earth. Think of a comet orbit. The ejecta from the impact (the moon) achieved orbit of the Earth – and since the impactor was off ecliptic the ejecta was as well. The 5 degrees is just concidental… it could have just as easily been 25 degrees. It’s like a game of billiards (only in 3 dimensions) – in order for a ball to go straight you have to hit it perfectly through it’s center. if you are off by just a bit the target ball is propelled to one side or the other.

Not sure I’ve been terribly clear there. Sorry if I’ve muddled things up.

This means that the position of Jupiter is roughly equivalent to the ecliptic, and if the moon was 5 degrees below Jupiter, then it was 5 degrees below the ecliptic – meaning it was as far down as it could go.

Cheers, that had me confused too.

But that only works if you’re far North, correct? e.g. If you live near the equator, the ecliptic is an arc over your head. Then the Moon, when it’s furthest South, would appear to the left of Jupiter?

The Earth-Moon may be considered a double-planet, but only because of their mass-ratio, not because the “Moon is taking its marching orders from the Sun”. The latter is entirely due to the fact that the Moon’s orbit is quite large and its orbit is in fact strongly perturbed by the gravity of the Sun. Indeed, consider the irregular satellites of the Jovian planets: all of these irregulars “take their marching orders from the Sun”, and yet we would not consider, say, Jupiter and Paisphae to be a double planet. In general, irregular satellites have inclinations (measured w.r.t. the planets’ orbital plane) that are far from zero. The Moon’s 5 degree inclination is indeed quite large.

Cheers.

Well… most of it…

http://www.midwestrocklobster.com/ugly/ugly3_lg.gif

Yes, it’s real. Won the Ugliest Dog contest somewhere. Died recently.

If so, I’d expect the Moon to orbit in a plane with the Earth’s equator, but since we know that’s 23.5 degrees (from an earlier post, if we forgot it from science class) off the elliptic, if these theories were true, wouldn’t we expect the Moon to orbit just as far off the plane as our axis?

So I guess I’m curious if the prevailing attitudes about the formation of the moon have changed, and why 5 degrees, not close to 0 or 23.5.

Obviously you can see the sun in full daylight. After all the Sun is what makes it daylight. But I think I know what you mean.

Reminds me, though, of the woman who said, “If the Sun is a star how come you can’t see it at night. ” And see was serious!

Because as Phil says: “The Earth orbits the Sun (with me so far?). Over the year, that means it looks like the Sun makes a big circle in the sky relative to the stars. We call that path the ecliptic. The major planets all orbit the Sun in roughly the same plane, so they stick to the ecliptic too. Not exactly on it, but pretty close.”

This means that the position of Jupiter is roughly equivalent to the ecliptic, and if the moon was 5 degrees below Jupiter, then it was 5 degrees below the ecliptic – meaning it was as far down as it could go.

There is no question that stars can be photographed in the lunar sky. The problem is photographing simultaneously with the bright lunar landscape, astronauts, etc. The exposure settings for one are not optimal for the other. Notice, please, that there are no stars in photographs taken from the space shuttle under similar conditions. Under conditions optimized for star imaging, they can be photographed. Star imaging is in fact routinely used by remote spacecraft for navigation.

Notice also that BA’s photo above was taken well after the Sun had set, and that there are only a very few of the brighter sky-objects (the Moon, Jupiter, Antares) registered on it. The many other stars in that field of view didn’t show up at all, because the exposure wasn’t adequate to register them.

Every month (as compared to every year with the sun) the moon sets at a different point on the horizon, SW to NW. This also coincides with the phase of the moon. Full moons set far to the NW, fingernail moons to the SW. (I’m still looking for the new moon…)

Why is there a correlation? Just chance? I doubt it.

Also BABlogger, how did you know that the moon had dipped a far as it could go based on its positioni vi a vis Jupiter?