Basic Astronomy Questions

[Mr Q]

This would be a reason for seeing a bright object near the horizon as red, not blue (as in red sunsets etc). I can't think of a reason for a blue lunar eclipse, so please tell us your answer Mr Q!

I was informed by several media broadcasts that this particular eclipse was going to appear blue a day before its event. The reason given was that the very large forest fire in eastern Canada, that had been burning for several weeks, was the cause. The fire's smoke occasionally reached the ground here in southern New England and the night of the eclipse, the smokey haze was the reason for the blue color.

What was not said was that, was the light going through the smokey atmosphere locally or was the Sun's light actually causing the Moon's bluish color directly. My guess is the former because otherwise, the whole Earth would have to be cloaked in a smokey haze, which it was not. One news broadcast mentioned a previous volcanic eruption that did cloak the Earth's atmosphere but I never heard of anyone else along the eclipse path that reported a blue color. So I assumed it was a regional event.

The puzzle comes up as to how the smoke filtered out the light except for the blue part of the spectrum. My guess is it had to do with the size of the smoke particles. The smoke in the sky (a definate haze) here was a bluish gray for several weeks on most days as the normal NW air flow carried the smoke high aloft over my area. The Moon was about 25 degrees above the true horizon here during the eclipse, making the reflected Moon's light all the more blue as the light traveled through a denser layer of smokey atmosphere.

But the Moon was a definate blue color and just how (the cause) it was, I was never satisfied

[Mr Q]

Many years ago I watched an occultation of the Pleiades by the Moon. The stars in my 10" looked awesome as they winked off and on as they passed behind mountain peaks on the Moon's lit limb. The show lasted some 15+ minuets.

So my question is - when and where in the U.S. will the Moon again occult the cluster?

[OliverP]

Many years ago I watched an occultation of the Pleiades by the Moon. The stars in my 10" looked awesome as they winked off and on as they passed behind mountain peaks on the Moon's lit limb. The show lasted some 15+ minuets.

So my question is - when and where in the U.S. will the Moon again occult the cluster?

I did a search for the next lunar occultation with the Pleiades and I found out that is likely to happen for a period of about 6 years, every 18.6 years. This is because this is the time when the moon is at the correct angle to pass through it. Since the last period was in 2004-2010 by my calculations the next one should be starting around 2023, going to 2029 ish.

So I'm afraid you won't be able to see another occultation for a few years but there should be a few chances in about 11 years from now. Sorry I can't be more exact.

Also if you want to find more exact dates you could go on stellarium (its free to download if you haven't got it) and locate the Pleiades, fix the screen on them and fast forward very fast until they are occulted.

Sources: http://www.space.com/1830-moon-hide-beautiful-star-cluster.html

PS thanks for your explanation for the eclipse question. That certainly had me puzzled!

[FraserClarke]

But the Moon was a definate blue color and just how (the cause) it was, I was never satisfied

Is it not just that the moon is being illuminated by light reflected off the Earth, which is quite blue on account of having lots of oceans...

[OliverP]

Is it not just that the moon is being illuminated by light reflected off the Earth, which is quite blue on account of having lots of oceans...

That could be something to do with it but it is unlikely to have a very big impact as the earth does not reflect that much light, and the light that is reflected has been transmitted from the sun originally so it will be pretty faint (due to the inverse square law).

When the earth is illuminating the moon we get what is called earthshine, which is pretty faint anyway. Furthermore, the moon is in the shadow of the earth so there will be very little reflected light off the earth as it would be from the earths night side.

Overall, a good idea, but pretty unlikely.

[FraserClarke]

Hmmm, think I misread the first question as being on a solar eclipse rather than lunar eclipse. For a lunar eclipse, I agree that Earthshine is unlikely to be a contributor.

[Ronnie67]

Some good reading on here