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Total Lunar Eclipse
v@mp writes "I noticed a few posts today about space, which reminded me that there will be a total lunar eclipse in North America and Western Europe on Jan. 20. The moon will turn a deep red color for little over an hour around 8 p.m. on the west coast and 11 p.m. on the east coast. I'll see you all "under a blood red sky"--U2. "
Light is bent (refracted) as it passes through a lens. Different wavelengths of light are bent at different angles. Red bends more than blue. The earth's atmosphere acts as a lens. yellow/green/blue/violet light razing the earth during the eclipse are not refracted very much and do not strike the shadowed moon. Orange Red light is bent much more, enough to shine on the eclipsed moon. Hence the moon looks red. This has nothing to do with the content of the atmosphere so the redness is not caused by smog. Cromatic abberation is why telescopes with lenses (refractors) hav an upper limit to how sharply you can focus on an object. because the focal length is different for different colors. Reflector telescopes can form much sharper images because the angle of reflection off of a mirror does NOT change with wavelength.
On CNN, they had some astronomy "expert" explain that the redness of the moon during totality was due to POLLUTANTS in the atmosphere! Puh-leeze. No mention of chromatic abberation. The publich will glaze over with that explanation, but smog? Yeah, they'll buy that! And it'll keep them in PH33R on environmental issues, like the "ozone hole" over Antarctica. Would you call a region of a wall that is a few percent less thick a "hole"? (Not to mention that we're drawing conclusions on global weather trends with a few decades worth of data. "experts" can't even explain the causes of the ice ages.) The scary part is that people will believe this and use it to bash more bad legislation onto all of us. Smog checks for mopeds? lawn mowers? leaf blowers? outboard boat engines? go-karts? Chain-saws? Don't laugh. California wants to do just this to pretty much *anything* with a gas engine in it.
Is anyone out there set up to do astrophotography with a tracking scope and a digital camera like the Kodak DC-2xx series? With a big enough memory card (a 64MB CF would do) you could take full-res photos spaced about 2 minutes apart for the full duration of the eclipse, or 1 minute apart through totality. Would make a cool animation!
--Jim
Your position on Earth relative to the Equator has nothing to do with it. Set up this experiment... Take a flashlight (close to a point source of light, similar to the Sun), turn it on, set it on something (so you can move around without the flashlight) and use it to cast a shadow on the wall. Go to the wall and put a sticky note on the wall in the shadow. Now, no matter where you move in the room, the sticky note will not appear out of the shadow. The angle with which the beam of light impacts the intervening object (the one casting the shadow) does not change. Thus, the position of the shadow does not change. Obviously, unless the sticky note falls off the wall, its position does not change. The simple fact of moving yourself around the room doesn't do anything (other than maybe knock over a chair in the dark!).
Similarly, your position with respect to the Equator will not change the fact that the entire moon will lie within Earth's shadow. That's what is required for a full lunar eclipse.
People in Eastern Europe (different longitude) will not see the eclipse simply because the moon will have set for them already. Remember, if the eclipse starts at 10pm, with totality onset at 11pm, this is 3am and 4am GMT, respectively. Eastern European sites are at GMT + several hours. It will already be daytime, and since a full moon rises at sunset, and sets at sunrise, these people will miss out.
I can agree with your assessment that there is only one moon, however.
Eric
Not to sound religiously aetheist....
:-)
the bible (and indeed many/all religious texts) weave fact into fiction and back around again. Lunar eclipses aren't rare. Probably someone knew about blood red eclipses and thought it sounded pretty good thrown in in the religious sense.
Read Stranger in a Strange Land by Robert Heinlein. That's my bible
--Remove SPAM from my address to mail me
>> Isn't there somewhere in Revelations ...
Actually, it's the book of Revelation.
Singular.
"I watched as he opened the sixth seal. There
was a great earthquake. The sun turned black
like sackcloth made of goat hair, the whole moon
turned blood red" - Revelation 6:12
"The sun will be turned to darkness and the
moon to blood before the coming of the great
and dreadful day of the Lord." - Joel 2:31
--- witty signature
Tons of info on upcoming lunar eclipses, other celestial events, and complete sunrise/sunset calendars (not to mention navigational ephemeris data) are available at the way, way cool page of the Astronomical Applications Dept. of the US Naval Observatory in Washington -- truly the home of the Time Lords.
--
I am quite civilized, and I should be brought a beer immediately. -- Bruce Sterling
your bit about volcanic ash, though, is presumably partially correct -- within certain limits, presumably more dust means more scattering (and hence a stronger red color, since the red component isn't affected nearly as much).
Today is my birthday. Obviously, the moon is turning blood red to mark the dawn of a new era, the era in which I rise to rule mankind. Tonight is my night. Pray that you're on my good side...
-CausticPuppy "Of all the people I know, you're certainly one of them." -Somebody I don't know
Sicne the Moon is in Gemini, you're in a good situation because you can take longer exposures without getting trails. For a 50mm shot, my guess is anything under 15-20 sec should give you no trails (using a narrower-angle lens will decrease this tremendously!), but even when eclipsed the Moon might be still bright enough that you'll be using very short exposures. (Unfortunately my copy of Gordon's book is at the office, and I"m not!). Of course if you're using a telescope with tracking, it's not as much of an issue. I've only done still tripod imaging (which is fun all by itself). But be forewarned, even though the Moon looks HUGE, with a 50 mm lens, the actual lunar disk will only have a diameter of about 3 mm on the film!
Dickinson and Newton recommend for 400 speed film (I recommend SLIDE film over print film!) at f/8, an exposure time of 1/250 s at partial phases (after ingress), to 1/4 s during ingress near totality, to 1 to 10 seconds once totality starts, up to 100s for the deepest parts of the eclipse (and probably if the Moon is at perigee). Of course for exposures that are VERY long, you'll need to track the Moon to offset sidereal motion. But at a declination of 20 degrees North, as I said you can probably get up to 15 seconds without too much distortion (for a 50 mm lens).
Of course, in Boston, it's snowing.
But the next lunar eclipse visible in North America is less than a year away (Jan. 9, 2001).
Despite the fact that a solar eclipse and a lunar eclipse are completely different things, and staring at the full moon would not normally cause damage, it is important to remember that staring at an eclipse can damage your eyes.
More frighteningly, lunar eclipses emit deadly "lunar rays" which affect your brain and make you stupid enough to try to watch it through a welder's mask instead of binoculars.