Starship Asterisk*

by **Dr. Skeptic** » Sat Apr 19, 2008 1:44 am

BMAONE23 wrote:Only just thought of it yesterday but it isn't clear today to try it (of course, I would try it during the day because the paper would be dark at night)

I'll be interested in your results.

PS: As a thought, you might also try your experiment using black paper.

by **BMAONE23** » Fri Apr 18, 2008 5:07 pm

Only just thought of it yesterday but it isn't clear today to try it (of course, I would try it during the day because the paper would be dark at night)

by **Dr. Skeptic** » Fri Apr 18, 2008 3:32 pm

BMAONE23 wrote:Take a bright white piece of paper and, using a hole punch, create a viewing area through the middle of the page. Hold this white paper up to the moon and adjust until the Moon fills the Hole Is the moon Blue, Or White?

Is this something you've tried?

by **BMAONE23** » Thu Apr 17, 2008 1:59 pm

Take a bright white piece of paper and, using a hole punch, create a viewing area through the middle of the page. Hold this white paper up to the moon and adjust until the Moon fills the Hole Is the moon Blue, Or White?

by **Dr. Skeptic** » Thu Apr 17, 2008 1:17 pm

The mind has incredible control over color perceptions:

http://en.wikipedia.org/wiki/Image:ColourIllusion2.jpg

The brain is very good at color compensation for "relative" changes in perceived colors, making the brain vary bad at determining "empirical" values of shades, tones and hues.

http://en.wikipedia.org/wiki/Image:Grey ... lusion.PNG
(I've always liked this one.)

So the "Blue Moon" looks "blue" relative to the over all spectrum of light entering the eye, if you were to look at the same Moon at the same time through a high powered telescope (removing the ambient light) it would appear to be slightly brown.

Years ago I was involved in cinema work, to keep continuity in colors, the cameras constantly need filters changed from indoor to outdoor, even room to room - even the smartest cameras can't preform color correction as well as our brains.

by **Qev** » Thu Apr 17, 2008 7:35 am

Sputnick wrote:Also - why is a normal daylight moon white? If the sky is blue because of sunlight scattering off air molecules, and the moon shines because of reflected sunlight, the moon should appear blue all the time.

I imagine the daylight moon does have a bluish cast due to the diffuse sky-glow, but considering how we humans perceive colour, it seems white in comparison to the surrounding sky.

I'm not sure how to quantify how much of the redness of a sunset comes from Rayleigh scattering and how much is dust... I suppose the simplest measure would be to compare sunset to sunrise. Sunsets tend to be redder than sunrises due to the dust and volatiles stirred up into the atmosphere during daylight hours.

by **astrolabe** » Thu Apr 17, 2008 2:54 am

P.S. The use of an UV filter for snow or sand and the higher elevations like the mountains is a definite must.

by **astrolabe** » Thu Apr 17, 2008 2:45 am

Hello Sputnick.

I'm not going near the Blue Moon issue but as a photographer I can say that the the dynamic involving blue wavelengths being reflected or absorbed by our atmosphere is true as stated.

In the daytime, especially at midday, the use of an UV filter is strongly recommended as film (like B&W) is sensitive to blue light and one can end up with blocked out white skies where blue would be expected. The filter is not necessary for sunrise or sunset photos because of the absorption of blue light at the low sun angle.

When I logged in this time I almost didn't catch that I had spelled my moniker with two esses- what an eye opener THAT was![/b]

by **bystander** » Tue Apr 15, 2008 8:50 pm

http://en.wikipedia.org/wiki/Diffuse_sk ... tion#Color

The sunlit sky appears blue because air scatters short-wavelength light more than longer wavelengths. Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light. The result is that the human eye perceives blue when looking toward parts of the sky other than the sun. Near sunrise and sunset, most of the light we see comes in nearly tangent to the Earth's surface, so that the light's path through the atmosphere is so long that much of the blue and even green light is scattered out, leaving the sun rays and the clouds it illuminates red.

http://en.wikipedia.org/wiki/Blue_moon# ... _blue_moon

The most literal meaning of blue moon is when the moon (not necessarily a full moon) appears to a casual observer to be unusually bluish, which is a rare event. The effect can be caused by smoke or dust particles in the atmosphere, as has happened after forest fires in Sweden and Canada in 1950 and, notably, after the eruption of Krakatoa in 1883, which caused the moon to appear blue for nearly two years.

by **Sputnick** » Tue Apr 15, 2008 8:20 pm

BMA123 - Yes -- there is a swimming pool in my backyard .. but it has a blue liner, probably to hide the water pollution which permeates every drop on the earth's surface.

Bystander's post is informative - however, sunrises and sunsets can be coloured .. some of this is pollution (simple dust for instance) .. how much colouring is due to wavelength absorbtion due to the increased distance the light travels through the atmosphere .. or does light travel increased distances at sunrises and sunsets? I'll have to draw a diagram for myself .. although I think I should examine some water-coloured vodka first.

by **Sputnick** » Tue Apr 15, 2008 8:09 pm

Bystander -- In my experiences the sky has been exceptionally pollution free during Blue Moons. In your opinion why does the sky need no pollution to be blue (the sky often turning green or orange etc when polluted) but the sky in which the blue moon shines does need pollution? Please explain even though I will still assert the Blue Moon needs no pollution because of my first hand experiences. Also .. have you seen Blue Moons in Oklahoma? At least we have gotten into the physical realities now rather than silly calendars leaping all over each other.

Also - why is a normal daylight moon white? If the sky is blue because of sunlight scattering off air molecules, and the moon shines because of reflected sunlight, the moon should appear blue all the time.

by **BMAONE23** » Tue Apr 15, 2008 7:31 pm

I believe the sky is blue because the gasses comprising it tend to absorb ALL wavelengths of light except the blue hues so the blue hues are reflected around or scattered in the atmosphere.
Did you know hae George Carlin was incorrect in his assertion that "There is no Blue Food?" He states that even 'Blueberries" are purple, which is true. But there is a "Blue" food, and we can't survive for more than a couple of days without, Water is blue...Look at glacial ice...Blue, clear ocean water...Blue, Fill you're white bathtub...Blue, Fill your white plastered swimming pool...Blue!

by **bystander** » Tue Apr 15, 2008 7:25 pm

Sputnick wrote:Wonderful! At least we have agreement that the moon can actually be seen as if coloured blue. Amazing! Agreement in a discussion forum! Well done! I am encouraged greatly.

However, I can not agree that a Blue Moon would absolutely require pollution as the source of its hue as the natural colour of the unclouded sky was blue before pollution .. and what we are seeing during a Blue Moon in times of non-pollution is (probably) not the moon's colouring, but the sky's natural colouring. I think atmospheric clarity is the prime factor in times of non-pollution, allowing us to see the sky's natural colour because of the brightness of the moon. Snow seems to be another factor: perhaps the snow reflects the sky's natural colouring as far as the moon (as a contributor here has suggested but which I at first thoughtlessly discounted). If the sky's natural colour were reflected by the snow onto the moon, the moon would appear blue if seen by someone positioned beyond the atmosphere.

Can someone here, a professional hopefully, tell me if the sky's natural colouring is blue because of light refected off the oceans? If not, why is the sky blue?

A casual survey conducted by me today confirms the rarity of people who have seen Blue Moons - even among the white-haired population who have lived long the number is amazingly low.

The sky is blue because of the Rayleigh scattering of sunlight by air molecules. Visually blue moons are blue due to the reflection of light off of dust or smoke particles (pollution) in the air (Mie Scattering???), somewhat similar to blue relection nebula. Large bodies of water are also blue because of scattered light.

by **Sputnick** » Tue Apr 15, 2008 6:21 pm

All the Roman church needed to do to set Easter in its calendar was to copy the Jews in their Passover as the original Easter occured during Passover, and as the Jews never entered the era of confusion and ignorance known as the dark ages.

Moderator Nereid - please note that I am responding to a post on the timing of moons .. not trying to originate a discussion on religion.

by **Sputnick** » Tue Apr 15, 2008 6:13 pm

Wonderful! At least we have agreement that the moon can actually be seen as if coloured blue. Amazing! Agreement in a discussion forum! Well done! I am encouraged greatly.

However, I can not agree that a Blue Moon would absolutely require pollution as the source of its hue as the natural colour of the unclouded sky was blue before pollution .. and what we are seeing during a Blue Moon in times of non-pollution is (probably) not the moon's colouring, but the sky's natural colouring. I think atmospheric clarity is the prime factor in times of non-pollution, allowing us to see the sky's natural colour because of the brightness of the moon. Snow seems to be another factor: perhaps the snow reflects the sky's natural colouring as far as the moon (as a contributor here has suggested but which I at first thoughtlessly discounted). If the sky's natural colour were reflected by the snow onto the moon, the moon would appear blue if seen by someone positioned beyond the atmosphere.

Can someone here, a professional hopefully, tell me if the sky's natural colouring is blue because of light refected off the oceans? If not, why is the sky blue?

A casual survey conducted by me today confirms the rarity of people who have seen Blue Moons - even among the white-haired population who have lived long the number is amazingly low.

by **bystander** » Tue Apr 15, 2008 2:37 pm

The most common reference to blue moon is folk lore. See Asterisk and Wikipedia references above. BTW: a visually blue moon requires some pollution.

Wikipedia -> Blue Moon

The term blue moon is commonly used metaphorically to describe a rare event, as in the saying "once in a blue moon". Early English used the term as an absurdity or impossibility.

Blue moon is also a name given to an extra full moon during a year. Most years have twelve full moons, which occur approximately monthly. However, each calendar year contains those twelve full lunar cycles plus about eleven days to spare. The extra days accumulate, so that every two or three years there is an extra full moon. On average, this happens once every 2.72 years, and different definitions place the extra moon at different times. The extra full moon is called a blue moon.
Folklore gave each moon a name according to its time of year. A moon that came too early had no folk name and was called a blue moon.

The Farmer's Almanac defined blue moon as an extra full moon that occurred in a season (which would normally have three full moons). If a season had 4 full moons, the third full moon was called a blue moon.

The most common modern blue moon definition is the second full moon in a calendar month. This was a misinterpretation of the Maine Farmer's Almanac in 1946 that became commonly accepted and was discovered to be erroneous in 1999.

On rare occasions, atmospheric disturbances give the Moon a bluish coloring.

Asterisk -> Tonights Sky -> blue moon

BMAONE23 wrote:Blue Moon is a term used to describe the 2nd full moon in a single calendar month. If, during leap year, the full moon falls on Feb 1, then Feb 29th will be a Blue Moon.
Actually, that was a misinterpretation of the Farmers Almanac in 1946 that became common usage. It was discovered to be erroneous in 1999. The original meaning from the Farmers Almanac is the third full moon within a season containing four. Another meaning is the 13th full moon within a year. Either will happen about every 2.72 years.

http://en.wikipedia.org/wiki/Blue_moon
http://www.skyandtelescope.com/observin ... 04131.html
http://www.skyandtelescope.com/observin ... 05141.html

There will be no Calendar Blue Moon this year as there are only 12 full moons this year (one per month). Using the Almanac seasonal definition, the full moon on Feb 21, 2008 was a Seasonal Blue Moon (winter started Dec 21, 2007). The last Triskaideka Blue Moon (13th in a year) was Dec 24, 2007.

http://eclipse.gsfc.nasa.gov/phase/phase2001gmt.html

by **neufer** » Tue Apr 15, 2008 2:33 pm

Sputnick wrote:Bystander,

Would you please differentiate yourself outstandingly from most contributors to these types of discussion groups by explaining the reasons for your statement? I'm very interested in your thought processes, because having lived in Canada all of my life, and now being over 60 years old, and having seen two Blue Moons, and having seen a strong and clear Blue Shadow effect once, I know these definite facts: a Blue Moon is called a Blue Moon; most people are not aware of their existence because they live outside of regions where it seems Blue Moons can be experienced (I'm surprised you don't get them in Oklahoma .. but perhaps air pollution is too great) or because they spend their lives in front of a television set; and they believe that 'once in a Blue Moon' is a generalized term for rarity originating somewhere unknown (possibly a cheese factory?)

It is probably air pollution (in the form of Canadian forest fires or even dust blown from distant Asian dust storms) which allows you to see a "blue moon" in Canada:

<<The most literal meaning of blue moon is when the moon (not necessarily a full moon) appears to a casual observer to be unusually bluish, which is a rare event. The effect can be caused by smoke or dust particles in the atmosphere, as has happened after forest fires in Sweden and Canada in 1950 and, notably, after the eruption of Krakatoa in 1883, which caused the moon to appear blue for nearly two years.>>

http://en.wikipedia.org/wiki/Blue_moon
...................................................
<<The earliest recorded English usage of the term "Blue moon" was in 1528 in a pamphlet violently attacking the English Clergy, entitled Rede Me and Be Not Wrothe [Read me and be not angry]: "Yf they say the mone is belewe / We must beleve that it is true" [If they say the moon is blue, we must believe that it is true].

Some interpret this "Blue Moon" as relating to absurdities and impossibilities,[3] and a similar moon-related adage was first recorded in the following year: "They would make men beleue ... that þe Moone is made of grene chese". "They would make men believe ... that the moon is made of green cheese".

An alternative interpretation uses the other meaning of "belewe" (which can mean "Blue", or "Betrayer") The church was responsible for the calendar and used the complex computus to calculate the most important date of Easter - which is usually the first Sunday after the Egg moon. Lent falls before Easter, and the Lent moon (late Winter moon) always falls before the Egg moon (early Spring moon). The Clergy were responsible for telling people when it was Lent - it was critical to celebrate the trials and resurrection of Christ at the correct time. Every 2 or 3 years the Lent and Egg moons would come too early, the Clergy would have to tell people whether the moon was the Lent moon or a false one - they may have called this a Betrayer moon.>>

by **Sputnick** » Tue Apr 15, 2008 2:22 pm

Bystander,

Would you please differentiate yourself outstandingly from most contributors to these types of discussion groups by explaining the reasons for your statement? I'm very interested in your thought processes, because having lived in Canada all of my life, and now being over 60 years old, and having seen two Blue Moons, and having seen a strong and clear Blue Shadow effect once, I know these definite facts: a Blue Moon is called a Blue Moon; most people are not aware of their existance because they live outside of regions where it seems Blue Moons can be experienced (I'm surprised you don't get them in Oklahoma .. but perhaps air pollution is too great) or because they spend their lives in front of a television set; and they believe that 'once in a Blue Moon' is a generalized term for rarity originating somewhere unknown (possibly a cheese factory?) I've now read your APOD references, but wonder if possibly you are aware of another name for the atmospheric phenomena which does indeed happen in Northern Canada, and perhaps other places as well.

by **bystander** » Tue Apr 15, 2008 2:04 pm

Blue moon is really not a reference to the atmospherical phenomenon in Canada to which you refer.

The Asterisk* Forum Index -> Tonight's sky -> blue moon
http://asterisk.apod.com/vie ... =blue+moon

by **Sputnick** » Sun Apr 13, 2008 1:50 am

Up here in Canada the moon actually turns blue on certain cold, clear winter nights. It's rare but I've seen two - with blue shadows another time. Atmospheric conditions have to be just right - it's exceptionaly beautiful. The first time I saw it I thought I was having a flashback - blue snow - blue shadows - very blue moon. I have an artistic rendition of a Moose 'frozen' by the spotlight of a blue moon. "Once in a blue moon" comes from people who knew.

by **Leaves** » Sat Jul 31, 2004 1:54 pm

http://apod.nasa.gov/apod/ap040731.html

I will try to track the source for this, but there were calendars printed in
early last century which colored the moon blue if it was the second one in
the same calendar month. Don’t know if this was a result of term blue moon,
or the derivation for the term. The first moon was always colored red.

Rudy

Starship Asterisk*

Blue Moons (APOD 31 Jul 2004)

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