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Windows 7: A Possible Naked-eye Comet in March, A Better One in December.

21 Nov 2013   #71
Anak

Microsoft Community Contributor Award Recipient

Win 7 Home Premium 64bit Ver 6.1.7600 Build 7601 - SP1
 
 

I hope ISON is better in December also.

Venus's apparent magnitude can fluctuate in brightness from a low of -3.5 to a high of -4.4 depending on the percentage of illumination (It's phase like the Moon's) and its distance from the Earth, these two factors hold true for any of the Planets in our Solar System because the planets reflect light, albedo a third factor.

Venus has all three factors going for it making it a spectacular sight in the evening sky.

Star magnitudes are another matter, they still use + or - values, mostly +, but create their own light.
Stellar Magnitudes

Don't forget, magnitudes work in the opposite. A minus value (-) is brighter than a plus value (+)
The astronomical magnitude scale

Stellarium has Venus at -4.28 today, Saturn at 0.76
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21 Nov 2013   #72
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

The magnitude scale had always been a stick point with me. Why not make it similar to the decibel scale, larger number means louder noise and an increase of one whole DB number is a 10 fold increase from the next lower number. Magnitude could be the same so an object with a mag of 4 is brighter than one with a 3.
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22 Nov 2013   #73
Anak

Microsoft Community Contributor Award Recipient

Win 7 Home Premium 64bit Ver 6.1.7600 Build 7601 - SP1
 
 

You are not alone Gary, many people find it counter-intuitive that a high magnitude star is dimmer than a low magnitude star. Although both scales are logarithmic (star magnitudes and the decibel scale) we can attribute this counter-intuitiveness to the ancient Greeks, your argument would pale against two millennia of history and custom.

Quote:
Most ways of counting and measuring things work logically. When the thing you're measuring increases, the number gets bigger. When you gain weight, the scale doesn't tell you a smaller number of kilograms or pounds. But things are not so sensible in astronomy, at least not when it comes to the brightnesses of stars.

Star magnitudes do count backward, the result of an ancient fluke that seemed like a good idea at the time. Since then the history of the magnitude scale is, like so much else in astronomy, the history of increasing scientific precision being built on an ungainly historical foundation that was too deeply rooted for anyone to bulldoze it and start fresh.

The story begins around 129 B.C., when the Greek astronomer Hipparchus produced the first well-known star catalog. Hipparchus ranked his stars in a simple way. He called the brightest ones "of the first magnitude," simply meaning "the biggest." Stars not so bright he called "of the second magnitude," second biggest. The faintest stars he could see he called "of the sixth magnitude." This system was copied by Claudius Ptolemy in his own list of stars around A.D. 140. Sometimes Ptolemy added the words "greater" or "smaller" to distinguish between stars within a magnitude class. Ptolemy's works remained the basic astronomy texts for the next 1,400 years, so everyone used the system of first to sixth magnitudes. It worked just fine......

......Galileo forced the first change. On turning his newly made telescopes to the sky, Galileo discovered that stars existed that were fainter than Ptolemy's sixth magnitude. "Indeed, with the glass you will detect below stars of the sixth magnitude such a crowd of others that escape natural sight that it is hardly believable," he exulted in his 1610 tract, Sidereus Nuncius. "The largest of these...we may designate as of the seventh magnitude...." Thus did a new term enter the astronomical language, and the magnitude scale became open-ended. Now there could be no turning back. .......


.......The resulting magnitude scale is logarithmic, in neat agreement with the 1850s belief that all human senses are logarithmic in their response to stimuli. (The decibel scale for rating loudness was likewise made logarithmic.) Alas, it's not quite so, not for brightness, sound, or anything else. Our perceptions of the world follow power-law curves, not logarithmic ones. Thus a star of magnitude 3.0 does not in fact look exactly halfway in brightness between 2.0 and 4.0. It looks a little fainter than that. The star that looks halfway between 2.0 and 4.0 will be about magnitude 2.8. The wider the magnitude gap, the greater this discrepancy.

Source: Stellar Magnitude
Hipparchus only knew of one type of numbering system 1 to 9 and he gave the brightest stars the value of 1, any stars that diminished in his brightness scale were given an ascending number. There is some evidence he was aware of 0, but 0 wasn't used in his day as it is used now: Indo-Arabic numerals

With the advent of the telescope and its capability of seeing more and more stars the magnitude scale had to be expanded to include negative numbers.

If I understand the decibel scale correctly, 0db is the best quality signal. Anything above that is subject to distortion and anything below that represents a lower signal to noise ratio.
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22 Nov 2013   #74
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

Well using Hipparchus's logic it kind of makes sense, but people believed everything revolved around the Earth at one time.

Yeah the decibel scale is used for "loudness" and sound quality both.
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29 Nov 2013   #75
Anak

Microsoft Community Contributor Award Recipient

Win 7 Home Premium 64bit Ver 6.1.7600 Build 7601 - SP1
 
 

The jury is still out whether or not ISON survived it journey around the Sun. There are pictures that something survived, but:
  • Did the Sun corona blow out some of the coma and tail until it can rebuild?
  • Did the Suns' corona reduce the size of ISON?

Comet ISON down … but not out?



On another note:
Quote   Quote: Originally Posted by Britton30 View Post
Well using Hipparchus's logic it kind of makes sense, but people believed everything revolved around the Earth at one time.
At one time.
That period of time from the early 4th century to the middle of the 17th century was a huge dis-service to the human condition.

Ancient Libraries in the known world from Eastern Asia to the Middle East and around the Mediterranean
were well on their way in developing a storehouse of critical thinking.

The trouble started as usual because of religion and politics. The Roman Emperor Constantine I called The First Council of Nicaea in 325 a.d. and the human race suffered for the next 1,325 years until the Age of Enlightenment, and I fear that history is due to repeat itself because we as a people do not seem to learn from our past mistakes.






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29 Nov 2013   #76
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

It seems at least a good part of ISON made it through hell.

I noticed a very bright object in the early evening SW sky (6:48pm EST) a few days ago. It was about two out stretched arm hand widths up from the horizon. Two days later about 8;30pm EST I saw a similar object in the Eastern sky. This one was maybe 40-50 degrees up, I had not noticed either of them before.

The one in the SW sky was as bright as an aircraft landing light, the other slightly dimmer. The SW object turns out to be Venus, the other one Jupiter. I don't recall ever seeing them before.

Last night 28NOV about 10pmEST There was another oddity in the ESE sky, not nearly as bright but seemed to twinkle and flash with white, red, and blue colors, as if spinning fast.
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30 Nov 2013   #77
Anak

Microsoft Community Contributor Award Recipient

Win 7 Home Premium 64bit Ver 6.1.7600 Build 7601 - SP1
 
 

Quote:
I always find that writing the first line in a blog post is the hardest, and this has never been truer that now as I struggle to decide where I should even begin. My @SungrazerComets Twitter feed, and my email accounts, are all blowing up with questions about comet ISON. Many of them have already been answered, and many of them have unsatisfying answers, but I'll do my best. First, a little personal note...

Source: In ISON's Wake, a Trail of Questions | Comet ISON Observing Campaign
Determining Venus and then Jupiter was good sleuthing Gary!

If you noticed your oddity below the Constellation Orion and to the lower right of Jupiter, it would be Sirius which is also called the Dog star because it is in the Constellation Canis Major.
A Possible Naked-eye Comet in March, A Better One in December.-stel1.jpg

Why did it change colors?
Quote:
This is because of scintillation ("Twinkling") as the light passes through the atmosphere of the Earth. As the air moves in and out, the starlight is refracted, often different colors in different directions. Because of this "chromatic abberation," stars can appear to change colors when they are twinkling strongly.

Source: Curious About Astronomy: Why do stars change colour when they twinkle?


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30 Nov 2013   #78
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

Yessir, indeed it is Sirius, I'm serious. Strange how it seems to be the only "twinkle" at about the same height on the sky. It would seem other stars ,whole not as bright, would show some sort of twinkling passing light through the same atmospheric thickness.

EDIT: I checked Sirius much later in the night when it was near 45° elevation and the twinkling and colors were gone.
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01 Dec 2013   #79
Anak

Microsoft Community Contributor Award Recipient

Win 7 Home Premium 64bit Ver 6.1.7600 Build 7601 - SP1
 
 

Quote   Quote: Originally Posted by Britton30 View Post
Yessir, indeed it is Sirius, I'm serious. Strange how it seems to be the only "twinkle" at about the same height on the sky. It would seem other stars ,whole not as bright, would show some sort of twinkling passing light through the same atmospheric thickness.
Oh, but they do, but because of their lesser magnitude and greater distance from Earth it is harder to see.

It might be possible to see them twinkling in your 8power binoculars, but you would have to have them mounted on a tripod to keep them steady. A telescope would give you better results, 8power would be okay but a larger aperture/objective than 22mm, say 90mm would be better.

Quote   Quote: Originally Posted by Britton30 View Post
EDIT: I checked Sirius much later in the night when it was near 45° elevation and the twinkling and colors were gone.
There are several factors at play here; angle of incidence, extinction, and seeing.

Would you agree that the atmosphere is thinner as you go higher into it? It is this density difference that affects the twinkling.

I thought you would like to see this:
Quote:
A Possible Naked-eye Comet in March, A Better One in December.-sirius-twinkle.jpg

Twinkling is the rapid fluctuation in brightness and color of a star. It’s caused by slight changes in density of air pockets called “seeing cells” that move across the observer’s line of sight. Air’s refractive index is determined, in part, by its density. Such undulations cause slight, momentary defocusing of the starlight resulting in brightness changes, also called scintillation. In extreme cases, the star’s position hops around. Twinkling also produces rapid color changes because air is slightly dispersive, i.e. the index of refraction varies slightly with wavelength.

Both brightness and color twinkling are shown here in a five-second exposure of Sirius using a telephoto lens that was wiggled slightly during the exposure. As the star‘s twinkling image skated around the focal plane, it traced out graceful, colorful arcs, fading in some places, brightening in others.

Sources of both pic and quote: Sirius Twinkling - Earth Science Picture of the Day


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06 Dec 2013   #80
Anak

Microsoft Community Contributor Award Recipient

Win 7 Home Premium 64bit Ver 6.1.7600 Build 7601 - SP1
 
 
Turn Out the Lights, the Party's Over....

It was a good run, but all good things must come to an end....
Quote:
Dec. 4, 2013:
Astronomers have long known that some comets like it hot. Several of the greatest comets in history have flown close to the sun, puffing themselves up with solar heat, before they became naked-eye wonders in the night sky.

Some comets like it hot, but Comet ISON was not one of them.

Source: What Happened to Comet ISON?
In Memoriam | Comet ISON Observing Campaign


Thread is marked solved, but left open in case anyone has any astronomy questions, I'll be happy to try and answer.
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