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Counting the stars in the Pleiades

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#1 FoggyEyes

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Posted 27 September 2013 - 05:15 PM

LP where I live is terrible, but is clearly better in the morning. At around 6:00 I think that I can count five or six stars in the Pleiades with just my eyes (well, and glasses). Sound about right?

And, by the way, my eyes aren't very young and my vision prescription is about due to be updated.

#2 Tony Flanders

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Posted 28 September 2013 - 05:32 AM

LP where I live is terrible, but is clearly better in the morning. At around 6:00 I think that I can count five or six stars in the Pleiades with just my eyes (well, and glasses). Sound about right?


Yes, most people can see 5 or 6 stars in the Pleiades. It probably depends more on your eyesight than on the level of light pollution. Six Pleiads are brighter than magnitude 4.5, a typical limit for a very bright city sky.

#3 BrooksObs

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Posted 28 September 2013 - 05:41 AM

Yes, light pollution severely impacts what one sees in the way of stars in the Pleiades most places these days.

When I first move to my (then) rural home 40 years ago, on the best late autumn and winter nights I could count 14 stars in the group. Nowadays, with the light pollution situation growing ever worse by the year, I usually only manage 6.

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#4 SporQ

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Posted 28 September 2013 - 07:31 AM

You see six stars because the seventh sister is hiding. I believe that is how the myth goes.

#5 Seldom

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Posted 28 September 2013 - 09:56 AM

Wikipedia says Subaru (Japanese for Pleiades) means "unite". Is that the Japanese astronomical equivalent of "cluster?"

#6 rnc39560

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Posted 28 September 2013 - 01:58 PM

wow.... I don't really have BAD LP, and I only see a smudge of light with a couple bright dots! With my glasses!

#7 Seldom

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Posted 28 September 2013 - 02:05 PM

wow.... I don't really have BAD LP, and I only see a smudge of light with a couple bright dots! With my glasses!


Depends on how high they are. I looked at them last evening around 11:00 MDT, and they were a blur. When they culminate I can count 5 or 6. The OP was counting at 6:00 AM, just after culmination. Back in PA I saw the Pleiades from a clearing in tall trees. I was living in an orange zone, and could count at least 5 through my neighbor's security light glare. When I moved to UT, all I could see was a blur despite blue zone sky. Of course I was seeing them a lot closer to the horizon. Later in the year, when the Pleiades culminated before my bedtime I realized that the reason they looked so good in PA was that I could only see them when they were really high.

#8 Feidb

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Posted 28 September 2013 - 04:30 PM

It is known as the Seven Sisters, so seven is the magic number. However, the cluster is known to have over a thousand members so those seven are only the most recognizable members. Even in a large telescope, you'll never see anywhere near a thousand stars. Be happy with six or seven.

#9 mogur

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Posted 28 September 2013 - 06:28 PM

As I understand it the seventh sister was little Alcore. which deserted the group to pair up with Mizar. They remain together today. A cute story if nothing else!

BTW, I can see a couple dozen with a good 3 degree FoV.

#10 SteveNH

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Posted 28 September 2013 - 06:51 PM

Wikipedia says Subaru (Japanese for Pleiades) means "unite". Is that the Japanese astronomical equivalent of "cluster?"

In Japanese, the suffix "-dan" is the word used in astronomy to refer to a group or a gathering of stars; so in Japanese, the word for star cluster is "seidan" where "sei-" is the reading for the word "star" (pronounced like "SAY DONE").

#11 Kraus

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Posted 28 September 2013 - 10:24 PM

The seven daughters are right fun in the telescope. See how much nebulosity you can detect around the bright members. You might mistake it for fog on the eyepiece from your breath.

#12 Widespread

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Posted 28 September 2013 - 11:06 PM

Wikipedia says Subaru (Japanese for Pleiades) means "unite". Is that the Japanese astronomical equivalent of "cluster?"

In Japanese, the suffix "-dan" is the word used in astronomy to refer to a group or a gathering of stars; so in Japanese, the word for star cluster is "seidan" where "sei-" is the reading for the word "star" (pronounced like "SAY DONE").


The use of the term Subaru for the Pleiades apparently goes back to the mists of history (or the Nara Era, which is close enough).
It is thought to come from an (archaic) reading of a commonly used contemporary kanji which does indeed mean "to unite".

From what little I have seen, Japanese astronomical nomenclature seems likely to have been translated from other languages. Globs are kyujo seidan (Cue Joe, Say Don, lit. "Spherical star group"), OCs are sankai seidan (Son Kai, Say Don, lit. " Scattered open star group").

Best,
David

#13 Astrodj

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Posted 29 September 2013 - 12:07 AM

Yes, light pollution severely impacts what one sees in the way of stars in the Pleiades most places these days.

When I first move to my (then) rural home 40 years ago, on the best late autumn and winter nights I could count 14 stars in the group. Nowadays, with the light pollution situation growing ever worse by the year, I usually only manage 6.

BrooksObs


That beats me. The best I ever managed when my eyesight was still in it's prime from a good dark site was 12 for sure, 13 a definite maybe. And I had really good eyesight compared to most. I miss those days!

Now I'm down to six from my red zone backyard, but I can still get 7 from a yellow or green zone.

#14 Tony Flanders

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Posted 29 September 2013 - 08:58 AM

That beats me. The best I ever managed when my eyesight was still in it's prime from a good dark site was 12 for sure, 13 a definite maybe. And I had really good eyesight compared to most. I miss those days!

Now I'm down to six from my red zone backyard, but I can still get 7 from a yellow or green zone.


I doubt that most people could see more than 10 even in pristine skies.

The Pleiades are a particularly poor test for light pollution because they confuse two issues: seeing faint stars, and separating faint stars from the glow of much brighter stars nearby.

It's similar to seeing Jupiter's moons. All four Galilean moons are well above the limiting magnitude for a decent suburban sky, yet hardly anybody can see them naked-eye because they're obscured by the glare of Jupiter.

Likewise, the star 22 Tau is magnitude 6.4, which would normally be quite easy in a dark sky. But it's jut 2.5 arcminutes from much brighter 21 Tau. And both of those, in turn, are quite close to vastly brighter 19 and 20 Tau.

Given all those circumstances, it would indeed be a remarkable feat to see 22 Tau even in pristine skies. No doubt possible for a few people, but not for most.

The number of stars in the Pleiades also depends how far you're willing to go from the bright dipper formation. It's a very rich part of the sky, and in fact true cluster members of the Hyades are interspersed in the sky with true cluster members of the more distant Pleiades.

Incidentally, seeing 7 stars in the Pleaides is a bit exotic. I think people are more likely to see either 6 or 8, since the visibility of 16 Tau and 28 Tau (the 7th and 8th brightest stars) is quite similar.

#15 MikeBOKC

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Posted 29 September 2013 - 01:38 PM

The fascinating thing about M45 to me is not the number of stars I can see but the fact that this is a slowly dispersing cluster of recently formed stars that is one step along the continuum of stellar evolution exhibited by the Orion nebula. Most of the bright young stars in M45 are less that 100 million years old and they are slowly moving apart from their birth site, through some remaining interstellar gas. Plus when you look at M45 you can see what our own stellar neighborhood probably looked like about 4 billion years ago.

#16 Gert K A

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Posted 29 September 2013 - 05:28 PM

-Mike

The fascinating thing about M45 to me is not the number of stars I can see but the fact that this is a slowly dispersing cluster of recently formed stars that is one step along the continuum of stellar evolution exhibited by the Orion nebula. Most of the bright young stars in M45 are less that 100 million years old and they are slowly moving apart from their birth site, through some remaining interstellar gas. Plus when you look at M45 you can see what our own stellar neighborhood probably looked like about 4 billion years ago.


That... and also that they are very very pretty! :grin:

#17 Thorkill

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Posted 29 September 2013 - 05:57 PM

Tony interesting post. I see 6 at all times(With glasses) but the 7th and 8th keep showing emself if i work With side vision, but i dont see all 8 at once.

#18 rnc39560

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Posted 29 September 2013 - 06:41 PM

Ok! I went out EARLY morning, around 4:00 am. I could make out six. WITH my glasses...

#19 Lamb0

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Posted 29 September 2013 - 11:15 PM

I doubt that most people could see more than 10 even in pristine skies.

It's similar to seeing Jupiter's moons. All four Galilean moons are well above the limiting magnitude for a decent suburban sky, yet hardly anybody can see them naked-eye because they're obscured by the glare of Jupiter.

Incidentally, seeing 7 stars in the Pleiades is a bit exotic. I think people are more likely to see either 6 or 8, since the visibility of 16 Tau and 28 Tau (the 7th and 8th brightest stars) is quite similar.


You just need darker skies and younger eyes! :lol:

Twelve to fourteen Pleiades is NOT uncommon with younger (or very well preserved) eyes with adapted vision at a moderately dark site... YMWV :ubetcha:

All four Galilean moons are well above the limiting magnitude for a decent suburban sky as I consistently proved in college through my dorm room window (sans screen). Again, younger eyes are a boon although the separation should be near it's widest. Two are easy, the third is more difficult, but all four together are a visual challenge most youth and many adults (perhaps visually corrected) can achieve so long as they don't "know" it's impossible. :fingerscrossed:

Methodology (for verification) is part of it; but utilizing averted vision and other techniques takes practice (preferably learned from a mentor) for best results. Discriminating closely spaced point sources of light also requires practice under decent conditions. Start with Mizar & Alcor and other easy "doubles" when the Galilean satellites are not in view... it does get easier if your vision is up to it; and don't forget to challenge the younger set even if the gr'ups can't see them all unassisted. :watching:

#20 Tony Flanders

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Posted 30 September 2013 - 06:17 AM

Twelve to fourteen Pleiades is NOT uncommon with younger (or very well preserved) eyes with adapted vision at a moderately dark site... YMWV :ubetcha:


Do you have statistics to back that up?

All four Galilean moons are well above the limiting magnitude for a decent suburban sky


Of course they are -- as I said. But that doesn't mean that people can actually see them. The obstacle is Jupiter, not light pollution.

As I consistently proved in college through my dorm room window (sans screen). ... Two are easy, the third is more difficult, but all four together are a visual challenge most youth and many adults can achieve ...


Are you claiming to have seen all four Galilean moons simultaneously without optical aid? I have never heard anybody claim to do that before. It is certainly far beyond the ability of any normal person.

It is, of course, a matter of record that nobody described seeing any moons of Jupiter before the invention of the telescope.

#21 Thomas Karpf

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Posted 30 September 2013 - 06:46 AM

As I consistently proved in college through my dorm room window (sans screen). ... Two are easy, the third is more difficult, but all four together are a visual challenge most youth and many adults can achieve ...


Are you claiming to have seen all four Galilean moons simultaneously without optical aid? I have never heard anybody claim to do that before. It is certainly far beyond the ability of any normal person.

It is, of course, a matter of record that nobody described seeing any moons of Jupiter before the invention of the telescope.


Granted that no documents show that anybody has described seeing moons of Jupiter before Galileo, it's not entirely beyond the realm of possibility that someone with keen eyes saw them but didn't report it (after all, the Church might have considered it heresy, so why bring the subject up?). At maximum elongation (while at opposition), the moons are from 2.3 to 10.4 arc minutes from Jupiter, so there IS enough separation for it to be within the realm of possibility.

I can't speak to the glare issue from Jupiter, however.

#22 BrooksObs

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Posted 30 September 2013 - 07:59 AM


As I consistently proved in college through my dorm room window (sans screen). ... Two are easy, the third is more difficult, but all four together are a visual challenge most youth and many adults can achieve ...


Are you claiming to have seen all four Galilean moons simultaneously without optical aid? I have never heard anybody claim to do that before. It is certainly far beyond the ability of any normal person.

It is, of course, a matter of record that nobody described seeing any moons of Jupiter before the invention of the telescope.


Granted that no documents show that anybody has described seeing moons of Jupiter before Galileo, it's not entirely beyond the realm of possibility that someone with keen eyes saw them but didn't report it (after all, the Church might have considered it heresy, so why bring the subject up?). At maximum elongation (while at opposition), the moons are from 2.3 to 10.4 arc minutes from Jupiter, so there IS enough separation for it to be within the realm of possibility.

I can't speak to the glare issue from Jupiter, however.


Speculation and personal opinion about a situation is not evidence for it. It is fact that Venus could sometimes be perceived as nonstellar and even indications that some keen eyed observers could see that it displayed a crescent shape on occasion, is indeed evidenced in historical record. No one ever recorded seeing any faint attendants to Jupiter prior to the invention of the telescope as far as I can ascertain.

Likewise, even since the invention of the telescope, I have come across no accepted observations of ALL 4 Jovian satellites being seen simultaneously with the unaided eye by anyone reported in the literature. I regard a very significant percentage of extreme claims made by some observers, appearing since the rise of the internet, as leaning far more in the direction of imagination than reality.

BrooksObs

#23 Tora

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Posted 30 September 2013 - 08:06 AM

The "heresy" was that someone would suggest everything didn't revolve around the earth, not that Jupiter might have 4 'stars' close to it. I'm not seeing the conflict here...

Back on topic - I have always been able to see 6 or 8 which left me trying to figure out why it was the "seven-sisters" :lol:

#24 BrettG

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Posted 30 September 2013 - 08:38 AM

(wearing contacts) I see 6 from my backyard, naked eye. I have not been out with the binoculars or 'scope yet this year to get a count "aided". Still very nice. Hopefully as winter drags on, I will observe a few times.

#25 blb

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Posted 30 September 2013 - 08:52 AM

I need to really give the Pleiades a count once again. I have not really done this since my youth when I could count anywhere from 7 to 9 depending on the seeing. That always caused me to wonder why it was called the seven sisters but everything in the 60's said that seeing 7 was the norm for the average person. That's when I could see the milky way from in town, today on the best of nights I can see to mag. 4.5, but normaly to 4.2 is more typical.






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