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Pleaides Nebulosity

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#26 Starman1

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Posted 10 December 2012 - 06:55 PM

Carol,
That type of gas cloud is often referred to as "Galactic Cirrus".
Look at this deep photo of M81:
http://astrophoto.com/M81LRGBDEEP.htm
and look at how much "smoke" in the Milky Way overlaps the image of the galaxy.
When long exposures are made, it seems we see through that stuff in every direction we look.
Like this long exposure of Orion showing that all the nebulae in Orion are just bright points on one big nebula:
Orion
Or this one of M16/M17 showing they are connected:
M16/M17 I've see the bridge between them visually.

I wouldn't be surprised if a long enough exposure to the sky showed that such gas completely surrounds us. It's all a matter of how faint you go.

#27 Carol L

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Posted 10 December 2012 - 08:38 PM

Thanks for the links and info, Don... interesting stuff! :)

"... such gas completely surrounds us."
You mean something like this?

#28 MikeBOKC

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Posted 10 December 2012 - 09:37 PM

A vital and important study on the tinfoil hat issue:

http://berkeley.inte...arahimi/helmet/

I find this useful for UFO believers, bigfoot devotees and those awaiting the Mayan calendar doom moment.

#29 MikeRatcliff

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Posted 10 December 2012 - 10:25 PM

Or this one of M16/M17 showing they are connected:
M16/M17 I've see the bridge between them visually.


Wow, I had not heard of the bridge between M16/M17. And that it could be observed visually, double wow!

#30 Starman1

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Posted 11 December 2012 - 12:53 AM

Or this one of M16/M17 showing they are connected:
M16/M17 I've see the bridge between them visually.


Wow, I had not heard of the bridge between M16/M17. And that it could be observed visually, double wow!

With an O-III or UHC filter.
Don

#31 Sasa

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Posted 11 December 2012 - 07:24 AM

I had always a feeling when looking at M45 that there is something wrong with my optics (like the image is behind some very fine veil). It did not occur to me until last year that I'm seeing the nebulosity which is almost everywhere. A t that time I got an idea to invert the problem. Instead of tracing nebulosity (which is almost everywhere) I started to trace the dark areas. I saw many of them and I realize that I could see on good nights nebulosity in my 80mm and 100mm refractor even from my backyard. NGC1435 then became relatively easy one. But I could trace a lot of darker features (with some dificulties). I tried to record them on paper just to compare them later with the images and to have a feeling what I actually saw (I manage to do properly only the area south of the main stars, northen part is just a quick starting sketch, I run out of time). There are definitely many brighter areas which are not simply on the images (probably some groups of stars or just trick as one tends to put the bright patches around distinguished groups of stars). But some of the features seems to be real. This year I had no luck at all, the wether was quite bad so far...

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#32 Tony Flanders

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Posted 11 December 2012 - 07:48 AM

There are definitely many brighter areas which are not simply on the images (probably some groups of stars or just trick as one tends to put the bright patches around distinguished groups of stars). But some of the features seems to be real.


Looking at that sketch, it seems that the Merope Nebula is unquestionably real. The others look to me like classic connect-the-bright-dots pseudo-nebulosity. The same illusion that caused Messier to see nebulosity in M40 and M73.

#33 Sasa

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Posted 11 December 2012 - 08:15 AM

Yep, Tony, you are right. But except NGC1435, there seem to be at least one real stroke (coming from Electra), also the darker area between Merope and Electra seems to be real. The northern parts are just a quick impression drawing (as you were saying more or less connect-the-dots and atmospheric haze). My main point was that trying to trace the dark areas instead of the directly looking at nebulosity may lead to some success even from light polluted areas (my backyard is in small town just on the border of 1.5 million city).

#34 JIMZ7

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Posted 11 December 2012 - 09:19 AM

Back in the mid-1960's in the city limits of Detroit it was easy to see the misty nebula in Pleaides with a homemade 6" f/4 equatorial reflector made at Polaris Telescope Shop in Dearborn Michigan. Most of the scope/mount components came from Edmund Scientific. The eyepiece used was a 20mm Erfle. Life was simple back then and the skies were much darker in the "big city".

Jim :refractor:

#35 blb

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Posted 11 December 2012 - 01:44 PM

There are definitely many brighter areas which are not simply on the images (probably some groups of stars or just trick as one tends to put the bright patches around distinguished groups of stars). But some of the features seems to be real.


Looking at that sketch, it seems that the Merope Nebula is unquestionably real. The others look to me like classic connect-the-bright-dots pseudo-nebulosity. The same illusion that caused Messier to see nebulosity in M40 and M73.


Then please explain to me why it is on nights of good transparency/seeing that this connect-the-bright-dots pseudo-nebulosity does not appear around other bright star groups like the Hyades. When I can see it here where there is known nebulosity (with two NGC numbers) and nowhere else in that part of the sky can it be seen, is it really pseudo-nebulosity?
:question:

#36 Starman1

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Posted 11 December 2012 - 02:32 PM

IF you have no dew on any optical surface, and IF your optical surfaces are relatively clean, THEN seeing nebulosity around stars probably indicates there is nebulosity there.
In regard to The Pleiades, I almost always see patches of nebulosity around the stars and sections that extend well away from the stars.
I do not see that in the Perseus Double Cluster, or M35, or any other similarly-sized cluster of stars. They seem devoid of nebulosity.
There is visible nebulosity around the stars, surrounding the stars, and surrounding the cluster, that can be seen in relatively modest scopes.
What the aperture cutoff is can be determined by the altitude of the cluster, the experience of the observer, and all the same factors that influence the visibility of faint galaxies.

I find it ironic that the nebulosity is so easy in a 12.5" scope, but the view of the cluster is best in a scope like the TeleVue NP101, which doesn't show the nebula as well.

#37 StarStuff1

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Posted 11 December 2012 - 03:02 PM

Decades ago when skies were much darker I routinely saw nebulosity in M45. Nowadays it is much tougher. However, a few weeks ago I was viewing from a pretty light polluted area using a 70mm refractor working at f/2, an image intensifier eyepiece and an Orion Photographic SkyGlow filter. The nebulosity was definitely there!

#38 Tony Flanders

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Posted 11 December 2012 - 03:53 PM

Then please explain to me why it is on nights of good transparency/seeing that this connect-the-bright-dots pseudo-nebulosity does not appear around other bright star groups like the Hyades.


Because the Pleiades are brighter and tighter.

Mind you, I'm not saying that all the nebulosity is imaginary. But in this particular sketch, there's a mighty lot of it falling along nearly straight lines between bright nearby stars in places where photos show little or no nebulosity.

#39 markgliderpilot

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Posted 11 December 2012 - 04:17 PM

I was looking at the Pleiades only last night. Using APM binos with 19mm panoptics fitted with dew heaters II swung across to the magnificent Pleiades star cluster, M45. This is always a stunning sight in the binoculars, a veritable field of brilliant diamonds with chains of fainter stars radiating in all directions.  There is also some faint nebulosity within the Pleiades, the left over dust and gas from when this cluster was born.  I am always sceptical when I can see the faint glow around the brighter stars from a light polluted site such as my small town observatory.  While it could be the nebulosity, it is more likely to be a faint fogging of the optics or the glow from any atmospheric humidity lit up by the streetlights.  Although it was a very transparent night, there was clearly some mist about so the heaters were on keeping the optics free from dew. 
 
It was with these thoughts in mind that I studied the glow around the brighter stars.  After a few minutes I noticed very dark “ink spots” between the stars.  It was with a thrill that I realised that I was indeed picking out the faint nebulosity and noticing its contrast with the black background sky.  I will now have to make a detailed sketch of this wonderful cluster including the nebulosity from home and our dark sky site.

Best regards

Mark

#40 Jeremy Perez

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Posted 11 December 2012 - 04:40 PM

I spent a couple evenings over the weekend observing and sketching the Pleiades naked eye and through 15 x 70 binoculars. The Merope nebula was the only one I could confidently detect with binoculars--its brightness and asymmetry really seem to do the trick for visibility. Overall though, I'm cautious about the appearance of nebulosity that seems to engulf the cluster. It definitely appears that way! However, I just don't think my equipment and my eyes are up to the task of sorting glare from nebulosity at those scales.

To pull on what Tony said, in my personal experience, the combination of magnitude and tight grouping in the Pleiades doesn't compare well to other clusters (such as the Hyades and Double Cluster). So I don't feel I can rely on those as a baseline. The combined, overlapping glare of all those bright stars so close to one another just seems to have a unique, overpowering effect. With that said, if I were to make some decisive upgrades to my choice of binoculars, perhaps I could cross a glare threshold there. As for naked eye, my overcorrected stargazing glasses are as good as it gets, and I can't convince myself that the amazing, hazy glow isn't simply combined glare from the bright members and perhaps integrated light from the other fainter, embedded and surrounding stars.

I still need to go back and do a closer telescopic study and see what I can pull out at higher magnifications!

#41 Starman1

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Posted 11 December 2012 - 06:08 PM

As an aside, I read the nebulosity associated with the Pleiades was not the nebula in which the stars were born, but merely a cloud of gass the stars were passing through.
I presume they figured that out by measuring the differential in motion between the stars and the nebula.

#42 blb

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Posted 12 December 2012 - 12:14 AM

To pull on what Tony said, in my personal experience, the combination of magnitude and tight grouping in the Pleiades doesn't compare well to other clusters (such as the Hyades and Double Cluster). So I don't feel I can rely on those as a baseline. The combined, overlapping glare of all those bright stars so close to one another just seems to have a unique, overpowering effect...


I would agree with you if I were using binoculars too, but I am using a 4-inch TV-102 refractor. It also would seem to me that if this were a true pseudo-nebulosity, then every time I looked at the Pleaides you could see it, but this isn't the case at all. In fact, like I said, it is only on nights of good transparency/seeing that this nebulosity is visible. That alone argues against it being any pseudo-nebulosity.

#43 stmguy

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Posted 12 December 2012 - 10:11 AM

After what seems like a long spell of cloudy weather it actually looks like it might be clear tonight and tomorrow. I may actually get a chance to check for the nebulosity around the Pleiades !
Norm

#44 stmguy

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Posted 12 December 2012 - 11:16 AM

Sometimes we get caught up in the science and forget the beauty.

Thought I would share a couple of quotes:

The poet Lord Tennyson mentions the Pleiades in his poem Locksley Hall:

"Many a night I saw the Pleiads, rising through the mellow shade,
Glitter like a swarm of fire-flies tangled in a silver braid."

And:

Job 38:31 KJV
Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion?

Norm

#45 ensign

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Posted 12 December 2012 - 01:29 PM

. . . I hope none of the tinfoil-hat gang reads this . . .


:roflmao:

"tinfoil-hat gang" sounds like a great name for a band or for something in a Mel Brooks Western.

#46 Daniel Mounsey

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Posted 12 December 2012 - 04:22 PM

Can the nebulosity associated with the Pleaides be observed visually or is it only visible via AP? If it can be visually observed is the a particular filter that may help? I observe mostly under light polluted skies so I don't see it from here but I'd like to try from a real dark site.

Thanx, Dave

Dave


The nebulosity requires a good sky, but is slightly enhanced by the use of a broad-band LPR filter (Lumicon Deep-sky, Orion Skyglow, etc.). I find that with my 100mm f/6 refractor from my driveway in-town, I can't see the nebulosity in the Pleiades very often, but using my Orion Skyglow filter, it starts to become visible on most any good dark night from my home, although it is still pretty faint (requires averted vision). Outside of town at my dark sky site (ZLM 6.5), a filter isn't usually needed. Indeed, even in my 80mm f/5 refractor at low power, the nebulosity isn't all that difficult. The part that usually shows up more prominently is the area around and south of the star Merope, where a faint broad fan of diffuse light can sometimes be seen extending away from that star. The other areas of nebulosity are much harder to detect visually, although they can be imaged fairly easily in long time exposures of the cluster. In my 14 inch, I can sometimes see hints of a wispy structure to the nebula, but overall, it is more of just a diffuse glow of slightly varying brightness than anything else. Clear skies to you.


David,

I find it very interesting that you've used a broadband filter on M45 since the OP inquired about the use of a filter in the first place. It isn't often that we associate nebula filters while observaing reflection nebulas but I think you raised a very interesting point that deserves more observational attention. I'm just thinking out loud here but the bandpass on the broadband falls between 442nm to 532nm while IC353 falls in at 450nm. Interestingly I've never even bothered to play with a broadband on IC353 even though I have seen it on numerous occasions on crystal clear nights without any such filters. Even if the results using a broadband are extremely subtle, I think it's worth a look. I'm not sure if you mentioned this in your deepsky/nebula review yet.

#47 GlennLeDrew

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Posted 12 December 2012 - 05:09 PM

It's too bad some other similar in size/brightness but 'nebula-less' cluster weren't located nearby for more relevant comparison. The Hyades is just too different, it seems to me.

It occurs to me that an interesting experiment to try--if one were sufficiently driven--is to make up a multi-element occulter. In effect, this would be an enlarged map of the principal Pleiads, the stars being opaque disks held together by a minimalist wire framework. The size would be such that it would subtend the correct angular extent when placed sufficiently distant so that both eyes could be used simultaneously. So as to not require excessive distance for placement, the star blocking disks should be made as large as practicable, but without masking too much of the immediately surrounding and brightest nebulosity.

Such a construct would eliminate much of the scatter in the optics and (more significantly) the eye, which tend to confuse things.

Alternatively, a mask of dots placed on a filter would help to eliminate eye-induced scatter, although only some instrumental scatter.

The first clue, as far as I understand, that the cluster and nebulosity were not related came from visual inspection of IRAS images, where it was clear that the stars were sweeping a wake through the surrounding dust. It may be the case that this was in agreement with the then known proper motion of the cluster members across the sky.

#48 David Knisely

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Posted 12 December 2012 - 05:36 PM

Can the nebulosity associated with the Pleaides be observed visually or is it only visible via AP? If it can be visually observed is the a particular filter that may help? I observe mostly under light polluted skies so I don't see it from here but I'd like to try from a real dark site.

Thanx, Dave

Dave


The nebulosity requires a good sky, but is slightly enhanced by the use of a broad-band LPR filter (Lumicon Deep-sky, Orion Skyglow, etc.). I find that with my 100mm f/6 refractor from my driveway in-town, I can't see the nebulosity in the Pleiades very often, but using my Orion Skyglow filter, it starts to become visible on most any good dark night from my home, although it is still pretty faint (requires averted vision). Outside of town at my dark sky site (ZLM 6.5), a filter isn't usually needed. Indeed, even in my 80mm f/5 refractor at low power, the nebulosity isn't all that difficult. The part that usually shows up more prominently is the area around and south of the star Merope, where a faint broad fan of diffuse light can sometimes be seen extending away from that star. The other areas of nebulosity are much harder to detect visually, although they can be imaged fairly easily in long time exposures of the cluster. In my 14 inch, I can sometimes see hints of a wispy structure to the nebula, but overall, it is more of just a diffuse glow of slightly varying brightness than anything else. Clear skies to you.


David,

I find it very interesting that you've used a broadband filter on M45 since the OP inquired about the use of a filter in the first place. It isn't often that we associate nebula filters while observaing reflection nebulas but I think you raised a very interesting point that deserves more observational attention. I'm just thinking out loud here but the bandpass on the broadband falls between 442nm to 532nm while IC353 falls in at 450nm. Interestingly I've never even bothered to play with a broadband on IC353 even though I have seen it on numerous occasions on crystal clear nights without any such filters. Even if the results using a broadband are extremely subtle, I think it's worth a look. I'm not sure if you mentioned this in your deepsky/nebula review yet.


I had a couple of objects that turned out to be primarily reflection nebulosity that I included in my survey, but generally, I tried to stay away from them, as they are not generally helped very much by the use of narrow-band and line filters. There are a number of reflection nebulae that are helped to some mild degree by the broad-bands, such as the reflection component of M20 or the "Iris" Nebula (NGC 7023). Indeed, under the pristine dark skies of the Nebraska Star Party, in my 14 inch Newtonian, the view of the entire M20 complex was best in my Orion Skyglow filter than in any other filter (and better than the view without a filter even at that dark location). People forget that even at a dark sky site, there are the atmospheric Sodium D lines and the atomic Oxygen lines that can be partially or totally excluded by a good broad-band LPR filter. Clear skies to you.

#49 kansas skies

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Posted 12 December 2012 - 08:51 PM

From my yellow zone observing location, I pretty much always see nebulosity around the Pleiades. My impression is more that of high level atmospheric haze than fogged optics (which tend to uniformly cover and fog the entire field of view). Sometimes when I will check other bright stars in the area, I find nebulosity (or haze) around them and sometimes I don't. This threw me for awhile until I finally decided that on really clear days, I had to be seeing the nebulosity and on those days of lesser transparency, I was probably just seeing the haze or possibly a combination of the two. I also would like to say that I found Sasa's drawing to be quite good. Although drawing negative space is not a new concept, it seems to have been applied very well to this drawing. As for seeing details that aren't really there, that is to be expected when one is trying to stretch the limits of seeing beyond that which is readily apparent. My guess is that if this exercise were repeated over a number of observing sessions, the details would eventually take care of themselves. If nothing else, it appears to be a very effective way to enhance one's ability to see.

#50 Daniel Mounsey

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Posted 12 December 2012 - 10:05 PM

David,

You raised some excellent point that deserve mention.






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