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Observing >> Deep Sky Observing

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Starman1
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Reged: 06/24/03

Loc: Los Angeles
Re: Pleaides Nebulosity new [Re: Jeremy Perez]
      #5566386 - 12/11/12 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.


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blb
Post Laureate


Reged: 11/25/05

Loc: Piedmont NC
Re: Pleaides Nebulosity [Re: Jeremy Perez]
      #5566832 - 12/12/12 12:14 AM

Quote:

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.


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stmguy
sage


Reged: 10/11/12

Loc: Western NH
Re: Pleaides Nebulosity new [Re: blb]
      #5567269 - 12/12/12 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


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stmguy
sage


Reged: 10/11/12

Loc: Western NH
Re: Pleaides Nebulosity new [Re: stmguy]
      #5567361 - 12/12/12 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


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ensign
professor emeritus


Reged: 12/16/08

Loc: Southwestern Ontario
Re: Pleaides Nebulosity new [Re: Carol L]
      #5567585 - 12/12/12 01:29 PM

Quote:


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






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


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Daniel Mounsey
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Re: Pleaides Nebulosity new [Re: David Knisely]
      #5567902 - 12/12/12 04:22 PM

Quote:

Quote:

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.


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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Pleaides Nebulosity new [Re: Daniel Mounsey]
      #5567971 - 12/12/12 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.


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Pleaides Nebulosity new [Re: Daniel Mounsey]
      #5568000 - 12/12/12 05:36 PM

Quote:

Quote:

Quote:

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.


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kansas skies
sage


Reged: 12/02/12

Loc: Kansas, USA
Re: Pleaides Nebulosity new [Re: David Knisely]
      #5568257 - 12/12/12 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.

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Daniel Mounsey
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Re: Pleaides Nebulosity new [Re: David Knisely]
      #5568364 - 12/12/12 10:05 PM

David,

You raised some excellent point that deserve mention.


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Daniel Mounsey
Vendor (Woodland Hills)
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Reged: 06/12/02

Re: Pleaides Nebulosity new [Re: David Knisely]
      #5568473 - 12/12/12 11:35 PM

David,

I double checked the observational notes in NSOG on the nebulosity around M45 and they mentioned the use of an OIII with some subtle improvement. I find that rather odd. I'll do some tests this winter.


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Pleaides Nebulosity new [Re: Daniel Mounsey]
      #5568514 - 12/13/12 12:20 AM

Quote:

David,

I double checked the observational notes in NSOG on the nebulosity around M45 and they mentioned the use of an OIII with some subtle improvement. I find that rather odd. I'll do some tests this winter.




NSOG has a few misleading statements like that one (including one suggesting an OIII be used on the Horsehead, which is ridiculous). For filter use reports, I do not trust NSOG very much. While in sufficient aperture, the Merope portion might be visible in one of the broader OIII's, I would definitely not recommend one for use on that object. I saw a little improvement from my driveway on the Merope fan using the Orion Ultrablock narrow-band filter in my 10 inch Newtonian, but not much with a "true" OIII. However, the narrow-band view does not usually match the brightness seen in broad-band filters or without a filter under dark sky conditions. Clear skies to you.


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Sasa
professor emeritus


Reged: 11/03/10

Loc: Ricany, Czech Republic
Re: Pleaides Nebulosity new [Re: kansas skies]
      #5568700 - 12/13/12 05:55 AM

Quote:

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.




Yep, these are exactly the reasons why I tried to make the sketch. It forces you to make your mind and try to decide what is real and what to put down on the paper. At the end it sharpens the observer's ability to see, as you said. Also repeating the exercise is important. BTW, this was my second try, the first one (through 80mm scope) looked like: this. Unfortunately no more tries, there was no decent sky for DSO observing for last two months! There was always strong atmospheric haze which makes observing M45 nebulosity pretty much hopeless.

The negative concept is definitely not knew. But at that time, it was a "discovery" for me. Later on, I read for example, that O'Meara recommends similar approach for M45 in his book about Messier objects.


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Feidb
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Reged: 10/09/09

Loc: Nevada
Re: Pleaides Nebulosity new [Re: Sasa]
      #5568918 - 12/13/12 10:07 AM

As David points out, a true O-III doesn't help the nebulosity. When I tried both of mine, a 1 1/4" and 2" from different manufacturers over several decades, only one time did the one help just a tad on one night (I think it was the 1 1/4"). Most of the time, even that one blocked more than helped the nebulosity. The naked eyepiece worked better.

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Starman81
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Re: Pleaides Nebulosity new [Re: Feidb]
      #5569313 - 12/13/12 01:51 PM

I viewed M45 in the EON 80 with the XW 10 last night (50x, 1.4* TFOV) in my backyard (mag ~4.8 NELM that night) and I saw some haziness across the entire FOV. M45 was quite high in the sky as the time was past midnight. I turned the scope to the OC M41, which is much lower in the sky and did the view was clear with no haze at all. Did I see the nebulosity? I think so!

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northernontario
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Reged: 07/01/09

Loc: Porcupine, Ontario Canada
Re: Pleaides Nebulosity new [Re: Starman81]
      #5572591 - 12/15/12 01:14 PM

I have seen the striations of nebula a few times. Most nights it is visible with my 16 inch reflector. I seen the nebula faintly with my 6 inch refractor as well.

But the most outstanding view was with my 8" SCT on a cold, crisp transparent January sky a years ago.

Aperture is king, but sky conditions are equally important.

On another note...when all the stars you view look like there is nebula around them....it's time to go in...or get the blow dryer.

jake


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blb
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Reged: 11/25/05

Loc: Piedmont NC
Re: Pleaides Nebulosity new [Re: northernontario]
      #5572754 - 12/15/12 03:24 PM

Quote:

On another note...when all the stars you view look like there is nebula around them....it's time to go in...or get the blow dryer.




Even when there is no fog around any other star? I have been out many nights when there appeared to be no haze around any stars only to look at the Pleaides and see haze around the four or five brightest stars in it. I do not wont to go in then.


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northernontario
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Reged: 07/01/09

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Re: Pleaides Nebulosity new [Re: blb]
      #5572783 - 12/15/12 03:44 PM

Hi Buddy

I meant stars other than the ones in the Plaides.

I too, am very stuborn when seeing is good.

Even if it's a work night.

jake


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