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General Astronomy >> General Observing and Astronomy

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2orthern2ights
journeyman


Reged: 10/13/13

M57 central star?
      #6135131 - 10/13/13 02:21 PM

Does anyone have a picture that points out the central star in the ring. I've read alot about people seeing it on the web but no where can I find directions on how to locate it. The general concensus on the star that is brighter in the center of the ring is that; that is not the star, but a star closer to us in a chance alignment to appear as if it was the central star. Where could the real central star be?

I have read all the pages about amature observations and seeing requirements, etc, etc,. But, at the moment, I can't find it because I have no idea where it is... Quite honestly I'm not gonna hold my breath. It is soo close to the limiting magnitude of my 14" that I doubt I would notice it. Never mind that it is set against a glowing nebula. But a photo should show it. Is it not in this photo?

http://imgsrc.hubblesite.org/hu/db/images/hs-2013-13-a-print.jpg

Im assuming that the central star, for the majority of people that peer through a telescope eyepiece, is the bright star in the center of the ring. This summer an amature astronomer, at my 14" telescope, said he witnessed the central star. To his defence, it appears dead center of the ring, it's pretty dim, nowhere can you find somthing to say otherwise... I guess I have seen it too. *reaches for belt notching tool*

Edited by 2orthern2ights (10/13/13 02:22 PM)


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SUN RA KAT
super member


Reged: 09/10/11

Loc: Centerville, Ohio USA
Re: M57 central star? new [Re: 2orthern2ights]
      #6135261 - 10/13/13 03:34 PM Attachment (58 downloads)

20 second exposure a few nights ago with my C14 with a Lumicon Giant EZ Guider with reducer lens and Nikon D800 @ ISO 1600. System should be around F7. Unguided.

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brentwood
Carpal Tunnel
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Reged: 11/04/05

Loc: BC Canada
Re: M57 central star? new [Re: SUN RA KAT]
      #6135309 - 10/13/13 04:04 PM

If it makes you feel better, I have looked at the Ring with a 72" (yes really) for 10-15 secs, and could NOT see the central star!

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northernontario
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Reged: 07/01/09

Loc: Porcupine, Ontario Canada
Re: M57 central star? new [Re: brentwood]
      #6135315 - 10/13/13 04:07 PM

I too, with my 16 inch from a reasonably dark yard, have never seen it either.

But

The rest of sure does look nice.

Were you able to see any color with the 72 inch Brentwood?

jake


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brianb11213
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Reged: 02/25/09

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Re: M57 central star? new [Re: brentwood]
      #6135402 - 10/13/13 05:00 PM

Quote:

If it makes you feel better, I have looked at the Ring with a 72" (yes really) for 10-15 secs, and could NOT see the central star!



To see really faint objects requires (a) a MINIMUM of AT LEAST ONE HOUR's dark adaptation in a completely dark environment, (b) experience of how to use averted vision effectively, (c) object near the zenith in a dark, transparent sky, (d) a magnification of about 20x per inch of aperture to dilute the sky background and (e) seeing sufficiently steady to support that magnification.

Given most of that I've been able to see stars down to mag. 16.2 with my 11" SCT - but if I looked for 10 sec only I don't think I'd get within a magnitude of that. It takes ~10 minutes observing to get sufficient intermittent glimpses with averted vision to spot an object at the limit of vision.

So the central star of M57 catalogued at mag. 14.7 should be an easy object for me, right? No, it isn't. The "bright" background of the nebula makes it very difficult indeed ... perhaps more magnification might help ... I find the mag. 13 star just outside the ring to be really easy with 11" and can see it fairly easily with 4.3". My suspicion is that the magnitude of the central star is catalogued incorrectly.


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azure1961p
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Reged: 01/17/09

Loc: USA
Re: M57 central star? new [Re: brianb11213]
      #6135622 - 10/13/13 06:53 PM

I agree with Brian though a lot of folks who've found success tend to seem to go around 40x per inch. I'm not in that camp Ive still not seen it. I will say too, 10-15 seconds isn't nearly long enough for a threshold magnitude. On the faintest things Ive blown a whole half hour to confirm a sighting. If I had the ten second rule - I'd probably lose a full magnitude off my best effort.

By the way the central star - is - well - in the center. Really.
Pete

Edited by azure1961p (10/13/13 06:56 PM)


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pstarr
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Reged: 09/17/04

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Re: M57 central star? new [Re: 2orthern2ights]
      #6135631 - 10/13/13 06:58 PM Attachment (40 downloads)

Here is a magnitude chart of surrounding stars. If you can't see some of these, you won't see the center star.

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brentwood
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Reged: 11/04/05

Loc: BC Canada
Re: M57 central star? new [Re: pstarr]
      #6135688 - 10/13/13 07:32 PM

When I looked through the 72" (DAO, Victoria BC) I was dark adapted as much as I would have been at home. I am also familiar with using averted vision. I think it as others have said, 10-15 seconds is simply not enough time. When you are in a long line of people, most of whom look for 2-3 seconds, and say, "That's nice", that was about as long as I dared!
BTW, as I would never ask "What magnification is this", the Ring itself was about as big as an oval made with your fingers in front of your face!


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jgraham
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Reged: 12/02/04

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Re: M57 central star? new [Re: brentwood]
      #6135696 - 10/13/13 07:38 PM

There was a long discussion of this in the deep sky observing forum. My take-away was that this is not easy. I have tried many times to glimpse the central star with my 16" and 16.5" scopes and at best I can say possibly maybe, but not for sure. Interestingly, my impression is that it is the nebula obscuring the star that makes it tough. If nothing else, it is a fun challenge.

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azure1961p
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Re: M57 central star? new [Re: jgraham]
      #6135722 - 10/13/13 07:52 PM

Folks who've seen it weigh big on the need to have great seeing - no doubt the reason the 72" didn't budge. Had the diffraction pattern been defined itd been easy as pie. But such is the smearing effect .

Pete


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kfiscus
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Reged: 07/09/12

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Re: M57 central star? new [Re: azure1961p]
      #6135808 - 10/13/13 08:46 PM

My observing buddy and I have seen it several times with our Z12s. The seeing has to be very good and you have to use very high magnifications. We never try unless Lyra is near the meridian. This is made much easier with an EQ platform.

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Feidb
Carpal Tunnel


Reged: 10/09/09

Loc: Nevada
Re: M57 central star? new [Re: kfiscus]
      #6135928 - 10/13/13 10:02 PM

The central star is an extreme challenge for most nights and apertures. The problem is not only the very dim magnitude (15.7), but the lack of contrast against the brightness of the nebula.

I've seen it twice, once with my home-built 16-inch f/6.4 in the mid-90's and once with my 16-inch f/4.5 commercial scope a few years ago. The conditions were pristine and I caught it just right. It took 300+ magnification both tries. The transparency and seeing were superb.

The thing is that there are some people with super eyes and perfect conditions (both optical and weather) that have caught it in as small as 8-inch scopes, or so I've heard. Yet as one of you pointed out, it can be invisible in a 72-inch.

Dimness and contrast against the nebula. Tough to almost holy grail. The visual mag. of 15.7 which is theoretically beyond the reach of an 8-inch scope? I can't say. I've heard of someone with a 12-inch that sees it quite often.


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2orthern2ights
journeyman


Reged: 10/13/13

Re: M57 central star? new [Re: Feidb]
      #6136184 - 10/14/13 01:17 AM

ok... thanks a lot to everyone for weighing in on this one. We still got a problem. No map to the whereabouts of this terrestrial sized 15th magnitude white dwarf that shines in uv and blue. Tomorrow when I get back home I'll look into this. If you got time to look into this that'd be awsome. There are still mysteries in one of the most popular objects on anyones list! Amazing!

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Illinois
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Reged: 12/18/06

Loc: near Dixon, Illinois USA
Re: M57 central star? new [Re: 2orthern2ights]
      #6136424 - 10/14/13 08:35 AM

I looked at M57 many times on my 16 inch dobsonian and I never see a central star. Maybe very crystal clear and very dark sky at high power!

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Achernar
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Reged: 02/25/06

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Re: M57 central star? new [Re: 2orthern2ights]
      #6137114 - 10/14/13 02:00 PM

I have never seen it, even through my 15-inch because the seeing in general is just not good enough for that. A faint star embedded in nebulosity is a tough nut to crack, I have noted how poor seeing hides the central stars of the planetary nebulae NGC-7662, NGC-6543 and NGC-7009 whereas during good seeing I can see them without too much trouble with my 10-inch. I have tried magnifications as high as 572X on the Ring Nebula without success looking for its central star.

Taras


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payner
scholastic sledgehammer
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Reged: 03/22/07

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Re: M57 central star? new [Re: Achernar]
      #6137217 - 10/14/13 02:48 PM

I have seen the central star through my C-14 (has since gone to a new home ). Seeing was excellent on those times of viewing it, near a 5/5. Unforgettable once you see it.
Best,
Randy


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hbanich
Pooh-Bah
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Reged: 06/17/05

Loc: Portland, Oregon
Re: M57 central star? new [Re: 2orthern2ights]
      #6137333 - 10/14/13 03:58 PM Attachment (11 downloads)

Quote:

ok... thanks a lot to everyone for weighing in on this one. We still got a problem. No map to the whereabouts of this terrestrial sized 15th magnitude white dwarf that shines in uv and blue. Tomorrow when I get back home I'll look into this. If you got time to look into this that'd be awsome. There are still mysteries in one of the most popular objects on anyones list! Amazing!




The central star really is the one in the middle -


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dpwoos
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Reged: 10/18/06

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Re: M57 central star? new [Re: hbanich]
      #6137921 - 10/14/13 09:46 PM

I am skeptical of most claims. The only reported observation that I 100% accept is by my older son, who observed it in a 60" scope on Mt. Lemmon. He says that it was not super easy to see. Of course, my skepticism doesn't make other claimed sightings false, and everybody decides for themselves who and what to accept, and with what degree of certainty. I do know that it is very easy to see what you want to see, especially if you know the exact location of the target.

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kfiscus
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Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: M57 central star? new [Re: dpwoos]
      #6138016 - 10/14/13 10:47 PM

To twist your words (but hopefully not your tail) I wanted to see it and it wasn't easy. It took the convergence of very good seeing, a collimated and cooled 12", smooth tracking, and high magnification. The star would show itself for 1/2 a second or so. The central star was easier while out at the Nebraska Star Party and its DARK skies.

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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: M57 central star? new [Re: brianb11213]
      #6138269 - 10/15/13 02:23 AM

brianb11213 wrote:

Quote:

So the central star of M57 catalogued at mag. 14.7 should be an easy object for me, right? No, it isn't. The "bright" background of the nebula makes it very difficult indeed ... perhaps more magnification might help ... I find the mag. 13 star just outside the ring to be really easy with 11" and can see it fairly easily with 4.3". My suspicion is that the magnitude of the central star is catalogued incorrectly.




According to Brian Skiff of Lowell Observatory, with professional photometry of the central star, all published photometric measurements report the central star's visual magnitude at about 15.0 or perhaps one to three tenths fainter, and with no demonstrated evidence of variability. The smallest telescope I have managed to see the central star in is a 9.25 inch SCT (480x), which was also just barely showing stars down to 15.3 in the area around M57. This would tend to support the figure of magnitude 15 for the central star. Clear skies to you.


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: M57 central star? new [Re: dpwoos]
      #6138285 - 10/15/13 03:00 AM

Quote:

I am skeptical of most claims. The only reported observation that I 100% accept is by my older son, who observed it in a 60" scope on Mt. Lemmon. He says that it was not super easy to see. Of course, my skepticism doesn't make other claimed sightings false, and everybody decides for themselves who and what to accept, and with what degree of certainty. I do know that it is very easy to see what you want to see, especially if you know the exact location of the target.




I can understand your skepticism, but I no longer have nearly as much with reports of this elusive object. There is indeed something of an "illusion" caused by the glowing interior of M57 that, at lower powers, can make one seem to see a faint star-like point in the middle of the ring that may not really be there. I recall my first view of M57 in Behlen Observatory's 30 inch Classical Cassegrain (Univ. of Nebraska, Lincoln) at a public night around 1975, and the central star was nowhere to be seen. I asked my professor Dr. Don Taylor about it at the time. He said that he had never seen the star even in Steward Observatory's 90 inch at Kitt Peak, so I flatly passed it off as impossible in amateur telescope. Indeed, at our local star parties, it became something of a joke among us when sighting claims for the star popped-up.

However, a number of years later, I learned just how wrong I was. We were at one of our club's regular star parties south of Lincoln under dark skies when one of our members called out to me to have a look at M57's central star in his 20 inch Obsession. I said to myself, "Yea, right", but then went over to the 20 inch scope and took a look in. At something over 400x, right dead-center in the middle of the ring, THERE WAS THE CENTRAL STAR!! It was OBVIOUS and visible with DIRECT vision. Then, something incredible happened: IT ABRUPTLY VANISHED! It almost seemed to have turned-off as quickly as if someone had turned it off with a light switch. Then, as quickly as it had vanished, it abruptly reappeared right where it had been before. As I watched, it gradually faded, quickly brightened, and then quickly faded out completely, and by that time, I knew exactly what was happening. The seeing was blurring the star's tiny diffraction disk, causing it to enlarge and eventually completely blend-in to the glowing nebular background in the interior of the ring. At times, it would almost blink on and off, while at other times, it wasn't visible at all no matter how hard I tried.

To see the central star, one has to watch the nebula at rather high magnification (well over 300x) to reduce the apparent surface brightness of the interior of the ring, while at the same time, watching for an extended period of time to catch moments of really good stable seeing. Once I understood this, I went back to my 10 inch Newtonian, cranked up the power to around 440x and waited. Sure enough, every once in a while, the faint central star would "pop" on and off as if some giant alien was playing with its power switch. It was quite faint (around 15.0) but it was there. Some nights, the seeing never gets good enough to see the central star at all no matter how big the telescope is, so it is no wonder that some with very large scopes often never see it. While a larger aperture helps, I have seen the central star (barely) in a 9.25 inch aperture SCT (from my magnitude 5.6 driveway no less), so it *is* at least possible in moderate amateur telescopes. A couple of weeks ago, I had it in my 14 inch and it was only visible for a few seconds at a time before it vanished once again, often for a number of minutes.

Again, the keys to viewing M57's central star are:

1. modestly dark skies (and good dark adaptation).
2. apertures larger than eight inches.
3. very high power (well over 300x).
4. very stable seeing.
5. watch for an extended period of time.


It is OK to be somewhat skeptical sometimes, but in this case, the truth of the matter is, the central star of M57 can indeed be seen in amateur telescopes. Clear skies to you.


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: M57 central star? new [Re: pstarr]
      #6138290 - 10/15/13 03:05 AM

Quote:

Here is a magnitude chart of surrounding stars. If you can't see some of these, you won't see the center star.




Uh, that's MY chart BTW.... (prepared from a DSS image I processed with photometry provided by Brian Skiff of Lowell plus other sources).


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brianb11213
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Reged: 02/25/09

Loc: 55.215N 6.554W
Re: M57 central star? new [Re: David Knisely]
      #6138328 - 10/15/13 04:10 AM

Excellent post, David!

Quote:

Again, the keys to viewing M57's central star are:

1. modestly dark skies (and good dark adaptation).
2. apertures larger than eight inches.
3. very high power (well over 300x).
4. very stable seeing.
5. watch for an extended period of time.





Points 1, 2 & 4: no dispute.
Point 3: I'm skeptical of the need for more than 20x per inch of aperture. It's at about this point that the diffraction disc of a point object (star) starts to become extended and there is no further gain in contrast between star & background by going higher. Smearing out the star tends to reduce its visibility in the same way that poor seeing does.

5. I'm glad you mentioned this. I've long since learned that it takes 10 - 15 minutes concentrated effort to be sure of the visibility or otherwise of objects very close to the limit. When seen, they're always seen as glimpses only, even with skilled use of averted vision. (This is also the case when the seeing is "perfectly steady" as is sometimes the case when observing with small scopes.) I think it is because it takes several photons arriving at the same site within a short period of time (~0.1 sec) to generate a signal which the brain can interpret as a glimpsed star. As the star brightness decreases, the average arrival time between the photons increases to the point where the star is not seen steadily ... but the photon arrival is a Poisson process, so that there are occasions when enough photons arrive in a burst to allow an instantaneous glimpse.

At this level a single glimpse isn't enough, you have to look carefully to allow several glimpses all from the same point to be registered before you can be "sure" that the object is seen.

At the limit (i.e. for me to see a mag. 16.2 star at the zenith in good sky conditions with my 11" SCT) this process takes 10-15 minutes.

Quote:

It is OK to be somewhat skeptical sometimes, but in this case, the truth of the matter is, the central star of M57 can indeed be seen in amateur telescopes.



Indeed. I have seen it with my 11" SCT. But it's an extremely difficult object, in the way that a "normal" mag. 15 star shouldn't be.


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Achernar
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Reged: 02/25/06

Loc: Mobile, Alabama, USA
Re: M57 central star? new [Re: David Knisely]
      #6138601 - 10/15/13 09:14 AM

Interesting how it popped into and out of view, I will try watching M-57 for an extended period to see if it becomes visible that way.

Taras


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JimMo
I'd Rather Do It Myself


Reged: 01/08/07

Loc: Under the SE Michigan lightdom...
Re: M57 central star? new [Re: Achernar]
      #6138984 - 10/15/13 12:47 PM

Quote:

I will try watching M-57 for an extended period to see if it becomes visible that way.

Taras




I've done this many times when it is tracking near the zenith and I've only seen it once in my 14.5" dob under high mag and great seeing from a green zone. It did pop into and out of view and patience was needed because it was mostly out.


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Dwight J
scholastic sledgehammer
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Reged: 05/14/09

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Re: M57 central star? new [Re: David Knisely]
      #6139048 - 10/15/13 01:18 PM

Having the central star vanish is exactly what has happened the 3 X I have seen it (2X in a 13.1" & 1X in a 16"). About 20 seconds after seeing it the star winked out of our vision. Waiting 30 seconds to a minute and looking again had it reappear. Since it is a very tiny spark perhaps while concentrating on it I did not breath or did so in a shallow manner and the O2 level in my blood dropped. Stepping away recharged my oxygen level and I was able to see it again. My observing buddy had the same experience. I know that I did spot it as when I saw it I stepped away from the scope so my buddy could have a look and he exclaimed "I see the central star!" This happened on two of the three occasions. Seeing may br a function of the atmospheric seeing as it is very very small. It was also directly overhead and we were at dark sky sites ranging from 3000 - 4400 ft elevation. Seeing the central star is certainly a rare event as I must have looked at M57 over a thousand times. Some say the star is variable in brightness and this may play a role in it's visibility.

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Bill Weir
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Re: M57 central star? new [Re: brentwood]
      #6139135 - 10/15/13 01:58 PM

Quote:

If it makes you feel better, I have looked at the Ring with a 72" (yes really) for 10-15 secs, and could NOT see the central star!




So how long ago was that? There hasn't been an eyepiece on the Plaskett in decades.

I'm not surprised you didn't see the CS because almost more than anything seeing the CS of M57 depends on seeing. Despite the often good seeing experienced on Observatory Hill if you were looking though that scope on a Saturday evening public night with many people in the dome there was probably an amazing heat plume rising through the slit. The pinpoint of the white dwarf can't be spead out due to poor seeing or it becomes diffused into the background brightness. This is why patience and tracking help so much in catching these fleeting glimpses. I also wonder as to the quality of the figure and roughness of surface to that almost 100 yr old mirror. I've imaged with it and seen the images done by others. The stars alway have a fair deal of bloat to them.

Actually fairly regularly I will see the CS in M57 with my 20" if I take the time to observe it and then it will flicker in and out. Even with my 12.5" I've seen it on more than a few occasions with the often good seeing experience here at the southern tip of the island and from the top of Mt Kobau. I consider looking for the CS in M57 similar to planetary observing. You are waiting for those moments within the regular seeing where the pockets of good seeing pass by and the detail shows through.

Bill


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David Knisely
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Reged: 04/19/04

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Re: M57 central star? new [Re: Dwight J]
      #6139190 - 10/15/13 02:27 PM

DwightJ wrote:

Quote:

Some say the star is variable in brightness and this may play a role in it's visibility.




According to Brian Skiff of Lowell Observatory, professional photometry of the central star has given it a magnitude of about 15.0 with no evidence of any variability. Viewing the central star in M57 depends largely on the stability of the atmosphere, so if seeing isn't rock-solid, you won't see it no matter how big the telescope is. Clear skies to you.


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David Knisely
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Re: M57 central star? new [Re: brianb11213]
      #6139212 - 10/15/13 02:40 PM

brian11213 wrote:

Quote:

Point 3: I'm skeptical of the need for more than 20x per inch of aperture. It's at about this point that the diffraction disc of a point object (star) starts to become extended and there is no further gain in contrast between star & background by going higher. Smearing out the star tends to reduce its visibility in the same way that poor seeing does.




I performed experiments during good seeing, and the results were that unless the power is fairly high, the star remains invisible. In my 10 inch f/5.6 Newtonian, I was unable to see it if the power was less than 300x (I was at 288x when doing the experiment), and it was decidedly easier to pick up at powers above 350x. In fact, most of the time when trying for the star, I use from 384x to 471x even in my 14 inch. It just takes a bit more power to dim down the interior glow of the nebula and let the star stand out a bit more, especially considering the low resolution of the dark adapted human eye using averted vision. The consensus among most experienced deep-sky observers is that to see the central star, something over 300x is often necessary. Indeed, Brian Skiff has recommended something closer to 500x:

Photometry of M57 Field Stars

Clear skies to you.


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Dwight J
scholastic sledgehammer
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Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: M57 central star? new [Re: David Knisely]
      #6139222 - 10/15/13 02:45 PM

Thanks David for clearing up that variability issue for me. That just leaves steady air as the requirement (as well as a scope large enough to see 15th mag stars) to see the CS of M57. That certainly explains why seeing it is rare for me as my area of the world is plagued by poor seeing.

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brentwood
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Re: M57 central star? new [Re: Dwight J]
      #6139313 - 10/15/13 03:31 PM

"So how long ago was that? There hasn't been an eyepiece on the Plaskett in decades."
I think that it may have been before we moved to Victoria, so sometime before 1984. I am sure that was the time when the attending astronomer asked the audience if anyone in the audience knew where the various objects in the sky actually were so he could manually position the slit correctly!
For years, I simply wrote off my lack of a CS sighting to an idea that the scope was only transmitting a tiny portion of the aperture to the eyepiece for guiding purposes. It wasn't until we moved here and I had some of the astronomers as customers that I found out that this was not the case.
The next time we went, they had a camera in the eyepiece position and we viewed the image on a monitor. I remember that we were looking at M13 and I found that I was just tall enough to look through one of the old 5"? guidescope/finder that amazingly was not capped. To me this had a much better view! Soon we had a line up there!
Best viewing I ever had up on the hill was 10-12 years ago at a close Mars opposition, with the 48" through I think a coude focus. That was a real WOW! very steady seeing, and the disk was THIS big!


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payner
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Re: M57 central star? new [Re: David Knisely]
      #6139504 - 10/15/13 05:38 PM

Quote:


I performed experiments during good seeing, and the results were that unless the power is fairly high, the star remains invisible. In my 10 inch f/5.6 Newtonian, I was unable to see it if the power was less than 300x (I was at 288x when doing the experiment), and it was decidedly easier to pick up at powers above 350x. In fact, most of the time when trying for the star, I use from 384x to 471x even in my 14 inch. It just takes a bit more power to dim down the interior glow of the nebula and let the star stand out a bit more, especially considering the low resolution of the dark adapted human eye using averted vision. The consensus among most experienced deep-sky observers is that to see the central star, something over 300x is often necessary. Indeed, Brian Skiff has recommended something closer to 500x:

Photometry of M57 Field Stars

Clear skies to you.




That's been my experience, high magnification with excellent seeing ... steady skies with no twinkling of the stars. The point made about it coming into and out of view has been my experience too. Having the planetary near the zenith and the necessary seeing conditions are uncommon for most of us and makes it an event that one doesn't forget.

Best,
Randy


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blb
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Re: M57 central star? new [Re: David Knisely]
      #6139529 - 10/15/13 05:58 PM

Quote:

Quote:

Here is a magnitude chart of surrounding stars. If you can't see some of these, you won't see the center star.




Uh, that's MY chart BTW.... (prepared from a DSS image I processed with photometry provided by Brian Skiff of Lowell plus other sources).



David, I found that photo to be such a help that I saved it for future use. Sorry I did not give you the credit. You certainly deserve a lot of credit for all the help you provide. To be honest, I had forgot whose photo it was after having it for a couple of years. Sorry but thanks.


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bremms
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Re: M57 central star? new [Re: blb]
      #6139559 - 10/15/13 06:16 PM

The central star is quite blue.. Integrated magnitude may be 14.6- 15.0. Visual it is 15.8-16.0 or even fainter. A good bit of the energy is in the far blue end of the spectrum as the surface temperature is about 100,000K. If you are a little older it might be more difficult. The spectral distribution makes it difficult. That being said, I saw it one time from a green Zone 30 years ago in a 16" F5 Cave. Seeing and transparency were very good that evening.
We used a 5mm Clave' and a Barlowed 10.5mm RGO (mine) about 400x. It was not visible under about 300x.

Edited by bremms (10/15/13 06:28 PM)


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Dave Mitsky
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Re: M57 central star? new [Re: bremms]
      #6139578 - 10/15/13 06:28 PM

I was able to hold M57's central star fairly steadily at high power through John Vogt's homemade 32" Dob on one occasion.

Dave Mitsky


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Dave Mitsky
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Re: M57 central star? new [Re: Dave Mitsky]
      #6139580 - 10/15/13 06:30 PM

Please keep in mind the TOS regarding photographs.

Please do not copy e-mails, articles, pictures or posts from publications or from other online sites unless you are the owner of the material or have received explicit permission from the owner to do so. This permission must be included in your post. Using another person's work without permission is, at the very least, poor netiquette, and is not permitted on this forum. A summary or short quote is allowed without permission, but you must include the identity of the original source. The best way to direct fellow CN members to material you have found is to simply include a link, when possible, in your post.

http://www.cloudynights.com/ubbthreads/showflat.php/Number/233117

Dave Mitsky


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jhayes_tucson
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Re: M57 central star? new [Re: Dave Mitsky]
      #6139596 - 10/15/13 06:44 PM Attachment (4 downloads)

I was able to view it last Friday with C14, a Canon 7D, and 30 seconds of unguided exposure at ISO 6400. Total beginner's luck. (I couldn't see it visually, but then again, I didn't spend much time trying.)
John


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David Knisely
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Re: M57 central star? new [Re: bremms]
      #6139682 - 10/15/13 07:33 PM

Quote:

The central star is quite blue.. Integrated magnitude may be 14.6- 15.0. Visual it is 15.8-16.0 or even fainter. A good bit of the energy is in the far blue end of the spectrum as the surface temperature is about 100,000K. If you are a little older it might be more difficult. The spectral distribution makes it difficult. That being said, I saw it one time from a green Zone 30 years ago in a 16" F5 Cave. Seeing and transparency were very good that evening.
We used a 5mm Clave' and a Barlowed 10.5mm RGO (mine) about 400x. It was not visible under about 300x.




Ah, no not quite. The professional V-band photometry indicates a visual magnitude of the central star of about 15.0 with a few measurements 0.1 to 0.3 magnitudes fainter than this. The star has been seen in apertures of nine inches and larger, so that would suggest the 15th magnitude visual measurement to be fairly accurate. Clear skies to you.


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2orthern2ights
journeyman


Reged: 10/13/13

Re: M57 central star? new [Re: David Knisely]
      #6140052 - 10/15/13 11:33 PM

Thanks for the replies everyone. I'm off to bortle 1ish in a week. For certain, I'll be looking for that central star when I get there.

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blb
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Re: M57 central star? new [Re: 2orthern2ights]
      #6142934 - 10/17/13 01:13 PM

David wrote;
Quote:

...Viewing the central star in M57 depends largely on the stability of the atmosphere, so if seeing isn't rock-solid, you won't see it no matter how big the telescope is. Clear skies to you.



Does that mean that seeing any stars of 15th mag. and fainter is totaly seeing dependent even with larger telescopes. I mean, most people who have 18-inch to 24-inch telescopes have trouble seeing the central star. True?


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David Knisely
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Re: M57 central star? new [Re: blb]
      #6143402 - 10/17/13 05:45 PM

Quote:

David wrote;
Quote:

...Viewing the central star in M57 depends largely on the stability of the atmosphere, so if seeing isn't rock-solid, you won't see it no matter how big the telescope is. Clear skies to you.



Does that mean that seeing any stars of 15th mag. and fainter is totaly seeing dependent even with larger telescopes. I mean, most people who have 18-inch to 24-inch telescopes have trouble seeing the central star. True?




No, the problem is that the diffraction disk of the central star is imbedded in faint nebulosity. When the seeing blurs the disk, it then blends perfectly into that faint glow and vanishes. Outside of the ring against the dark background of space, a 15th magnitude star has little to compete with, although you will be able to see slightly fainter stars when seeing is very good. When I saw the central star from my driveway in my 9.25 inch SCT, I could see a magnitude 15.3 star well ouside the ring much of the time, but only occasionally when the seeing got really really good would the central star finally pop out. Larger scopes (10 inches and larger for example) will show stars fainter than 15th magnitude seen against the dark background of space when seeing isn't necessarily rock-stable, but when it comes to the central star in the Ring, unless seeing is very very good and relatively stable, no telescope no matter how large will show that star. Clear skies to you.


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Charles Funk
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Reged: 09/06/05

Loc: W. Tennessee
Re: M57 central star? new [Re: David Knisely]
      #6143625 - 10/17/13 07:58 PM

I have seen this winking in and out of stars in M42 on many occaisions. When you look long enough, it puts on an interesting show.

I have never tried seeing the CS in M57, but you can bet I will give it a whirl next time out. Just recently I observed M57 at around 300x on a whim and it was awesome in the 12.5 But I didn't think to look for the CS. I do like a challenge.


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Kfrank
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Re: M57 central star? new [Re: Charles Funk]
      #6145029 - 10/18/13 02:45 PM

Several people have described the central star as "fading in and out". This is due, essentially to the same visual phenomena that make 'the "Blinking Planetary" appear to blink.

Remember also that the "Ring" Nebula is not really a ring - it's roughly spherical in nature and simply appears to be a ring. We're actually looking at the center of the "ring" through the cloud of the nebula.


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David Knisely
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Re: M57 central star? new [Re: Kfrank]
      #6145791 - 10/18/13 10:58 PM

Quote:

Several people have described the central star as "fading in and out". This is due, essentially to the same visual phenomena that make 'the "Blinking Planetary" appear to blink.

Remember also that the "Ring" Nebula is not really a ring - it's roughly spherical in nature and simply appears to be a ring. We're actually looking at the center of the "ring" through the cloud of the nebula.




No, the "blinking" of the Blinking planetary (NGC 6826) is due to the difference between direct and averted vision in moderate to small telescopes. Looking directly at NGC 6826 may cause it to dim or nearly vanish, while using averted vision will allow it to be seen. The variable sighting of the central star of the Ring nebula is almost entirely due to seeing variations causing the central star's diffraction disk to be blurred. When this happens, it totally blends in to the surrounding faint nebulosity, rendering it invisible unless seeing is rock-stable, no matter how big the telescope is or whether averted vision is used or not. When I saw the central star in a 20 inch Dobsonian, I was able to use direct vision on it, as it was bright enough in that scope. When the stability of the seeing became degraded, the star vanished, again, for the reason stated above. Clear skies to you.


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Starry eyes
super member


Reged: 04/30/10

Re: M57 central star? new [Re: David Knisely]
      #6146339 - 10/19/13 10:20 AM

I would say seeing is the main criteria to see the CS.
When seeing is decent I can see it in my 18" Split Ring, flickering in and out @ 320x. A smooth drive helps. In a 30" it is visible pretty much all the time with good seeing.


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Skylook123
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Re: M57 central star? new [Re: Starry eyes]
      #6146370 - 10/19/13 10:33 AM

Up at 7000 feet about four years ago on one night of exceptional transparency and seeing at the Grand Canyon Star Party, Mike Spooner was able to easily show the central star in one of his awesome 14" mirrors in a home made Dobsonian mounted reflector. Even visitors never having looked through a telescope before were able to see it. Quite striking.

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