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Minimum aperture to observe M57 central star

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#1 kansas skies

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Posted 04 December 2012 - 09:47 PM

I'm new to this forum and would like to begin by saying hello to all. I've attempted many times over the years to glimpse the central star in the ring nebula and have never positively managed to do so. I was wondering if some of you that have seen this elusive central star visually might mention the minimum aperture and type of telescope used, as well as maybe give some details as to observing conditions at the time - tnx Bill.

#2 jgraham

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Posted 04 December 2012 - 10:22 PM

Welcome to Cloudy Nights!

We had a fun discussion of this very topic here...

http://www.cloudynig...5307648/page...

I've been trying with my 16" under my red zone skies and I think that I'm sooooo close. I get the impression of a brightening in the center, but I can't say for certain it's the star. I recently got my binoviewers working on my LightBridge, so I'll try again if I get a chance. In contrast, the central star of M27 is a snap, and quite beautiful.

Have fun!

#3 John K

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Posted 04 December 2012 - 11:47 PM

I caught this star this summer with my 15" scope on top of the mountain.The seeing was very steady.I was using about 500X.I was a game of Patience as the ring rolled through the field of view many times before it popped out and said hello.When you see it, it will be obvious and it comes in quiet sharp.It is a wow moment,then where did it go?I think the seeing is the most important thing to success.But magnification is also important.

Good luck!

#4 JayinUT

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Posted 05 December 2012 - 12:39 AM

My 14 and a friend's 16 both did it this summer.

#5 kfiscus

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Posted 05 December 2012 - 01:15 AM

Friend and I got it on an exceptional night on the meridian with my tracking Z12. You need great seeing and very high magnification.

#6 David Knisely

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Posted 05 December 2012 - 02:23 AM

Well, the smallest aperture I have seen the central star of M57 in was a 9.25 inch SCT at 480x on a night of very stable seeing, although it was tough and was only visible briefly and only for a few times that night. In fact, the main keys to seeing the central star are very very stable seeing and high power (more than 300x for example). A 10 to 12 inch aperture may be a good place to start as far as aperture is concerned, although again, larger apertures may make it a little easier to see when it does appear. I remember during college when we were at a public night at Behlen Observatory's 30 inch Classical Cassegrain located well north of Lincoln at UNL's Field Laboratory near Mead, Nebraska. The scope was on the Ring but the central star was not visible at any time. I asked my professor (Don Taylor) about that, and he said that he hadn't seen the central star even in Steward Observatory's 90 inch at Kitt Peak, so at the time, I concluded that it might not be possible to see in amateur instruments. A few years later, I learned the truth at one of our club star parties at our dark sky site south of Lincoln, Nebraska. A friend of mine called me to his 20 inch Obsession to "see the central star in the Ring". I kind of said, "Yea, right", so I went up the scope's big ladder and had a peek. Sure enough, at over 400x, there, sitting right in the middle of the ring was the central star, visible with direct vision! Then, abruptly, it vanished. I watched for a while and it faded in and out as the seeing varied, so it soon became obvious what was going on. Seeing was blurring the star to a point where it just blended into the glowing nebulosity in the interior of the Ring. If the seeing wasn't absolutely tack-sharp, the central star would almost never appear. Once I figured this out, I went back to my own ten inch and watched for a while, waiting for the seeing to finally settle down for at least a few brief moments. Eventually, I did manage to catch a few short periods when the seeing stabilized and the star briefly appeared in my own scope, although in the ten inch, it was still pretty faint. When visible, it sort of 'blinks' on and off as the seeing changes, so be prepared for that behavior. The main key to observing the central star is: if the seeing isn't great, the central star will not appear no matter how big the scope is. You have to watch the center of the ring at fairly high power (at least 300x to 400x) for quite a while and not just look in and just give up when you don't see it right away. Clear skies to you.

#7 MikeBOKC

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Posted 05 December 2012 - 09:02 AM

This is still near the top of my list, still unattained. All I have read says 14-16 inches, dark skies, very good seeing and high magnification . . . a rare combination for most folks. And patience . . . I understand it will pop in and out under even the best conditions.

#8 Feidb

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Posted 05 December 2012 - 10:02 AM

I've seen it twice, once with each of my 16-inch scopes. It's certainly not easy, takes high magnification and the right conditions. Not an easy task. As David says, it can be done with smaller apertures but magnification and conditions are key.

#9 kansas skies

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Posted 05 December 2012 - 12:16 PM

Thanks to all for these great replies. I guess it really isn't just me after all. I've tried to see the central star in scopes as large as 16", but it's always refused to show itself. These were scopes belonging to others, so the opportunity was not there to extract as much from them as I would've liked. The largest scope I own is an older orange tube Celestron C8, which I try to keep well collimated. It's the second C8 that I've owned, the first being a Super C8 that I bought in the early to mid 1980's. It might just be the stubborn side of me, but I've always felt like the central star should be visible, even if just fleeting, under the right conditions in a C8. Just what these conditions would be is the real question. I did read on the other discussion pointed out here that someone did manage to see it with an eight inch newtonian. This gives me hope. It sounds like magnification might be the ingredient I've been missing, since I find that the skies here in Kansas very rarely allow magnifications beyond 280x in my C8. Still, nights of fantastic seeing do occur occasionally, and I guess it may be on one of those nights that I might just get there. Of course, Lyra is pretty low in the western sky in the evening this time of year, so I guess I will have to wait until next season - Bill.

#10 Starman1

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Posted 05 December 2012 - 03:51 PM

I tried unsuccessfully for eleven years with an 8" SCT, and caught it for several "winks" in a 12.5" on the first night out.
Ditto the Horsehead Nebula, which i never saw with the 8", but see all the time with 12.5".
The first requires excellent seeing. The second requires excellent transparency and darkness.
And both require, I believe, at least 10" of aperture.

#11 kansas skies

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Posted 05 December 2012 - 05:15 PM

I'm afraid you might be right with the estimate of 10" minimum aperture, but for now I will have to keep trying with my C8. Hopefully, when the time comes to move up to something larger, the experience will pay off. On the other hand, if something is too easy, I tend to lose interest pretty fast. So, if I do move up, I'll probably just go looking for something else that is just outside my reach - Bill.

#12 Dave Mitsky

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Posted 05 December 2012 - 06:24 PM

You may find the articles at http://www.astropix....E_SUM_N/M57.HTM and http://www.hacastronomy.com/m57.htm of some interest.

I've only seen M57's central star a few times and that was through large premium Dobs at magnifications of 300x and greater.

Dave Mitsky

#13 blb

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Posted 05 December 2012 - 06:47 PM

First let me say welcome to this forum. It is good to hear from new people.

I saw the central star in M57, using my 10-inch dob a couple of years ago at 300x. It was a great night from a really dark sky site in the mountains of western NC. Kind of hard to keep up with the nebula in the dob at that magnification but the central star was plainly visible. That was the night that I learned that my scope could reach mag. 15.6 at that magnification. The central star is approximately mag. 14.8 but it is not all that easy to see because it is located within the nebula. Being in the nebula reduces the contrast and makes it much harder to see, so you will need a good dark site (green zone or better) and good seeing (atmospheric steadiness) with very high power to make this observation.

#14 David Knisely

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Posted 05 December 2012 - 07:20 PM

First let me say welcome to this forum. It is good to hear from new people.

I saw the central star in M57, using my 10-inch dob a couple of years ago at 300x. It was a great night from a really dark sky site in the mountains of western NC. Kind of hard to keep up with the nebula in the dob at that magnification but the central star was plainly visible. That was the night that I learned that my scope could reach mag. 15.6 at that magnification. The central star is approximately mag. 14.8 but it is not all that easy to see because it is located within the nebula. Being in the nebula reduces the contrast and makes it much harder to see, so you will need a good dark site (green zone or better) and good seeing (atmospheric steadiness) with very high power to make this observation.


Best photometry indicates that the central star of M57 has an approximate visual magnitude of between 15.0 and 15.2. Here is a good article by Brian Skiff of Lowell Observatory about the measured brightness of the stars in the area of sky near M57:

Photometry of M57 Field Stars

Seeing the central star does not necessarily require extremely dark skies, although the sky should not be terribly light polluted either. I have seen it with my 9.25 inch from my front driveway (ZLM 5.5 - 5.8 on a moonless night). However, seeing it does require very very steady seeing and rather high power to get it to appear. The high magnification generally reduces the brightness of the faint nebular glow in the interior of the ring which helps the central star stand out a little better. I recommend around 400x or so (and Brian Skiff likes around 500x), but some have seen it at between 300x and 400x. Clear skies to you.

Clear skies to you.

#15 kansas skies

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Posted 05 December 2012 - 09:38 PM

I read both of these very informative articles and then consulted notes I made awhile back during one observing session. I had my C8 and my 127mm Mak set up side by side for comparison purposes. Using the star magnitudes indicated in these articles, I found the 13th mag star easy and steady in both scopes, but much brighter in the C8. The two 14.1 mag stars were faint but steady with averted vision in the C8, but not there in the Mak. It looks as though the 14.7 mag star was popping in and out. Given that my normal observing site (my backyard) rarely goes below 5 to 5.5 naked eye magnitude, I think a really dark site might drop me down the half magnitude that I would need. Of course, having the target star planted in the middle of the nebula might be a bit of a hindrance, but I still think I can get there someday. I guess that even if I never see the central star, the Ring Nebula is still one of my favorite deep sky objects due to its almost 3-dimensional quality that shows in just about any scope I've observed it with. It's very easy to see and show - tnx, Bill.

#16 Tom Polakis

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Posted 06 December 2012 - 02:17 PM

Great replies so far, with many of them mentioning high magnifications. That's the only way I have been able to see the central star fleetingly in my 10". Since you're using high magnification, a tracking telescope would give you a big advantage. Seeing is almost as important as sky darkness and transparency, since poor seeing can spread the light of faint stars out to invisibility.

We really should be having this discussion four or five months from now, as it's currently too low to get a clear view.

Tom

#17 hbanich

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Posted 08 December 2012 - 01:46 AM

I've always a tough time seeing M57’s central star in anything smaller than a 16 inch but then I never had the really steady seeing needed to see it when I used smaller scopes. A little research shows that the central star was discovered around 1795 by Friedrich von Hahn with a 12 inch speculum mirror (made by William Herschel) which would at best have the reflectivity of a modern 10 inch reflector. It must have been an exceptionally steady night to discover such a faint star in this scope, which underscores that steady seeing is more important than the type or size of the scope.

#18 kansas skies

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Posted 08 December 2012 - 08:37 AM

Subtract a few billion watts worth of artificial lights and I suspect the capability of a 12" speculum mirror might be surprising.

#19 blowe

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Posted 08 September 2013 - 08:16 PM

Shoot, I just found m57 for the first time last night, let alone the central star...






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