21 replies to this topic

[blb]

Wow, I just found a picture at the bottom of the forum that had the magnitude of stars around M57. I was looking at M57 last night with my 10" Dob at 300x. If that picture is correct, well then I could see stars to mag 15.6 with averted vision. Could this be true? I also thought that I saw the central star a couple of times with averted vision. I could not hold the central star but for maybe 40% of the time. I did not think this was possible with a 10" reflector. You tell me, was it averted imagination or do you think I may have seen it?

Buddy

[David Knisely]

Wow, I just found a picture at the bottom of the forum that had the magnitude of stars around M57. I was looking at M57 last night with my 10" Dob at 300x. If that picture is correct, well then I could see stars to mag 15.6 with averted vision. Could this be true? I also thought that I saw the central star a couple of times with averted vision. I could not hold the central star but for maybe 40% of the time. I did not think this was possible with a 10" reflector. You tell me, was it averted imagination or do you think I may have seen it?

Buddy

On a good steady night with minimal skyglow, a 10 inch should get you into the low to mid 15's in magnitude if you use moderate to high power (between 180x and 500x). The central star is around 15.2 or so, but unless seeing is rock-steady, it tends to blend into the glowing background in the interior of the Ring Nebula. When seeing settles-down, it will become visible at least briefly, or 'flash' on and off as the seeing gets better and then worse. If seeing isn't really stable, no telescope will show it. I have managed about 15.6 with my NexStar 9.25 inch SCT, but it took an outstanding night to do that. Below is a chart of the M57 region with some star magnitudes listed (the decimal point is omitted, so a figure like "156" means magnitude 15.6). Clear skies to you.

Attached Thumbnails

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[JakeSaloranta]

I was looking at M57 last night with my 10" Dob at 300x. If that picture is correct, well then I could see stars to mag 15.6 with averted vision. Could this be true?

I would hope so. I all depends on sky conditions, your eyes (age), experience and so forth. I'd consider reaching 15.6 magnitude with a 10 inch telescope to be quite normal and you should nearly fly into the 16th magnitude under good conditions.

I often pass the 15th magnitude barrier with my 4.7" and 4.1" telescopes on a good night from a dark observing site. And no I don't have anything but a normal eye sight. My lady has looked through a telescope maybe a handful of times during her life and she could easily see a 14.2 magnitude star with the same 4.1" telescope on a same night using poor quality eyepieces and full moon rising.

I also thought that I saw the central star a couple of times with averted vision. I could not hold the central star but for maybe 40% of the time. I did not think this was possible with a 10" reflector. You tell me, was it averted imagination or do you think I may have seen it?

In my experience the central star requires more magnification to see than, and I'm assuming you used, 300x. I've seen it a few times but only using magnifications over 600x.

[BillFerris]

Hi Buddy,

Under excellent dark skies, a 10 inch aperture is definitely capable of revealing mid-15th magnitude stars. It's not trivial--not by any stretch--to go that deep but is most definitely doable. Here's a link to observations of this field I've made with 10 and 18 inch telescopes: M57 Central Star Observations.

The central star was detected with averted vision in my old 10 inch, f/4.5 Meade Starfinder. It's a fairly easy direct vision object in my 18 inch Obsession. But getting back to observations with moderate apertures, I find the trio of 14.7 to 15.7 magnitude stars pointing towards the western edge of M57 to be a good measure of conditions for the detection of the 15.2 magnitude central star. If the 15.7 magnitude star at the apex of this right triangle asterism can be seen, the central star also stands a good chance of being detected. Though half a magnitude brighter, the central star resides amidst the delicate nebulosity filling the ring. And this makes the central star a more challenging target.

The 15.6 magnitude star you reference also serves as a good indicator. Seeing this star should encourage one to go for the central star. And if you detect the central star, give nearby IC 1296 a go. I've only seen this in my 18 inch but there are reliable reports made with smaller apertures.

Bill in Flag

[blb]

I guess this surprised me because most of the time I have not used this scope at a site this dark or with this much magnification. I simply was not expecting to see stars this dim. I have looked at M57 all my life and had never gone this deep before, thanks to light pollution. I am so familiar with the field that seeing this deep surprised me.

Buddy

[HellsKitchen]

Wow, I just found a picture at the bottom of the forum that had the magnitude of stars around M57. I was looking at M57 last night with my 10" Dob at 300x. If that picture is correct, well then I could see stars to mag 15.6 with averted vision. Could this be true? I also thought that I saw the central star a couple of times with averted vision. I could not hold the central star but for maybe 40% of the time. I did not think this was possible with a 10" reflector. You tell me, was it averted imagination or do you think I may have seen it?

Buddy

Yes, you most certainly did see it. I regularly hit Mag 15.5 with my 12" dob from my outer suburban skies. Infact, a couple of galaxies I observed just now from my backyard have blue magnitudes of 16 or so.

[Starman1]

Hi Buddy,

Under excellent dark skies, a 10 inch aperture is definitely capable of revealing mid-15th magnitude stars. It's not trivial--not by any stretch--to go that deep but is most definitely doable. Here's a link to observations of this field I've made with 10 and 18 inch telescopes: M57 Central Star Observations.

The central star was detected with averted vision in my old 10 inch, f/4.5 Meade Starfinder. It's a fairly easy direct vision object in my 18 inch Obsession. But getting back to observations with moderate apertures, I find the trio of 14.7 to 15.7 magnitude stars pointing towards the western edge of M57 to be a good measure of conditions for the detection of the 15.2 magnitude central star. If the 15.7 magnitude star at the apex of this right triangle asterism can be seen, the central star also stands a good chance of being detected. Though half a magnitude brighter, the central star resides amidst the delicate nebulosity filling the ring. And this makes the central star a more challenging target.

The 15.6 magnitude star you reference also serves as a good indicator. Seeing this star should encourage one to go for the central star. And if you detect the central star, give nearby IC 1296 a go. I've only seen this in my 18 inch but there are reliable reports made with smaller apertures.

Bill in Flag

IC1296 is usually visible in my 12.5" under mag.21.4 skies.
Under the same skies and using the same sequence, I usually see the mag.16.6 star near M57 without using averted vision, or by using averted vision hold it 100% of the time.
In a deeper sequence around M57, I can usually capture the mag.16.8 star, but never have I seen the mag. 17.3 star. So I have fairly reliable data that for my eye in my sites, mag.17+/- is about my limit (independent confirmation with stars in NGC206 & M14).
In the same skies, a 10" should reach past mag.16, so the mag.15.6 star is expected.
Your ultimate limit is based on what you can see with averted vision only about 10% of the time. Using magnitude charts, and KNOWING a star is there will often come up with a "at the limit" observation. In my experience, if you do not KNOW it's there, such a fringe observation would be unlikely. There can be several tenths difference from one night to the next, and seeing enters into the picture--faint stars are easier in good seeing.
Lots of variables.
It's good to push the limits, huh?

[Astrojensen]

It's good to push the limits, huh?

Pushing the limits is a lot of fun! With my Zeiss Telemator I've gone as deep as 13.6 on stars, if not one or two tenths deeper, while with my 85mm Zeiss, I've been fainter than 14 while hunting globulars in M31.


Clear skies!
Thomas, Denmark

[F.Meiresonne]

Well, I am not so lucky.

In my skies the central star in M57 is difficult. I have seen it on more then one occasion but is difficult and depends just on the seeing. When the seeing is good the 18" will show it in mag 5.5 skies. I have not seen it from my backyard though.
And as for stars around M57. If i can get to m15.7,i am lucky over here.
In the Provence I can see over m16, but over there the seeing is not always good either.

[blb]

Freddy,
I am 62 and this was the first DSO that I found that I had to look for to see it, that was in 1964. In 46 years this was the first time that I thought I had found it and felt comfortable that I had seen it. I was resolved to never see it and wasn't trying to. Surprise! You just never know sometimes what will happen when you take advantage of the seeing when available.

Buddy

[planetman83]

With my 8inch dob I saw the 15.7mag star but the central star was not there on an outstanding night at 1500 metres high. The same night I saw the central star with an 12".

2 days ago I tried again from the same site with my new 16" and at 360x I got some flashes of the central star and the dimmest star I could glimpsed was the 16.6mag star but this night was not so good.

[lymorkiew45]

The limiting magnitude for an 8" scope is 15.2, so seeing a half magnitude fainter must have been difficult, but obviously not impossible. The limiting magnitude for a 12" is 16.1, which could allow you to see that same 16.6 magnitude star in slightly better skies, but that 16.6 magnitude point of light is quite a stretch even for a 16" scope. I've seen the central star in my 12" scope, and it's far more difficult then that slightly fainter 15.7 magnitude star, and nearly impossible if the conditions are not perfect...clear skies...

[blb]

The limiting magnitude for an 8" scope is 15.2, so seeing a half magnitude fainter must have been difficult, but obviously not impossible. The limiting magnitude for a 12" is 16.1, which could allow you to see that same 16.6 magnitude star in slightly better skies, but that 16.6 magnitude point of light is quite a stretch even for a 16" scope. I've seen the central star in my 12" scope, and it's far more difficult then that slightly fainter 15.7 magnitude star, and nearly impossible if the conditions are not perfect...clear skies...

I am guessing that this was a typo, because I said that I was using my 10 inch Dob, not an 8 inch. The star that I observed, which is shown on David's photo above, is magnitude 15.6, not 16.6 . Just trying to not lead anyone astray with what I saw. You are correct, this was a difficult observation, of sorts. Note that I said that the central star was only seen with averted vision and only for a portion of the time. This star came in and out of view as the seeing varried.

Thanks,
Buddy

[David Knisely]

The limiting magnitude for an 8" scope is 15.2, so seeing a half magnitude fainter must have been difficult, but obviously not impossible. The limiting magnitude for a 12" is 16.1, which could allow you to see that same 16.6 magnitude star in slightly better skies, but that 16.6 magnitude point of light is quite a stretch even for a 16" scope. I've seen the central star in my 12" scope, and it's far more difficult then that slightly fainter 15.7 magnitude star, and nearly impossible if the conditions are not perfect...clear skies...

I am guessing that this was a typo, because I said that I was using my 10 inch Dob, not an 8 inch. The star that I observed, which is shown on David's photo above, is magnitude 15.6, not 16.6 . Just trying to not lead anyone astray with what I saw. You are correct, this was a difficult observation, of sorts. Note that I said that the central star was only seen with averted vision and only for a portion of the time. This star came in and out of view as the seeing varried.

Thanks,
Buddy

There are no hard and fast limits on magnitude, although for many people, an 8 inch will kind of max out around 14.8 to maybe 15.3 or so, depending on the skies and the sensitivity of the observer's eye. The magnitude 15.6 star I saw in my NexStar 9.25 was only visible part of the time when the seeing was really stable, and it was mostly on the threshold of visibility when I could see it. The magnitude 14.7 star just northwest of the Ring was visible pretty much all the time and the 15.3 guy was visible around half of the time, but fainter stars were only visible for fairly limited moments. Clear skies to you.

[planetman83]

I think that lymorkiew45 was talking about me. I managed to glimpse the 15.7m with the 8" but this night was the best night I have ever seen at the best site on my island, just 200 metres below a 1.3metre observatory. The same night I could not see the central star with the 8" but I did with a friend's 12". I think that the 15.7m star is easier than the 15.2m central star because of the nebulosity.

Also, the detection of the 16.6m star was with my new 16" but this night was not as good as the other one. The central star was glimpsed some times, maybe the seeing was not as good.

[JakeSaloranta]

The limiting magnitude for an 8" scope is 15.2, so seeing a half magnitude fainter must have been difficult, but obviously not impossible.

That does not count for the probability of detection of the human eye. The chance of detecting a 15.2 magnitude star with an 8 inch telescope is 50% and a 16.2 magnitude star is 10%. Then there's of course the way you're observing. If you're really trying the limiting magnitude of your telescope - you probably can go deeper than just looking for a faintest star in your sketch or something similar.

Seeing a 15.7 magnitude star with an 8 inch telescope means the observer knows what he is doing and the observing conditions are good. Under superb conditions the same telescope should show some 16th magnitude stars as well! I find it hard to believe that my 4.7" scope can show stars down to maybe 15.2 magnitude but my 8" stops at 15.7 - 16.

In the end, this kind of "who can see the faintest" hardly provides us with truthful numbers. It is like at the gym when someone asks you how much you bench press

/Jake

[Bill Weir]

After I read this guys story I decided that just about anything was visible. It's all in the eyes. Or technically what might not be in the eye. http://www.deepskyey...dex.php?gtype=l

It bugs the heck out of me, when people say what I have or have not seen.

Bill

[David Knisely]

JakeSaloranta posted:

That does not count for the probability of detection of the human eye. The chance of detecting a 15.2 magnitude star with an 8 inch telescope is 50% and a 16.2 magnitude star is 10%. Then there's of course the way you're observing. If you're really trying the limiting magnitude of your telescope - you probably can go deeper than just looking for a faintest star in your sketch or something similar.

One can't even say this much with any certainty. Some people will *never* see much past 14.7 in an 8 inch, while others may creep a little past 15th magnitude at the 50% observation level (i.e. the star is visible about half the time you are looking for it, which is what that percentage actually means). There is just no way to assign an absolute limit (even with probabilities). Most people will probably not go fainter than 16th magnitude in an 8 inch even under fairly good conditions, but the low 15's would be a definite possibility. Clear skies to you.

[JakeSaloranta]

One can't even say this much with any certainty. Some people will *never* see much past 14.7 in an 8 inch, while others may creep a little past 15th magnitude at the 50% observation level (i.e. the star is visible about half the time you are looking for it, which is what that percentage actually means). There is just no way to assign an absolute limit (even with probabilities).

Which was kinda my point. Nobody can really say "you cannot see past X magnitude with that telescope because I can't". Beauty of visual observing!

/Jake

[azure1961p]

I havent had the privledge, though miracle is a better descrition of M57 central star through my 8" reflector. I am pleased to see however that with just a little more diameter, " a lot" of folks seem to pick it.

Most know this, but for those who arent familiar with the onslaught of doubt, be forwarned: folks who have seen M57 withg HUGE optics [40" comes to mind} have NOT been able to make the central star. As a result , some are bitterly adamant that based on that, all those who claim to see it in medium apertures are over using there imagination.

I think the meart and potatoes here is that you need a scope that is large enough to "bring it in" but one also that is capable of atleast producing a reseanably crisp and proper stellar image. Large medium apertures seem adept at hitting this zone while gargantuan optics perhaps are so compromised by the seeing distroting stars way way beyond what could be called a "proper" diffraction poattern that there star, however much brighter is litarally blended away into the gauzzie grey of the Nebulas delicate central regions.

My hats off to all of you on this stellar "trophy". LOL, just be prepared for doubting observers. Its a tough crowd!!

Pete

David, hope all has been well.

[David Knisely]

I havent had the privledge, though miracle is a better descrition of M57 central star through my 8" reflector. I am pleased to see however that with just a little more diameter, " a lot" of folks seem to pick it.

Most know this, but for those who arent familiar with the onslaught of doubt, be forwarned: folks who have seen M57 withg HUGE optics [40" comes to mind} have NOT been able to make the central star. As a result , some are bitterly adamant that based on that, all those who claim to see it in medium apertures are over using there imagination.

I think the meart and potatoes here is that you need a scope that is large enough to "bring it in" but one also that is capable of atleast producing a reseanably crisp and proper stellar image. Large medium apertures seem adept at hitting this zone while gargantuan optics perhaps are so compromised by the seeing distroting stars way way beyond what could be called a "proper" diffraction poattern that there star, however much brighter is litarally blended away into the gauzzie grey of the Nebulas delicate central regions.

My hats off to all of you on this stellar "trophy". LOL, just be prepared for doubting observers. Its a tough crowd!!

Pete

David, hope all has been well.

Well, those who know the hows and whys of viewing M57's central star (stable seeing, the use of very high power, and patience) can easily shrug-off any people who make claims that this is impossible in 8 to 10 inch apertures. It is mainly a question of high power and seeing. If the seeing is less than stable, the Airy disk of the central star get blurred, becoming more diffuse. This causes it to blend into the glowing background of the middle of M57, often rendering it totally invisible, no matter how large an aperture is being used. Indeed, if the power is also too low, the core brightness of the nebula also tends to overwhelm the central star, so powers well over 300x are vital in any attempt to catch it. I recall my Astronomical Instrumentation Techniques professor (Don Taylor) saying he had never seen the central star even in the Steward Observatory (Kitt Peak) 90 inch telescope, and again, the reason is that when he was looking, the seeing wasn't really very stable.

When I finally got to view M57 in Behlen Observatory's 30 inch Classical Cassegrain, it did not show the central star, so I assumed from that point on that the star was simply impossible in amateur instruments. How wrong I was! A few years later at a club star party, one member yelled at me to come up and see M57's central star in his 20 inch f/5 Obsession. I scoffed, but I went up the ladder and had a peek. I was stunned to see the star shining nicely in the middle of the Ring with direct vision! However, the thing that finally got me to really understand was watching the darn thing for a while. At times, I saw the star abruptly fade out completely, and then quickly reappear as if someone had flipped a switch and turned it back on. Once I saw this, I could see that disturbances in the seeing were blurring the star's Airy disk and making it almost instantly blend into the faint glowing background of the middle of M57. There were even periods when the star was completely invisible or was "blinking" on and off with the seeing variations, so I finally had an idea of how the star sort of "behaved".

With that knowledge in-hand, I went back to my 10 inch, kicked the power way up (400x), and watched for a while. Sure enough, every once in a while, the star would very faintly pop into view for a few moments before vanishing again. I managed to catch it in my 9.25 inch SCT for the first time last year, so I could easily believe that a good 8 inch aperture under good conditions might possibly show it (although 8 inches is probably close to the minimum aperture that might show the star). If someone wants to see M57's central star, they need to use well over 300x and observe for quite a while to catch those brief moments when the seeing gets really good. Doing this will give people a fighting chance of catching this elusive star. Clear skies to you.

[timokarhula]

I have only once got an excellent view of the central star in the Ring Nebula. I obtained a 21-inch telescope in the summer of 2005. We have bright summer nights here in Sweden (latitude 60 N). One night in August, while it was not yet astronomically dark (solar elevation only -13°.1, that is nautical twilight) I pushed the magnification up to 435x, and voilá, the central star was staring right at me! Never ever had I seen the central star in M57 as well as now. It was visible about 50% of the time with direct vision. As David Knisely described, it vanished for some times and then reappeared again. At the same time I glimpsed a star of V=16.4 in the neighbourhood (that is in twilight!).

/Timo Karhula