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DanyalAG

Can you really see +7 magnitude stars with your eyes in bortle 1 or 2 skies?

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This fact comes up quite a lot on the internet. Recently, I was reading a Sky and Telescope magazine article, and it stated that Stephen o Meara was able to see better than 7, and on some occasions even 8 magnitude stars with his naked eye alone. Is this possible? I find it very hard to believe because I've observed from Bortle 3-4 sites on a couple of occasions, and the best I could do was about mag 6.3 (with considerable effort). I am by no means an expert, and have only been involved in amateur astronomy for the best part of 2 years, but still, I know most of the techniques like dark-adaptation, averted vision and I still couldn't do any better. I have excellent eyesight (better than 20/18 in my right eye) but still, such a feat seems impossible to me. I mean no disrespect to o Meara, however is there anyone here who has observed from perfect (Bortle 1 or 2) sites and was able to replicate o Meara's feat? If not, why don't you give the faintest magnitude you've ever seen. Just a curious question on my part...

Any replies are welcome.

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Steve's eyesight is legendary.  There is always someone somewhere that can see fainter, hold their breath longer,  or run faster than most.  For the average observer with good skies +6 mag is quite good going for naked eye.  Don't forget that each magnitude increment is roughly 2.6x fainter.    🙂  

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Seeing faint stars is different to how sharp your eyes are.  The former partly depends on your maximum pupil size, that tends to decrease with age, plus of course on light pollution and sky clarity.

Unfortunately the maximum pupil size in my better eye is only 4.5mm (7mm is more typical for young people) and so my naked eye limiting magnitude is well below average.

On the other hand I have very sharp vision with glasses: 6/4 in each eye, that corresponds I believe to 20/12 old style.

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20 minutes ago, Second Time Around said:

Seeing faint stars is different to how sharp your eyes are.  The former partly depends on your maximum pupil size, that tends to decrease with age, plus of course on light pollution and sky clarity.

Unfortunately the maximum pupil size in my better eye is only 4.5mm (7mm is more typical for young people) and so my naked eye limiting magnitude is well below average.

On the other hand I have very sharp vision with glasses: 6/4 in each eye, that corresponds I believe to 20/12 old style.

Oh, well I wasn't really aware of that fact. Thanks for the info. However, i do think that o Meara wasn't quite young (at least 35-40) when he did all those things.Anyways, what's the best you've been able to do?

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1 hour ago, DanyalAG said:

Anyways, what's the best you've been able to do?

About mag 5.5 with averted vision on the clearest of nights here at home.  However, we're low lying and so get a lot of mist (and dew).  We're supposed to be Bottle 4 here, but I have my doubts.  

It seems about the same as when I lived in the suburbs of London.  But I was a teenager then.

Of course increased light pollution is likely to be a big factor in addition to my poor pupil size now I'm an old man.

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I find point stars harder to see to low brightness than extended sources. From my location the Milky Way is quite bright and structured, even the winter Milky Way is well defined, yet my limiting mag is well short of what it should be.

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Posted (edited)

There are (at least) two factors that determine dark-seeing ability. Visual acuity - just how well your eye can possibly focus light to a  spot, and maximum pupil size - which determines how much light gets in to the eye.

I suppose it might just be possible for someone with exceptional values for both of those to see that deep, but it would be very rare. We all know that pupil dilation reduces with age. The older you get the smaller your max. dilation becomes. So even discounting sky darkness, what textbooks state as biological possibilities would almost never translate into individual cases.

My location occasionally gets down to an SQM reading of 22. But on those rare occasions I can't say that I can see anything fainter than when it is in the mid 21's, such is the state of my eyes.

Edited by pete_l
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This is something I've been meaning to try just to see what my eyes can pick up. I was under 21.80-21.85 skies last night, a solid Bortle 2 approaching Bortle 1 territory, and it seems like everything is visible, just right there... The flying minnow asterism in Auriga was directly observable, that's always a good sign to me. Need to check magnitude on those stars. Hoping to go back tonight in the wee hours if possible. 

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Mr O’M has better eyes than me. 

Mag 6 is doable with dark sky and ok eyes. I was under darkest sky in Namibia a couple of weeks ago. 😳😮😮What a difference! Still not mag 7 with my eyes.
Paul

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I can see mag 6.8 NELM from my homes skies under the best conditions.

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We once 'tested' a guest here to confirm that he really could see Mag 7.  He could. (We had a star chart, picked a lonely mid magnitude naked eye star with the laser, and asked him to describe the starfield around it.)

Another legend, indeed the legend, was E.E.Barnard. Two professional colleagues once called him to the eyepiece to ask him to confirm or deny a new possible double. His reply was something like, 'Yes, yes, clearly a double and the westerly component is itself a double.' (Source What Immortal Fire Within,  William Sheehan.)

One of my standard jokes here is, 'It's so faint that even Barnard had to wait till dark before he could see it naked eye...'

😄lly

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12 hours ago, Paul73 said:

Mr O’M has better eyes than me. 

Mag 6 is doable with dark sky and ok eyes. I was under darkest sky in Namibia a couple of weeks ago. 😳😮😮What a difference! Still not mag 7 with my eyes.
Paul

I'd love to visit Namibia. That's been on my list for a few years now. Did you take binoculars or did your lodgings have a scope?

Toyota Land Cruisers (especially old ones and any of the 70 series) are my other weak spot besides astronomy, so I'd imagine there are a few kicking about there.

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Posted (edited)
1 hour ago, Ships and Stars said:

I'd love to visit Namibia. That's been on my list for a few years now. Did you take binoculars or did your lodgings have a scope?

Toyota Land Cruisers (especially old ones and any of the 70 series) are my other weak spot besides astronomy, so I'd imagine there are a few kicking about there.

I only had my 10x50’s, but had fun with those. We had a Land Cruiser with tents on top. 😁. Drives like a tractor, but will keep going through anything!
Great trip.
Paul

23901238-DD30-46AD-BB9D-A5897A938E10.jpeg

Edited by Paul73
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I use Ursa Minor to test my eyes and compare the sky quality because it contains a handy range of star magnitudes.  In Cornwall under good skies Bortle class 2 and 3 I can see down to slightly better than mag 5. I can't see mag 6, even with averted vision. I can see M31 though in a clear night, but only with averted vision. 

 

image.gif

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A good test of the eyes is the Double Double- I easily see it as 2 stars naked eye- anyone else?

Using Umi for NELM is easy and is what I use but when the bowl is low I think the NELM understates the true limiting mag. If I was better at this I would know stars to use at zenith, which is worth a bit more IMHO.

Personally, once a dark site is established not much time is spent (wasted) on this- its right to the scope. The appearance of the Milky Way is the fastest best guide IMHO.

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1 hour ago, jetstream said:

A good test of the eyes is the Double Double- I easily see it as 2 stars naked eye- anyone else?

I have seen it naked eye on a couple of occasions, but it requires dark skies.However, in my opinion Mizar and Alcor is a finer test of visual acuity(at least for me).

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Posted (edited)
5 hours ago, Paul73 said:

I only had my 10x50’s, but had fun with those. We had a Land Cruiser with tents on top. 😁. Drives like a tractor, but will keep going through anything!
Great trip.
Paul

 

Ah yes, love the photo. That's a 70 series tray-back Ute! The 70 series are legendary, but they don't sell them in the UK or Europe, though a few imports squeak through. They used to sell the LJ70 series here, but stopped in 1993. I had a 1988, they are worth a small fortune now for one in good nick but rare as rocking horse poo. If they did import the new 70 series, you'd probably be looking upwards of £60k for one. Not really practical unless you have a farm or work offroad of course!

Sorry to go off topic, I want to try Ursa Minor tonight if we get a clear spell and compare it to my SQM meter. 

 

Edited by Ships and Stars
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It has been my fortunate privilige  some 25 years ago to visit some of the world's best sites at Las Campanas Chile, Sutherland in South Africa and others. You certainly can see to mag 7. Not just that, the number of Messier objects usually reserved for binoculars which are easily seen by the naked eye is astounding.  M33 is easy if low towards the north, ditto M92 and many others. I always found it harder to spot well-known constellations because the first and second magnitude stars get lost in the myriad of smaller ones. And then there is the Milky Way which starts to look like a photograph, and Venus casts a shadow on to paper.

Aperture may be king but site is the ace..

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Posted (edited)

I have split epsilon Lyrae naked eye, but not since I was a youngster. My eyes are just too damn rubbish now though my distance glasses do make a difference.

Last autumn I did see NGC 752 which Stellarium said was 5,86 due to air mass., while point stars at that mag were not visible.

Edited by DaveS
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I used to be able to split Epsilon Lyrae naked eye, count 14 stars in the Pleiades and spotting M33 was a test for the seeing conditions.  Sadly, age has taken its toll and I can no longer even split Mizar and Alcor naked eye.     🙁    

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I think I can still just split Mizar and Alcor, on a good night when they're near the zenith.

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44 minutes ago, Peter Drew said:

I used to be able to split Epsilon Lyrae naked eye, count 14 stars in the Pleiades and spotting M33 was a test for the seeing conditions.  Sadly, age has taken its toll and I can no longer even split Mizar and Alcor naked eye.     🙁    

Should've gone to SpecSavers? ;)

I needed glasses for decades to drive and see the sky.
I couldn't read a clock on the office wall without my specs.
There were only soft blobs up in the sky.
After retirement my eyes relaxed to perfect, distance vision.
Sheer luck, but it certainly stopped the moon being a "close double." :)

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4 hours ago, Ships and Stars said:

I want to try Ursa Minor tonight i

Try 20 Umi at 6.4ish and if trans is top at 21.8mag 17 Umi should be visible or 8 Umi. Good luck!

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3 hours ago, Rusted said:

Should've gone to SpecSavers? ;)

I needed glasses for decades to drive and see the sky.
I couldn't read a clock on the office wall without my specs.
There were only soft blobs up in the sky.
After retirement my eyes relaxed to perfect, distance vision.
Sheer luck, but it certainly stopped the moon being a "close double." :)

The eye lens hardens and changes shape as you get older.  If you are lucky, as you seem to have been, it can correct some vision problems.     🙂

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