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Sedna

Does anyone use eye glasses *just* for astronomy?

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Does anyone here use eye glasses *only* for astronomy? I'm a young guy with good eye sight. But here's a story that makes me wonder if I need eye glasses.

I went to Death Valley National Park in early November last year (2017), just about three weeks after Uranus was at opposition. I set up a modest (~2 inch) telescope I had borrow from a friend at Ubehebe Crater, which is at the northern end of the park. The northern end of park has a virtually perfect sky. If you check lightpollutionmap.info, this site is a Bortle class 1 sky, artificial brightness = 0.17 ucd/m^2. In other words, this was the best possible place and time to see Uranus.

In fact, I did find Uranus, but only with the aid of the telescope and a star chart app that told me exactly where to look. The app had enough background stars that I could identify Uranus through the scope, and it had the same blue color as in Voyager pictures. (Later that night I even found Neptune!)

But I also wanted to see Uranus with my unaided eye. This was my best chance, and how cool would that be, to say you really saw the seventh planet with your own bare eyes? Unfortunately, even when I knew exactly where to, I had no such luck. Some of the main stars in Pieces (where Uranus was) were even so dim that I could barely see them with averted vision (and even then I had to kinda wonder if I was only imagining seeing them).

Why I couldn't see Uranus near opposition in Death Valley, with a clear, dry sky and no light pollution and knowing exactly where to look? My best guesses are (1) vision problems and (2) eyes never fully dark adjusting.

1) I'm in my late 20s and don't wear glasses. Last I checked, I had 20/20 vision. But maybe I've become very subtly near sighted (my job involves staring at a computer screen all day).

2) I was checking the star chart app fairly frequency to orient myself. Maybe my vision never fully adjusted? I think I must have gone at least 20 minutes without looking, which should be enough to fully adjust?

I've also had some difficultly seeing M31 and other "easy" targets with the naked eye. I really don't think I can get a prescription for eye glasses from the doctor, because I see fine in daily life and had mine checked about a year ago (no problems).

So my question: Does anyone here use eye glasses *only* for astronomy? If so, where do you get a good pair? I really want to experience the joy of astronomy with my bare eyes and not just the telescope. If anyone has insights here, please let me know. Thanks everyone!

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I can't answer your question directly (I do use glasses, but not for astronomy - old eyes!) but some things spring to mind. 

To fully dark adapt takes quite a while - can be 20 minutes or more.  Any artificial light (and that includes red light) will hinder this process.  So will the moon, if present.  So looking at star charts, tablets, phone screens &c will reduce ability to make out dim stars. 

According to Stellarium, Uranus was Mag 5.7 last November so, as you say, should be visible to the naked eye.  But as a test, try Eta UMa (the faint star in the 'little dipper' bowl). This is mag 4.9, if you can make this out without too much difficulty, then your vision is OK.  There's a much more detailed tests here https://www.skyandtelescope.com/astronomy-resources/astronomy-questions-answers/naked-eye-magnitude-limit/ which might be worth trying before going for corrective spectacles?

 

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Ah, thanks, I will try calibrating with Eta UMa and the Great Square! It was a new moon when I looked for Uranus last November. I truly had the best viewing conditions imaginable, which makes me all the more disappointed I didn't see it with my naked eye :(

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Hi Sedna,

As Uranus is near the limit of naked eye visibility and since there are many factors including atmospheric seeing that can affect  our ability to see down this limit, I don't think you should be all that disappointed. If your vision is 20/20 then there is not much chance any kind of glasses will help.

Best

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I'm 44 yrs old. I wear glasses 24/7 for tv etc. I never wear them when observing. I just find them too uncomfortable and cant get close enough to the EP. 

I have a teeny tiny astigmatism in my left eye (i think), but when using scopes i use my right eye. I do a lot of binocular astronomy and have never had a problem.

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That's nice ?  I have considerable astigmatism in both eyes - observing is not comfortable so I image.

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5 hours ago, beka said:

Hi Sedna,

As Uranus is near the limit of naked eye visibility and since there are many factors including atmospheric seeing that can affect  our ability to see down this limit, I don't think you should be all that disappointed. If your vision is 20/20 then there is not much chance any kind of glasses will help.

Best

Thanks Beka. I guess I should have specified that, in my case, I know I had 20/20 vision for a long time, but it might have gotten worse recently. Also, Death Valley has a very dry, clear sky, so it's hard for me to blame it on atmospheric conditions. I guess I just need to get my eyes checked for peace of mind ?

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1 hour ago, LukeSkywatcher said:

I'm 44 yrs old. I wear glasses 24/7 for tv etc. I never wear them when observing. I just find them too uncomfortable and cant get close enough to the EP. 

I have a teeny tiny astigmatism in my left eye (i think), but when using scopes i use my right eye. I do a lot of binocular astronomy and have never had a problem.

Thanks Luke. Do you just not wear them with the scope, or even for star gazing? My thinking is, with the telescope you can always adjust the focus for your eyes, but for just watching the sky, maybe I need glasses :(

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Depends on detail. Visual magnitudes are hard to determine anyway. With no glasses how many Pleiades stars can you count, how close together? Ditto for craters on the moon. Don't forget to blink as drying eyes give blurry vision.

M31 is a smudge, M13 a fuzz ball. 

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8 hours ago, 25585 said:

Depends on detail. Visual magnitudes are hard to determine anyway. With no glasses how many Pleiades stars can you count, how close together? Ditto for craters on the moon. Don't forget to blink as drying eyes give blurry vision.

M31 is a smudge, M13 a fuzz ball. 

I think I can only see M31 is averted vision. Is that bad?

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54 minutes ago, Sedna said:

I think I can only see M31 is averted vision. Is that bad?

I think that under skies that good you should be able to see M31 with direct vision. Under much worse skies (mag 20.5 SQM) I’ve seen M13 with averted vision which is smaller and harder. At that time I was seeing magnitude 5.5 stars. I’m assuming your site was mag 21.8 or maybe higher so magnitude 6+ stars should have been visible.

Don’t forget that full dark adaptation can take a long time to achieve. In my book, under the darkest skies I still think it improves anything up to an hour after last looking at a bright light, certainly 45  mins. I recall I’m the past still seeing the effects of having looked at a bright phone screen half an hour afterwards. So it is well worth making sure your screen is dimmed well, possibly using red film over it to keep your adaptation.

Another suggestion may be to use binoculars too, to help locate it and then immediately try afterwards with the naked eye.

One other possibility is that perhaps your eyes are not so sensitive in the blue end of the spectrum, making it harder to see?

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47 minutes ago, Stu said:

I think that under skies that good you should be able to see M31 with direct vision. Under much worse skies (mag 20.5 SQM) I’ve seen M13 with averted vision which is smaller and harder. At that time I was seeing magnitude 5.5 stars. I’m assuming your site was mag 21.8 or maybe higher so magnitude 6+ stars should have been visible.

Don’t forget that full dark adaptation can take a long time to achieve. In my book, under the darkest skies I still think it improves anything up to an hour after last looking at a bright light, certainly 45  mins. I recall I’m the past still seeing the effects of having looked at a bright phone screen half an hour afterwards. So it is well worth making sure your screen is dimmed well, possibly using red film over it to keep your adaptation.

Another suggestion may be to use binoculars too, to help locate it and then immediately try afterwards with the naked eye.

One other possibility is that perhaps your eyes are not so sensitive in the blue end of the spectrum, making it harder to see?

Hi Stu, thanks for the input. Yes, I think I need to go back to Death Valley this winter and really discipline myself not to check the star app before I can conclude that my precious 20/20 vision is gone. According to lightpollutionmap.info, my site was exactly mag 22 SQM (no moon and clear, dry sky).

That's an interesting suggestion that my rods could be sensitive to a longer wavelength than most people. I doubt it, but maybe there are common variants that shift rod sensitivity towards red. I'm actually a neuroscience grad student, so you've given me an interesting new topic to read up on :)

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2 hours ago, Sedna said:

Hi Stu, thanks for the input. Yes, I think I need to go back to Death Valley this winter and really discipline myself not to check the star app before I can conclude that my precious 20/20 vision is gone. According to lightpollutionmap.info, my site was exactly mag 22 SQM (no moon and clear, dry sky).

That's an interesting suggestion that my rods could be sensitive to a longer wavelength than most people. I doubt it, but maybe there are common variants that shift rod sensitivity towards red. I'm actually a neuroscience grad student, so you've given me an interesting new topic to read up on :)

Sounds like you are ideally placed to find out! I genuinely have no idea if that is a possibility but it seems worth investigating.

Best way to check is probably to go back and do some limiting magnitude checks on stars and then on Uranus. I’ve seen it in binoculars from very poor skies (<mag 19), it is tricky but doable, so I it must be possible with the best skies.

Let us know how you get on.

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On 28/06/2018 at 23:01, Sedna said:

2) I was checking the star chart app fairly frequency to orient myself. Maybe my vision never fully adjusted? I think I must have gone at least 20 minutes without looking, which should be enough to fully adjust?

I think this might be your problem.

Looking at a computer / tablet / phone screen for the briefest time will almost completely wipe out any dark adaptation you might have. Even if the app has a 'night' setting that turns things red, this is the case. I hate night settings, they simply don't work, and lead to false expectations by unwary users. If you really need to use a screen, you need to filter it by placing a red gel over it. The best stuff (the only one I will use) is called rubylith. You can buy it in sheets.

Dark adaptation is a complicated process. 20 - 30 minutes of complete dark should see most of the adaptation done, but your night vision improves for many hours, albeit at a reduced rate.

Another mistake often made by beginners is the use of red lights. There is a myth that a red light won't damage your night vision. To an extent this is true, as the eye is less sensitive to the red end of the spectrum than it is to the blue, but the overriding factor is the *brightness* of the light. A very dim white light is much better than a bright red light. A very dim red light is best.

Try shielding your device properly and go back to the dark sky site. It will make an enormous difference!

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2 hours ago, Stu said:

Sounds like you are ideally placed to find out! I genuinely have no idea if that is a possibility but it seems worth investigating.

Best way to check is probably to go back and do some limiting magnitude checks on stars and then on Uranus. I’ve seen it in binoculars from very poor skies (<mag 19), it is tricky but doable, so I it must be possible with the best skies.

Let us know how you get on.

Thanks! Will do.

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19 minutes ago, DeepSkyBagger said:

I think this might be your problem.

Looking at a computer / tablet / phone screen for the briefest time will almost completely wipe out any dark adaptation you might have. Even if the app has a 'night' setting that turns things red, this is the case. I hate night settings, they simply don't work, and lead to false expectations by unwary users. If you really need to use a screen, you need to filter it by placing a red gel over it. The best stuff (the only one I will use) is called rubylith. You can buy it in sheets.

Dark adaptation is a complicated process. 20 - 30 minutes of complete dark should see most of the adaptation done, but your night vision improves for many hours, albeit at a reduced rate.

Another mistake often made by beginners is the use of red lights. There is a myth that a red light won't damage your night vision. To an extent this is true, as the eye is less sensitive to the red end of the spectrum than it is to the blue, but the overriding factor is the *brightness* of the light. A very dim white light is much better than a bright red light. A very dim red light is best.

Try shielding your device properly and go back to the dark sky site. It will make an enormous difference!

Thanks for the feedback, I'll look into rubylith. Probably I also need to become less dependent on apps and just learn the sky ;) though I seriously doubt I would ever find Uranus in the scope without a detailed chart of all the nearby stars.

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7 hours ago, Sedna said:

I think I can only see M31 is averted vision

Given your 20/20 vision, M 31, the Andromeda  galaxy, should be a very easy, eye-catching view with direct vision at your Bortle 1 site, after a few minutes of adapting your eyes to the darkness. You mentioned the possibility of a mild myopia due to your computer screen work. This might be accentuated by the so-called "night myopia", which can worsen your suspected mild myopia up to -2 dpt (in a German study with 2300 probands, 14% of probands -0,5 dpt, 11% from -0.5 to -2 dpt !). This could e.g. cause some problems, when driving at night (sharpness of letters on traffic signs as an indicator).

I'd suggest that you let your eyes check again by your optometrist, if possible, at a very low light intensity. If you have a good relation to your optometrist, he might perhaps even lend you the old-fashioned eye-glasses frame with some appropriate glasses to try out under the stars. Or you might order some cheap glasses from an online shop, just to try.

Hth.

Stephan

Edited by Nyctimene
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20 hours ago, Sedna said:

Thanks Luke. Do you just not wear them with the scope, or even for star gazing? My thinking is, with the telescope you can always adjust the focus for your eyes, but for just watching the sky, maybe I need glasses :(

If I'm just using my eye to look up, I wear them. If using scope or bins, I don't. My optician said my astigmatism is so slight that she almost didn't detect it. Without my glasses though, my eyesight is not great, but far from bad. 

Edited by LukeSkywatcher

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Memorising asterisms, familiar patches and handspan distances to objects, as if the sky was an atlas is good for approximations. Use a Telrad as a hand held aid like an orienteering compass. Digital setting circles are guides not drives.

For atlases use rear lit red. I use the black sky version of Sky Atlas 2000. Red shone onto it or through it only light up the white symbols. Glow in the dark planispheres and maps can be good general guides.

 

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I never know how many degrees up something is. A good guide, is a clenched fist at arms length (at ground level) = 10 degrees. 

"Memorising asterisms"

Forget the name they have. Think of what they look like to you. I call the Seven Sisters (M45), the shopping trolley. 

Edited by LukeSkywatcher
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2 hours ago, LukeSkywatcher said:

I never know how many degrees up something is. A good guide, is a clenched fist at arms length (at ground level) = 10 degrees. 

"Memorising asterisms"

Forget the name they have. Think of what they look like to you. I call the Seven Sisters (M45), the shopping trolley. 

Thanks--yeah, I know all the basics ones. I just have trouble with really dim patches of sky, like if I'm looking for Uranus in Pisces, then it's tempting to consult an app because the stars are so dim :(

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7 hours ago, Nyctimene said:

Given your 20/20 vision, M 31, the Andromeda  galaxy, should be a very easy, eye-catching view with direct vision at your Bortle 1 site, after a few minutes of adapting your eyes to the darkness. You mentioned the possibility of a mild myopia due to your computer screen work. This might be accentuated by the so-called "night myopia", which can worsen your suspected mild myopia up to -2 dpt (in a German study with 2300 probands, 14% of probands -0,5 dpt, 11% from -0.5 to -2 dpt !). This could e.g. cause some problems, when driving at night (sharpness of letters on traffic signs as an indicator).

I'd suggest that you let your eyes check again by your optometrist, if possible, at a very low light intensity. If you have a good relation to your optometrist, he might perhaps even lend you the old-fashioned eye-glasses frame with some appropriate glasses to try out under the stars. Or you might order some cheap glasses from an online shop, just to try.

Hth.

Stephan

Hi Stephan, good suggestion. Yeah, I'm also thinking M31 should've been easy from that sky (Bortle 1). With my direct vision, I think I could kinda see it, but it was so dim I had to almost wonder if I was imagining it.

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Sometimes the sky can be too good. At home in Amsterdam I am spoiled by a simple sky that just shows the brightest twenty stars, but if I get away to a dark site the view is spoiled and confused by thousands of faint stars. It can be hard to pick out familiar constellations if the sky is too dark. Maybe that "problem" is part of the reason you couldn't pick out Uranus or M31 with the naked eye.

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4 hours ago, Ags said:

Sometimes the sky can be too good. At home in Amsterdam I am spoiled by a simple sky that just shows the brightest twenty stars, but if I get away to a dark site the view is spoiled and confused by thousands of faint stars. It can be hard to pick out familiar constellations if the sky is too dark. Maybe that "problem" is part of the reason you couldn't pick out Uranus or M31 with the naked eye.

Hi Ags, I definitely have experienced that before. In this case though, I found Uranus with the telescope and thus knew exactly where to look ... but upon looking, I still didn't see it. Like I say, even some of the main stars in Pisces were really only visible to me with averted vision ?.

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