It's hazardous to stare at the sun with your naked eye and to look at it with a telescope is far worse. Both can result in a big blind spot in the middle of your eye. Your eye has a lens in it which focuses the sun on the back of your eye. And your telescope has a sequence of lenses that do the same.
There is no sensation of pain at all as you have no pain receptors at the back of your eye.
But later on you may find you can't see as you used to, and then - in some cases it eventually recovers but in other cases it is permanent.
Every solar eclipse, then hospitals get patients report with eye injuries from people who have just stared too long at the sun with their naked eye.
Sir Isaac Newton is a famous example of an astronomer who developed temporary partial blindness for several months as a result of looking at the sun through a telescope, and may have been permanently affected slightly. Discussion here: Eye problems of other early solar observers
Don't look at the sun through a telescope or binoculars at all.
It's actually the UV light that is most damaging apparently, not the infra red (though as you see from that telescope video, with a good telescope the infra red is very dangerous also).
And when there are clouds, they may not block UV light, so it is also not safe to stare at the sun even with your naked eye when it is behind clouds.
At sunrise and sunset people often do look at the sun when it is close to the horizon and rather dim, often behind clouds - has to go through a lot of atmosphere.
You won't come to any harm from it just naked eye viewing of the sun during a glorious sunset - especially as we don't stare at the sun but your eye keeps moving around and it is usually behind clouds.
But even then - it's not recommended to just stare at even a rising or setting sun for long.
Never safe to look at the sun through telescope or binoculars any time of day, even at sunrise and sunset.
Having said that, Galileo did look at the sun, only at sunrise and sunset without protection, and though he went blind, not thought to be due to this. But definitely not recommended, he was lucky and also very careful, also a very low power telescope compared with modern ones, later on he used projection methods. Galileo, solar observing, and eye safety
The only time it is totally safe to look at the sun with unprotected naked eye is during a total solar eclipse when only the corona is visible and the brighter stars.
You can't see the corona with a solar filter in place - so if you plan to watch it during an eclipse you remove the filter. And with naked eye - remove the specs.
But you have to be sure of the timing to look away or replace the filter before it exits from behind the disk of the Moon, before even the diamond ring phase. See Page on mreclipse.com
Never stare at it or look at it through binoculars or telescope during a partial eclipse, or if even a tiny part of it is showing.
Instead project from eyepiece onto a sheet of paper as in that video.
Or use a pinhole for a "pinhole camera" type projection anyone can do - or if you use solar filters - you must be sure they are rated for astronomical viewing of the sun - put them over the objective rather than the eyepiece end - and not use them if there is the slightest scratch.
View the Sun Safely - Sky & Telescope
For naked eye viewing you can use the "eclipse glasses" again so long as there are no scratches to let the light through.
You can also buy special solar telescopes if you are very keen on observing the sun.
Or simplest of all, just monitor the sun online through the SOHO website which keeps an eye on it 24/7. You often see comets passing near the sun which is rather cool.
Solar and Heliospheric Observatory Homepage
Here is where you can watch it in real time
The Very Latest SOHO Images
There is no sensation of pain at all as you have no pain receptors at the back of your eye.
But later on you may find you can't see as you used to, and then - in some cases it eventually recovers but in other cases it is permanent.
Every solar eclipse, then hospitals get patients report with eye injuries from people who have just stared too long at the sun with their naked eye.
Sir Isaac Newton is a famous example of an astronomer who developed temporary partial blindness for several months as a result of looking at the sun through a telescope, and may have been permanently affected slightly. Discussion here: Eye problems of other early solar observers
Don't look at the sun through a telescope or binoculars at all.
It's actually the UV light that is most damaging apparently, not the infra red (though as you see from that telescope video, with a good telescope the infra red is very dangerous also).
And when there are clouds, they may not block UV light, so it is also not safe to stare at the sun even with your naked eye when it is behind clouds.
At sunrise and sunset people often do look at the sun when it is close to the horizon and rather dim, often behind clouds - has to go through a lot of atmosphere.
You won't come to any harm from it just naked eye viewing of the sun during a glorious sunset - especially as we don't stare at the sun but your eye keeps moving around and it is usually behind clouds.
But even then - it's not recommended to just stare at even a rising or setting sun for long.
Never safe to look at the sun through telescope or binoculars any time of day, even at sunrise and sunset.
Having said that, Galileo did look at the sun, only at sunrise and sunset without protection, and though he went blind, not thought to be due to this. But definitely not recommended, he was lucky and also very careful, also a very low power telescope compared with modern ones, later on he used projection methods. Galileo, solar observing, and eye safety
The only time it is totally safe to look at the sun with unprotected naked eye is during a total solar eclipse when only the corona is visible and the brighter stars.
You can't see the corona with a solar filter in place - so if you plan to watch it during an eclipse you remove the filter. And with naked eye - remove the specs.
But you have to be sure of the timing to look away or replace the filter before it exits from behind the disk of the Moon, before even the diamond ring phase. See Page on mreclipse.com
Never stare at it or look at it through binoculars or telescope during a partial eclipse, or if even a tiny part of it is showing.
Instead project from eyepiece onto a sheet of paper as in that video.
Or use a pinhole for a "pinhole camera" type projection anyone can do - or if you use solar filters - you must be sure they are rated for astronomical viewing of the sun - put them over the objective rather than the eyepiece end - and not use them if there is the slightest scratch.
View the Sun Safely - Sky & Telescope
For naked eye viewing you can use the "eclipse glasses" again so long as there are no scratches to let the light through.
You can also buy special solar telescopes if you are very keen on observing the sun.
Or simplest of all, just monitor the sun online through the SOHO website which keeps an eye on it 24/7. You often see comets passing near the sun which is rather cool.
Solar and Heliospheric Observatory Homepage
Here is where you can watch it in real time
The Very Latest SOHO Images
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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