How long to adjust eyes to the dark?

[Jojo204]

Hi all,

another pretty stupid question, but I’m quite excited today as I finally have a break in the clouds tonight and am going to do some visual observing (and try and spot the ISS). I want to know how long would it take my eyes to adjust to the dark and be able to see the stars fully? 

 

Thanks!

[des anderson]

Give yourself about 20/30 minutes and you should be fine, enjoy the views. Des

[Jojo204]

Just now, des anderson said:

Give yourself about 20/30 minutes and you should be fine, enjoy the views. Des

Thanks!

[PhotoGav]

As Des says, 20 to 30 minutes will give you fully dark adapted eyes, depending on age. The older you are, the slower the eyes proceed. Once you are fully dark adapted, do everything you can to preserve it as it can vanish in the click of a light switch and you are back to square one... Be extra careful of smartphones, which are very useful for planetarium apps etc, but have a nasty habit of glowing a very bright white when you aren't expecting it.

Good luck and have a great session!

[ZiHao]

10 minutes ago, PhotoGav said:

Be extra careful of smartphones, which are very useful for planetarium apps

Very true, even though you adjust the brightness to the minimum, the screen will still ruin your vision. Last year, was observing the Geminids from my balcony which has a bright orange streetlight very close to me so I have to use a t-shirt acting as a lightshield. In 15 minutes, my eyes could dark adapt pretty well ( 14yo, between bortle 7 and 8 skies ), got amazed by how many stars is visible in Orion in the zenith. And that's only possible when I am lying on the mat observing, otherwise, when star hopping through a telescope, screens and apps are a must hehe.

Happy viewing!

[Jojo204]

37 minutes ago, ZiHao said:

Very true, even though you adjust the brightness to the minimum, the screen will still ruin your vision. Last year, was observing the Geminids from my balcony which has a bright orange streetlight very close to me so I have to use a t-shirt acting as a lightshield. In 15 minutes, my eyes could dark adapt pretty well ( 14yo, between bortle 7 and 8 skies ), got amazed by how many stars is visible in Orion in the zenith. And that's only possible when I am lying on the mat observing, otherwise, when star hopping through a telescope, screens and apps are a must hehe.

Happy viewing!

I count myself lucky to live in a bortle 4 zone then!

[Stu]

I reckon under a really dark sky your eyes continue adjusting for anything up to 45 mins or an hour. With less good skies 20 or 30 mins will be enough. As has been said, it just takes an instant of looking at a bright light and you are back to square one again.

I do use an iPhone for viewing Skysafari, and find that even under fairly dark skies it is possible to use it without affecting my vision too much. There are options in the settings menu, accessibility sub menu I think which allow you to turn the display red for everything, even the home screen, plus reducing the white point down to a level which is hard to see unless very dark. This works for most situations, but if under really pristine skies I would probably still out a piece of red film over the screen to protect my vision.

The basic message is the longer the better, and protect it carefully once achieved!

[LukeSkywatcher]

20-30 mins sounds about right. 

[Jojo204]

5 hours ago, Stu said:

I reckon under a really dark sky your eyes continue adjusting for anything up to 45 mins or an hour. With less good skies 20 or 30 mins will be enough. As has been said, it just takes an instant of looking at a bright light and you are back to square one again.

I do use an iPhone for viewing Skysafari, and find that even under fairly dark skies it is possible to use it without affecting my vision too much. There are options in the settings menu, accessibility sub menu I think which allow you to turn the display red for everything, even the home screen, plus reducing the white point down to a level which is hard to see unless very dark. This works for most situations, but if under really pristine skies I would probably still out a piece of red film over the screen to protect my vision.

The basic message is the longer the better, and protect it carefully once achieved!

Well today I did and it took about 25 mins for them to be able to see constellations, satellites and the Milky Way was pretty obvious. I used Stellarium with lowest brightness and the red mode on and it didn’t mess up my vision much, but when I went inside once I was done I wanted to see how much one light effects me so I turned on a light then went back outside, I could barely see Vega for the first few seconds!

[JamesF]

Some people wear an eye patch over their "telescope eye" when using lights etc. so the dark adaptation is preserved.

I don't know how it affects others, but I have found it quite weird being outside in the dark with one dark-adapted eye and one that's used to bright light though.  I find it quite disorientating.  It feels as though my brain can't reconcile the two images when they're so different.

James

[Stu]

42 minutes ago, JamesF said:

Some people wear an eye patch over their "telescope eye" when using lights etc. so the dark adaptation is preserved.

I don't know how it affects others, but I have found it quite weird being outside in the dark with one dark-adapted eye and one that's used to bright light though.  I find it quite disorientating.  It feels as though my brain can't reconcile the two images when they're so different.

James

Yes, it is very weird!

[Charic]

I stopped using the patch for the same reason, one eye worked, the other didn't when you needed to move about??