What Is Dark Vision When Using a Telescope?

If you’ve ever done anything requiring you to see in the dark, you’ve used dark vision without realizing it. If you’re an amateur astronomer or just enjoy using a backyard telescope, you need dark vision to do your best work. What is dark vision when using a telescope and how do you get it?

What Is Dark Vision?

If you’re not familiar with the term, “dark vision” might sound like some kind of instrument to you, especially when referring to using it with a telescope.

Fortunately, that’s not the case. Dark vision is the ability to see well without a light source. Some people have better dark vision than others, but much of that depends on how often you use dark vision, and what you use it for. The process of your eyes coming fully night vision adapted takes around 45 minutes.

The Physical Aspects of Dark Vision

As your eyes adjust to low light conditions, your pupils dilate, allowing more light into your eyes. That takes only a few seconds.

There’s more to dark vision than pupil dilation. Once your pupils fully dilate, two chemicals that don’t work in the light begin to work on the rods and cones in your retinas, making them more sensitive to light.

Your cones reach full sensitivity within 10 minutes, but it takes your rods another 20 minutes or so to get to their maximum sensitivity.

This chemical process is why suddenly flipping on a bright light after you’ve been asleep in the dark for several hours is so painful. Yes, your pupils can contract quickly, but reducing your rods’ and cones’ sensitivity takes more time.

Who Uses Dark Vision?

Anyone who needs to be able to see clearly in the dark uses dark vision. Military units involved in night operations use it. Pilots need dark vision, even with their instruments. It’s an essential part of astronomy and astrophysics, too. And, of course, amateur astronomers use it.

To put it another way, people who use dark vision do so because they do something that requires them to see as clearly as possible in the dark.

Where You Get Your Best Dark Vision

When talking about dark vision when using a telescope, your eyes only adjust to the level of darkness in which you set up. If you’re a backyard astronomer near a city, your visual acuity in the dark won’t be as sharp as that of a backyard astronomer living on a farm in the sticks.

You get your best dark vision when you’re away from all light sources, including light pollution from cities and towns. Depending on what you want to do with your telescope, your preferred degree of dark vision may vary.

Dark Vision with a Telescope

You don’t have to be an astronomer to know that you can see more and fainter stars when you’re away from light, and also when your eyes have adjusted to the dark.

When using a telescope, dark vision simply involves allowing your eyes to adjust to the darkness in the sky so you can see faint objects through your telescope’s viewfinder. Once your eyes have fully adapted to the dark, you can see far more.

How Do I Get Dark Vision?

The best way is to find a place where there’s as little light as possible. When using dark vision with a telescope, that can mean heading out into the country if you live near a city or any source of light pollution.

Once you’re out, take roughly 45 minutes to let your eyes adjust to the darkness. Then stay in the dark for as long as possible. Avoid going back towards light sources until you’re calling it a night.

Ways to Maintain It

The best way to maintain your dark vision is to stay in the dark. However, you might need light to set up your telescope, read star charts, and take notes. What now?

This is where a red flashlight comes in. Red light doesn’t affect your night vision the way other colors of light do. You can buy a red LED flashlight or use a red covering over a regular flashlight, like red cellophane or a lens cover.

Avoid using your cell phone for anything unless you’re only using apps designed for use in the dark. Make sure you’ve got all your notifications turned off and your phone in do-not-disturb mode. The last thing you want is a Facebook notification or a text message appearing on your screen and disrupting your vision.

Your best bet is to avoid using your cell phone at all, but some apps work quite well for amateur astronomers. So stick to those if you must use your phone.

One good idea for developing the best dark vision possible is to avoid sunlight and bright lights during the day before you go out. You don’t have to turn into a hermit, but you’ll get better dark vision to use with your telescope if you do this before you head out.

Ways to Lose It

Going back into the light will destroy your dark vision very quickly. Even just popping inside to use the bathroom or grab a snack will do it. If you’re in your own yard, turn off every light in your house and keep them off. Avoid opening your refrigerator because of the light inside, too.

If you’re going out to the country, bring snacks with you, use the bathroom before you go, or bring a sanitary way to do your business to avoid leaving anything behind.

Final Thoughts

Dark vision when using a telescope is merely letting your eyes fully adjust to the darkness to see more through your telescope. It takes more than letting your pupils dilate, though, so you need to give yourself a full 30 to 45 minutes to allow your eyes to adjust fully.

Your dark vision allows you to see faint objects in the sky, either with the naked eye or with your telescope. Because of that, you should always let your eyes adapt to darkness completely, and have ways to maintain your dark vision for as long as you need.