The best nights for sky viewing are dark and clear. With dark-adapted eyes you’ll get the best views. A regular light can ruin that night vision. One solution is to use a special flashlight designed for stargazing, or you can simply adapt a regular torch…
Give yourself at least 20 minutes if you want better night vision, but the longer the better. It can take several hours for your eyes to become fully adapted to the dark and reach optimal low light sensitivity, according to physicist, Dr Christopher Baird.
The problem with regular flashlights or Torches
Regular flashlights emit white light, which disrupts the advance of night vision. It emits too much in the blue and green spectrum. With the brightness, your pupil shrink and this reduces the amount of light entering your eyes.
The Solution: Red light flashlights (AKA Torches)
At night we see more clearly once our eyes are adapted (takes about 20 min) and red light helps with maintaining that night vision than that emitted by the normal bright flashlights.
- Bright light switches off the rhodopsin for night vision.
Why use red light for astronomy?
You’ll more likely get to observe faint night-sky objects. You’ll get better views.
Red light does not disrupt the forming of rhodopsin, a chemical released by the body when our eyes detect low light for roughly 20 minutes. This chemical aids our night vision and evolved to help us detect threats at night.
Submariners and other professions having to go from well lit premises to the outdoors are familiar with how red light preserves night vision.
Imagine yourself observing the sky at night and wanting to read a sky chart, check your device, or look up instructions — you’ll need lighting to see these clearly.
Especially, if you are just starting to learn the ropes of how to use your new telescope. Or if you have those extra eyepieces you’re yet to use. Red light is what you need.
As Jim O’Connor of the Tucson Amateur Astronomy Association explains: “It only takes a few seconds of bright light to cause the rhodopsin to decay…” and this is why astronomers use red flashlights when setting up, re-configuring, or refering to planispheres.
Red light torch app
You can use a red flashlight app, if you don’t have a flashlight that’s red. This is one way to improvise. For Apple, check out NightVision Light at the App Store and for Android, Red Telescope Flashlight at Google Play.
DIY red flashlight
How do you make a red light in astronomy? Here’s how to make a red light torch by simply adapting a conventional flashlight:
- Get some red cellophane and cover the front of the torch or flashlight with layers of the cellophane and then secure these layers with a rubber band. Trim the excess red cellophane and there you have it.
It’s as easy as that. You can get red cellophane online at Amazon.
- Or you can fit red gel light filter pieces over the lens. Art supply stores stock these, but they are also available at Amazon (click on image below to see details and price).
Where to buy red light torch
You can buy red light torches or flashlights online at Amazon and at astronomy speciality shops or techno gear shops. Here are a couple to consider…
Rechargable red light torch
A rechargable flashlight is handy. This one has a USB so you can charge it in your vehicle or using a solar charger or battery bank. It’s also waterproof.
Rechargeable red flashlight
available at Amazon
Lightweight small red light torch
For a flashlight you can stick in your pocket or clip on your belt or carry bag, you can’t go past this lightweight LED model…
Single Mode Red LED Torch Zoomable
Available at Amazon
If you want to free your hands, you can use a red headlamp. The problem with these is that they can get annoying when you are trying to look through the eyepiece of the telescope.
Bottom line
Important accessories for astronomers are observers’ flashlights that shine a very pure red light.
Every backyard astronomer should have a red flashlight in their kit. They are essential for navigating in those best dark places, reading a planisphere, and adjusting settings on the telescope.
The best ones are astronomy grade red flashlights. But, if you are just starting out, you could get away with an app on your phone or by making your own — For how to make a red flashlight for astronomy – scroll up.
