Why a red screen filter protects your night vision
Your eyes need 20 to 30 minutes in darkness to reach most of their night sensitivity, and one glance at a white laptop screen can set that back. The rods that do the work in the dark respond very little to deep red light, which is why observatories and darkrooms are lit red. A red screen filter brings the same idea to a Windows display.
Night Vision Color Filter lays a red layer over every monitor, taskbar included, and covers a screen you connect later without a restart. The layer is click-through and never takes focus, so star-charting software, capture programs and telescope control panels work underneath it exactly as before.
The usual complaint about software red modes is that the screen ends up bright red instead of dim red. That is why this one has a separate darkening control as well as the tint.
How to make your screen red and dim on Windows
For the darkest result in the field, combine Maximum and some darkening with your laptop's lowest backlight setting. The filter can only darken the picture; the backlight behind it is still yours to turn down.
- Click the filter's notification-area icon to open the tray panel.
- Pick a level. Medium suits a dim room; Maximum is for a dark site once your eyes have adjusted.
- In Settings, use Strength for a level between the presets, and Darken as well to cut brightness while keeping the red.
- If the shortcut clashes with software you run at the telescope, set your own key under Turn it on and off.
Choosing a shade of red light for night vision
There is a trade-off between darkness and legibility. The deep maroon at the dark end of Which red sends the least light into your eyes and is the one to use during an observing session. The warmer orange-reds at the other end make small text, chart symbols and colored markers easier to tell apart, which helps when you are reading a planning list or captioning images in a dim room rather than looking through an eyepiece.
If you already use a red headlamp or flashlight, Browse lets you pick a color close to it, so your eyes see one red all night instead of two.
A red light filter for an astronomy laptop
A field laptop is usually opened in the dark, which is exactly when a white sign-in screen hurts most. With Start with Windows on, the filter comes up as soon as you sign in, with the level and shade you used last.
Set Turn it off after before a session and the screen returns to normal on its own once you pack up, so the next person to use the PC in daylight does not meet a red desktop.
