We had just departed the dock in the pre-dawn and were idling out through a narrow inlet in the dark, but the bright glow of my electronic instruments proved so blinding that I could scarcely make out the shoreline on each side of the cut. I laid a towel over the dash, and eventually my night vision kicked in.
That was a number of years ago, and at the time, using a towel to cover the tachometer, fuel monitor and other gauges at night was common practice. When you needed to check things such as the rpm, speed or fuel flow, you just lifted the towel for a quick look-see. Either that, or you turned off the instruments altogether, then switched them back on for a quick check. Primitive, yes, yet these were the only options that many helmsmen had at their disposal.
Illumination is a tricky thing. You need to read your displays, but too much light greatly affects your ability to see well in the dark. It takes about 30 to 45 minutes for your eyes to fully acclimate to darkness in the absence of bright illumination, but the process starts over each time lights are turned up. Your pupils again need to widen, and your eyes’ rods — specialized cells in your retinas that provide most of what we call night vision — must re-sensitize.
So it’s important to keep your electronic instruments and other lighting dimmed when you’re heading out on a trip in the wee hours, fishing at night, or returning to port in the evening. On the other hand, for optimal viewing during the day, the display brightness needs to be turned up, usually to 100 percent.
Today, thankfully, there are a number of ways to adjust the lights of your marine electronics and other instruments, short of covering them with a towel.
Dial It Down
Twelve-volt dimmer switches for marine applications are available in a variety of models. These devices are designed primarily for engine gauges, allowing you to adjust the lighting for the entire instrument cluster at once.
One of the easiest to install and simplest to use is the dial-operated Cole Hersee dimmer control, which requires a 3⁄8-inch hole to install. The Cole Hersee dimmer is light and compact, but the stem is a bit short (it might not fit thicker helm panels), and it is not totally waterproof. It operates with incandescent lights only, so it’s not compatible with LED lighting.
Blue Water LED’s dimmer control does work with LED lighting. Like the Cole Hersee dimmer, it requires a 3⁄8 -inch hole and utilizes a dial to adjust panel lights over a wide range of illumination levels. The Blue Water LED model also serves as the on/off switch for instrument lights.
Blue Sea Systems offers a highly versatile dimmer control. The Deckhand dimmer digitally adjusts LED, incandescent and halogen lights. It uses a black-box module and a Carling-style rocker switch, so on boats that utilize rocker switches to activate various accessories, the Deckhand dimmer is easily added to the existing switch panel. Once the device has been installed, you simply press down on the rocker to dim the lights or press up to increase illumination.
Touch and Go
The touchscreen displays from major marine-electronics brands — including Furuno, Garmin, Lowrance, Simrad and Raymarine — offer the ability to adjust the backlighting to match the time of day or night. The method of adjustment varies from model to model, but on many, a quick press of the on/off button lets you access an on-screen control to decrease or increase illumination at the touch or slide of your finger.
On trips where I leave before dawn, I usually start with the brightness turned down almost completely, but I find it helps to turn up the backlighting gradually as ambient light increases, allowing me to continue to see the display without suddenly destroying my night vision before daylight.
As that soft gray light of the morning creeps across the water, I like to increase illumination to around 15 to 25 percent. Just before sunrise, 50 percent illumination is about right, and once the sun is up, I increase the brightness to as much as 75 to 100 percent.
On models such as the Lowrance HDS Gen3 displays, a press of the on/off button (with the brightness menu open) ramps up the backlighting 100 percent; a second press dims the illumination to its previous level. This is especially helpful whenever you need to turn down the brightness quickly, such as when a thick fog bank suddenly reduces ambient light.
Many fishing boats today have multiple displays at the helm, often of the same brand. When these are interconnected via an NMEA 2000 network, a brightness adjustment on one affects all displays. This is a great convenience, as it eliminates the need to adjust each display individually.
Many electronic displays also offer a feature called “night mode,” which essentially changes the color palette to a red display against a black background. The rationale here is that the darker background keeps illumination levels to a minimum, and red doesn’t desensitize the rods in your eyes as much as other colors do, according to scientific studies. Thus night mode allows effective viewing and minimizes disruption of your night vision.
Red is also one of the least visible colors in the dark, at least to humans (making it a less-than-optimal choice for the port navigation light on boats), and for that reason, some boating anglers dislike using it, as making out objects on radar or reading data often becomes difficult. Instead, many captains choose to turn down the brightness on the normal display.
Whatever means you use to adjust instrument lighting, be thankful for the sophistication and ease of modern options. Today’s brightness-control systems are a great improvement over using a towel, and they help make nighttime on the water safer.
Dimmer Model: Deckhand Dimmer
Switch Style: Rocker
Type of Lights: Halogen, incandescent, LED
Dimmer Model: Dimmer Contro
Switch Style: Dial
Type of Lights: Incandescent, LED
Dimmer Model: Dimmer Control
Switch Style: Dial
Type of Lights: Incandescent