The Bench

Most of us don’t do a whole bunch of night sailing, except for the occasional distance race or when trying to make good distance on a cruise. Sailing at night opens up a whole bunch of new issues, and since we don’t get much practice doing, the solutions aren’t always obvious.

One tremendous issue is the visibility (of lack thereof). People rarely realize how dependent they are on sight as the primary sense until it is taken away by darkness. We key so much of our world to sight, and being deprived of that sense interferes with our ability to operate normally. It’s at best annoying, and at worst, terrifying.

Being able to see your instruments helps alleviate some of that terror. You can at least be reassured by the same numbers that you see while sailing during the day, and compare your situation against that. Any aircraft pilot will tell you that no matter what you think you feel while flying, the instruments rarely lie. Your body might tell you that you’re in a slow ascent, but the instruments will tell you for certain if that’s true. Basing your decision off a gut feeling while flying can easily get you killed.

For instruments to be visible in the dark, some sort of lighting is required. On old analog type displays, there was often a dimable incandescent bulb inside the unit that provided a nice dull glow. Some analog instruments also had luminescent paint to augment the visibility. Most digital instruments (ours included) use LEDs for back lighting.

The problem with instrument back lighting is that your eyes adapt to the dark, but the lighting level typically doesn’t change unless you control it. Human eyes reach one plateau of dark adaptation around 9 minutes, and another hours later. Instrument lighting levels at one point in the cycle may be completely wrong for a later point. Fortunately, it is possible to control the system lighting level (see "Set Light Level") and the lighting level for individual disaplays (see "Remote displays commands: @Jn" section) on the Ockam system. Note that the system light level will control the maximum brightness of all the displays, while the individual display control can dim individual displays down from the system maximum.

Another problem is wavelength perception. The human vision sytem perceives some wavelengths of light as brighter than others. Two light sources of identical physical luminosity but different wavelengths are perceived as having different brightnesses. Pure red light appears to be dimmer than other colors, but that’s not the reason that most night lighting is red. Most night lighting is red because that’s what was used in photography dark rooms (remember those?). Red light was used in dark rooms because black and white film had poor response in the red part of the spectrum, so being exposed to red light would not ruin developing photographs like other colors of light. Red lighting for night use came into common use during World War 2, but the reasoning behind it was not well understood - they just did it that way because it worked in the dark room. It was serendipity that the human eye didn’t change dark adaptation as quickly when exposed to red light.

All displays on the Ockam system now use red back lighting. Some of the older Matryx displays have a green backlight. The Matryx displays with green backlights can be converted to red back lighting if desired however. The green back light shouldn’t interfere too badly with night vision, as the Matryx displays can be individually dimmed lower than the system lighting level.

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Hi everyone! It’s a busy time of year for the marine industry in the northern hemisphere. All the boats are coming out of their winter hibernation, and all the regattas are running. Things are heating up here, as evidenced by our shipping activity and our web statistics.

Speaking of web statistics, I couldn’t help but notice that we had 13 hits from an Amiga computer! If whoever used that computer to look at our web site drops me a line at dan@ockam.com, I’ll try to send you a little goody in the mail.

I’m working on a few ideas for blog entries (high update GPS units, ultrasonic wind sensors), but if anyone has any particular subject they would like to read more about, drop me a line.

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Many people are familiar with weather reports through a variety of media. We all supplement our day-to-day weather awareness with forecasts from the newspaper and TV news. The Internet has become a very popular way to get sailing weather, as it delivers the right information at the right time. And as always, The Weather Channel and NOAA Weather Radio are big favorites with sailors. But how many people get weather information through the phone? Not many, I would venture. However, this is a fast and easy way to raise your weather awareness while out on the water, simply using any cell phone. While you can frequently get detailed weather data using wireless web browsing, it’s not always available due to limited time, limited hardware, or poor signal strength. The information here applies to the United States, although many other countries have similar systems in place for public weather information.

One way of obtaining current weather information is through the FAA/NWS METAR network. Almost every airport in the United States has an automated weather station now (called either ASOS or AWOS). Every airport that has an automated station also has a voice line to call for automated weather information. In highly populated areas, such as Long Island Sound, there are many airports near the usual sailing areas, so it’s easy to get a good mental picture of the weather conditions over a wide area. You may be able to see things like the sea breeze filling in, or an expected wind change starting to work through the area. There are a few important limitations to note when using the METAR reports. First, the observations are only reported once an hour some time in the ten minutes preceding the top of the hour. Second, airports are infrequently sited directly on the water, so there is typically some difference from the airport observations and conditions on the water. Third, these observations are from automated weather stations that are following reporting algorithms created for aviation, so they may not tell you exactly what you’re accustomed to hearing.

Another method of getting weather information by telephone is through the NOAA National Data Buoy Center Dial-A-Buoy program. This automated information line gives you the current conditions from the network of oceanographic data buoys maintained by NOAA NDBC. It can also provide the current NWS marine forecast for that location. Location is selected by one of two methods: you either need to know the buoy ID, or the approximate latitude and longitude in degrees and minutes. The buoy ID number can be found by clicking on the map on the front page of the NOAA NDBC; there are instructions on the Dial-A-Buoy page to enter buoy IDs with letters. It may be handy to have a small list of local buoys when calling the Dial-A-Buoy line. Otherwise, entering the lat/lon may not give you the buoy you wanted. The major drawback to getting data from the NDBC is the poor spatial resolution. There are not many data buoys out there, so the one closest to you may be some distance away. However, they are frequently located away from land, so you will see less of any land effect than if you check the airports. You also get sea state information from many of the buoys.

A third method of getting information is through the PORTS network. The PORTS network is limited to only 15 areas right now, but these areas also happen to have a lot of sailing activity. Some areas only have a few stations, but most have several. The availability of information varies by PORTS station; the web site details what is reported from each station. In addition to meteorological data, water data is also reported for most stations.

This list is by no means comprehensive. There are many automated information systems available for call-in access. The outlets listed here are a good start, and cover a large area of the United States. While checking out the web links here, click around to see what other weather and oceanographic resources are provided by the US government - maybe you can find something interesting!

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