Having the correct time is important in all navigation, but is paramount for celestial. Determining longitude has always been the strictest test of timekeeping which is today improved by quartz clocks and worldwide broadcast time signals. These time signals are broadcast on shortwave frequencies of 2.5, 5, 10, 15, and 20 MHz in the USA, and a few others in the rest of the world.
In the past, there have been inexpensive radios whose crystal settings have been dedicated to receiving just these frequencies. These radios are no longer available, but digital tuning technology (like your car radio that can seek and scan) has made ordinary shortwave radios capable of receiving these signals reliably. The world band radios in this catalog are all suitable for this purpose.
As an alternative, one may phone the U.S. Naval Observatory at the following number, and hear a transcription of the time signals or visit our web site to view the time as a link from them.
For the time call: