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Great Astronomy Watch? YES!

Several years ago I read an article on watches in Astronomy Magazine.  Ever since, I have lusted over a particular watch reviewed in that article: the YES watch (  There are actually several styles within the YES family of watches (the Zulu, Inca, Kundalini, etc.) but they all share a common trait: the ability to calculate sunrise, sunset, moonrise, moonset and many other astronomical times for any location around the world and display them on a unique 24 hour dial.  Unfortunately, a brand new YES watch is quite expensive (I have never spent more than $50 dollars on a watch before).  But recently I won an eBay auction and picked up a used Zulu model for less than half the price of a new one.  Is this watch everything the article made it out to be?  YES!

The first thing that jumped out at me was the unique 24 hour display (see diagram below).  Twelve o’clock midnight is located at the bottom of the dial while twelve o’clock noon is located at the top.  The analog hour hand shows your current time on this 24 hour display (there are no minute or second hands).  What is really amazing is the ingenious way that the watch displays astronomical data.  After you enter the date and your geographic location (there are 580+ cities worldwide pre-entered into the system, or you can manually enter latitude and longitude values), the watch calculates a variety of astronomical values (sunrise, sunset, etc.) and visually depicts them on the watch’s digital displays.  The central digital display uses sunrise and sunset values to visually depict the hours of day and night time.  An outer LCD ring uses moonrise and moonset values to visually depict when the moon will be above the horizon.  The moon phase is also shown on the bottom half of the display.  Digital time (and other common features like alarm settings, stopwatch, timer, etc.) is on the top half of the display.

You can preset two locations (“Home” and “Away”) into the watch and then quickly jump back and forth between the two.  This can be handy if you travel a lot and wish to note the time difference between locations.  Or, if you routinely use a remote computerized telescope in New Mexico, the Canary Islands, or in South America, you can set your “Away” location to that remote spot and quickly determine if the sun has set yet and if the moon will interfere with your observations for the evening.  Or simply set the location to someplace you are daydreaming of.  In the first photo below I’m displaying today’s information for Reno, NV.  In the second photo I’m displaying Sydney, Australia (where I suspect it is a bit warmer this time of year).

Reno, NV

Sydney, Australia

In addition to the standard features found on digital watches (alarm, stopwatch, timer), there a few features that will appeal to astronomy enthusiasts: the ability to calculate astronomical times for future dates, and a countdown feature.  Let’s say you want to know what the moon will be like on Christmas evening.  Go to the “SM-Calc” (Sun Moon Calculator) feature and enter “12/25/2012”.  The watch will briefly calculate the data, update the LCD visual displays, then cycle through the following information:

  • Day of Year (e.g., 360)
  • Lat/Long
  • Sunrise
  • Solar noon
  • Sunset
  • Percent moon illumination
  • Moonrise
  • Moonset
  • Date/time of next new moon
  • Date/time of next full moon

If you’re a skeptic of all the Mayan calendar end-of-the-world hoopla, then you’ll realize this is a very smart watch… after all, it successfully calculates there will be a sunset on Christmas morning!  If you think there is credence to the Mayan calendar hype (or just want to have fun), you can enter “12/21/2012” into the countdown feature and count the minutes until the end of the world!  Or, if you want to remind yourself of a true astronomical event (like an occultation or a particularly exciting display of the moons around Jupiter), simply enter the time of the event and it will count down and sound the alarm at the appropriate moment.  Hint: set the countdown timer for an hour before the event so that you have time to set up your telescope first.

If you look at the picture below, which shows the watch set to November 1st, you’ll notice that the daylight hours shift noticeably towards the afternoon hours.  Because the Earth travels around the Sun in an elliptical orbit, there are periods when the sun is at its highest point (solar noon) before 12:00 noon and other times it is at its highest after 12:00 noon.  You’ll notice this same effect if you use a sundial over the course of a year to create an analemma.  This difference between apparent solar time and mean solar time (also known as the “equation of time”) is visually depicted on the watch by the daylight hours shifting in one direction or another.  You can take advantage of this phenomena and turn the watch into a rudimentary compass.  If you rotate the outer bezel so that the sunrise and sunset lines are evenly spaced between sunrise and sunset depicted on the LCD, the yellow “sun stone” at the top of the bezel will depict solar noon.  Or you can just use the solar noon time calculated by the watch (using the procedures in the paragraph above) to set the bezel… on November 1st solar noon was at 12:43pm.  If you rotate the watch until the hour hand points towards the sun, the sun stone will point south and the moon stone will point north (a helpful feature if you’re trying a rough polar alignment during the day).

The YES watch goes on sale a couple times a year (e.g., they have a Christmas sale on right now).  As I mentioned earlier, one can manage to get a deal on a used watch on eBay.  If you wish to try the eBay route, here are a couple of tips:

  • You can save a search on eBay and have it email you anytime an item that meets your search criteria becomes available.  I saved a search for “Yes Zulu” and had approximately 2-3 email notices per year.
  • Do not bid too early.  This simply provides time for the price to be bid higher.  Set an alarm on your computer to notify you an hour or two before the auction ends, then place your bid.  You are hoping that other potential bidders have forgotten about the item or are not monitoring it closely.
  • If you bid for products on eBay, you can enter your maximum bid and the site will automatically increment your bid (up to your maximum authorized amount) if someone else becomes the high bidder.  This can be a handy feature if you do not wish to continuously monitor the bidding process (and can still make you the high bidder if someone else makes a last minute bid).
Category: Other Members