The Deepstar bezel patent
Using the French Navy Deco table from that period, let’s pick a hypothetical depth for a first dive and the corresponding duration off the table, a dive to 39 meters which is (approx. 130ft) for 25 minutes. On the table, where the depth and time intersect, there are two sets of numbers. The primary number is the mandatory decompression time for this dive in minutes. The second number is the partial pressure of absorbed nitrogen in the body which is known as “Coefficient C”. This factor will be used later during a surface interval prior to a repetitive dive.
Now let us look at the Aquastar bezel itself. It has two scales, one inner scale and one outer scale. The inner scale is simply a traditional 60-minute elapsed dive time scale found on almost every other dive watch. The outer scale is the key to calculating repetitive dives, but more on that later….
Before jumping in, the diver will align the zero marker, or the lumed pip on the bezel to the minute hand to measure the duration of the dive, a regular procedure that is done to measure the time spent under water during the dive.
During the dive, the minute hand advances on the inner scale showing how many minutes have passed at the depth of 39 meters. Once the hand shows 25 minutes, previously determined and planned, the dive is over, and it is time to ascend to the decompression stop. A decompression stop should be made for 15 minutes after which the ascent to the surface should be completed.
Once at the surface, the outer scale can be used to factor nitrogen off-gassing in preparation for the second dive. Here’s where the previously determined “Coefficient C” of let’s say 1.6 is used. The 1.6 value on the outer scale of the bezel should now be aligned with the hour hand, that will advance, showing the values of decreased absorbed nitrogen (1.5, 1.4, 1.3, and 1.2). If the decreased value is above 1.4, the concentration of nitrogen in the body is too high, and a second dive cannot be made.
Now for the second dive. The second dive will be made to 30 meters since the second dive should be shallower than the first.
1st possible scenario: If we look at the outer P=55-12 meter scale and pick the 30 which is the dive depth planned, we’ll observe that the 6 minute mark on the inner scale aligns with the 30m mark on the outer bezel. This is important because this value is what will be used to determine the time “handicap/penalty” for the second dive. The penalty is the time to subtract from the dive time indicated by the table for the 2nd dive. This means, when enough time has passed, and the hour hand passes from the “Coefficient C” of 1.6, as previously determined from the tables in the first dive, down to a new “Coefficient C” of 1.1, 6 minutes will be subtracted from the dive time of the second dive planned on the dive table. Now, going back to the table, we find the 30 meter depth and then plan that dive for 30 minutes. Since this is a second dive, and the diver has stayed out of the water long enough for a new “Coefficient C” of 1.1, 6 will be subtracted from 30, giving an actual total of 24 minute dive time. Note: The decompression time stays the same in accord with the table, so a 3-minute mandatory decompression has to be made and according to the table the new “Coefficient C” is 1.5.
2nd possible scenario: If the surface interval wasn’t long enough to get into the 1.1 range, and let’s say the hour hand has reached only the 1.3 range, the number on the right, which is in this case “3” will be used as a multiplication factor to triple the 6 minute handicap/penalty, 6 x 3 = 18, then 18 minutes should be subtracted from the 30 minute dive time. The new time for the second dive would be for only 12 minutes. If the 1.2 range is reached, the 6 minute handicap would be doubled, then 12 minutes will be subtracted from the 30 minute dive time suggested by the table, giving an actual total dive time of 18 minutes for the second dive.
If enough surface interval time passes beyond the 1.1 range and passes into the “Normal” section of the scale, that is when we know that all nitrogen has off gassed from the body. At that point a second dive can be planned as a completely new (1st non-repetitive dive).
The Deepstar bezel was developed and patented based on scientific facts and researches conducted in the early 1960s about gas saturation in the human body while diving. Nevertheles, the above information is supplied for historical verification purposes only and is not intended for actual tpday’s use. Also the above repetitive dive scenarios and their calculations using those historical 1960s French Navy tables were replaced or updated since and are referred to here for historical verification purposes only.