Omega Seamaster Aqua Terra > 15,000 Gauss – The Most Antimagnetic Watch?

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After our primer on antimagnetic watches, and review of the IWC Ingenieur 500,000 A/m, the Rolex Milgauss, we come to perhaps the most recent of the trio – equipped with the latest technology – the Omega Seamaster Aqua Terra > 15,000 Gauss.

Omega Seamaster Aqua Terra > 15,000 Gauss

The Seamaster Aqua Terra >15,000 Gauss is affectionately known as the Bumblebee, named after its iconic black-and-yellow seconds hand. This watch was released back in 2013 and it marked the future of OMEGA movement technology. It was the first watch to house OMEGA’s Co-Axial calibre 8508 which is resistant to magnetic fields greater than 15,000 Gauss.

About the units

In horology the units used to measure magnetism can be quite confusing. Often we see terms like Gauss, A/m being used. In physics, two terms are defined. A magnetic field has both the H field and B field components, and they have different units. The A/m (amp/meter) is the SI unit of the H field strength and the Tesla is for the B field. Gauss is a unit for the B field and equivalent to 0.0001 Tesla.

Although the measure different things, an 80,000 A/m field is roughly equivalent to 1,000 gauss magnetic induction. And 15,000 Gauss is equivalent to 1.5 T and 1,193,663 A/m in vacuum. 1 Gauss = 0.0001 T and ~79.6 A/m.

So when the industry say antimagnetic on the caseback, it implies the ISO 764 which specifies that it is able to withstand a magnetic field of 4,800 A/m which is roughly 60 Gauss, without the magnetic field affecting the timekeeping capabilities. This is really the bare minimum, as almost all cases can afford this level of protection.

When this was released, OMEGA would gradually roll out the anti-magnetic movement technology to the rest of their watches over the years. Today’s OMEGA Master Chronometer watches undergo both METAS and COSC tests. METAS tests includes exposing the movements and cased watches to 15,000 Gauss and checking for their accuracy both before, during and after magnetism. We take a closer look at this watch as part of our survey of anti-magnetic technologies over the decades.

The case

This comes in a rather standard case size of 41.5mm and wears rather true to size. The case sides and top are vertically brushed, with a wide polished bevel that runs from lug to lug. The bezel is also mirror finished and the shape blends well into the case sides. The variant we photographed here is
the stock leather strap.

The bumblebee comes in both leather straps or steel bracelet. OMEGA also offers more than 50 NATO strap designs and materials to dress up (or down) the watch to your liking. Most would like this on a bracelet because of our tropical climate, but it wears great on either option. The dark brown leather straps are padded and thick to match the case and lug’s heft, and it felt sturdy and well made.

The dial and hands

Thanks to the lack of a soft iron shield, the watch is able to have a date window and a sapphire exhibition case back. The trapezium shape for the date window is a nice detail and matches the radial angles of the triangular markers.

Sharp and lume-filled hands and markers with matching trapezium date window.

The glossy stepped stripes on the dial play really well with light, and gives the otherwise plain dial some visual depth. The 5-minutes markers are also printed in contrasting yellow numerals, tucked along the circumference, providing good legibility without cluttering the dial. The
small bursts of yellow all-round also gives more symmetry to the layout. This movement was created before METAS, thus only have “Chronometer” printed instead “Master Chronometer” like the newer editions of Aqua Terra.

Crisp yellow printed markers and an extended bumblebee hand for extra legibility. Pinstripe dial texture is vaguely seen at the top left.

The signature black and yellow seconds hand probably commands the most attention at first look. This colour combination is designed to draw attention, like in warning labels and safety tapes. It’s a colour combination that few would disagree with. The alternating placement of colour on the
seconds hand also gave it its Bumblebee nickname. The black portions may camouflage in the black dial, but the yellow bits are cleverly positioned over the minute rail to maintain great legibility. The other hands and markers are in steel. The polished facets, wide hands and lume plots are typical of Aqua Terra designs.

The movement: Omega C.8508

This is powered by Calibre Omega 8508, likely the first non-magnetic (and not just anti-magnetic) movement by Omega. To mark this, the rotor is proudly engraved with >15,000 Gauss. Technologies in this movement have gone on to be almost a standard issue in recent movements such as the
Calibre Omega 8500 and 8900. The 8508 has two barrels to give an impressive power reserve of 60 hours.

While we had it, it was still going strong even after being undisturbed for almost 72 hours. Those familiar with Omega would know that these movements do not have quickset dates, instead it has a time zone function that changes the hour hand while maintaining timekeeping.

The highlight of this movement is definitely the use of silicon hairsprings. It applies the same anti-magnetism strategy to that in the IWC 3508 that we’ve reviewed earlier. But the execution in the OMEGA Caliber 3508 is much better with the use of silicon, over the niobium zirconium alloy as we discussed for IWC Cal 35790.

Concluding Thoughts

Though not a new release, the movement and design remains modern and relevant. The funky colour combination is neither dated nor gaudy. Current RRP is S$8,550 and $8,400 for the bracelet and leather strap variant respectively.

An immediate competitor to mind would be the Rolex Milgauss. The Bumblebee definitely provides a better value proposition and perhaps better technology than the Milgauss, though all bets are off, just because the latter is a Rolex.


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  1. In a recent article on Monochrome Watches Frank Geelen claimed that the Rolex Submariner was able to resist a magnetic field of 1000 Gauss. He also went further claiming that all mechanical watch movements were made to an industry standard to resist magnetic fields of 1000 Gauss. This is, as far as I can tell, pure imagination. The Rolex Submariner, assuming it complied with the ISO 6425 for dive watches should be able to resist a 60 Gauss magnetic field. In fact Rolex makes no claim to resist 1000 Gauss for the Submariner. As for an supposed “industry standard” for all mechanical watch movements to resist magnetic fields of 1000 Gauss I cannot find any evidence whatsoever for the existence of this standard. If Deployant has any evidence for this supposed “industry standard” or for the ability of the Rolex Submariner to resist a magnetic field of 1000 Gauss I would be grateful for any such information.