Top of Form Presented
is a very rare professional grade, marine sextant artificial horizon adapted from the military Fairchild
A10A Bubble Sextant by John Luyx of the InfoCenter, Forestville, MD20753 in the late 1980s. We can find no record of them on the internet. This bubble
horizon is fully functional and provides accurate results when compared to a known geographic position. See Statement of Condition.This type of artificial
horizon is one of the few that has an adjustable bubble. The early Carl Plath sextant horizons did as well, but as a cost-saving measure, the feature was discontinued from the next two generations they made before stopping sextant production. The
Cassens & Plath horizon which is still available has a fixed size bubble.
A10A Marine variant. Various views around the clock INCLUDED ARE: The device comes with
5 pages of documentation and instructions prepared by InfoCenter including Index Correction and a working external
night light.The external light illuminates the bubble image at twilight and enhances
the image in the bubble chamber. A wood display stand is also included.
The new owner will also
receive an A10A bubble Horizon Reconditioning Manual in the form of a CD-ROM which has extensive information and numerous
excellent photographs. The digital-manual, was authored by Bill Morris of New Zealand. He is an engineer whose passion
is analyzing the technical aspects of sextant design.
WW II Fairchild
A10A Bubble Sextant

A10A Marine Variant with
light attached

Theoretically,
bubbles are simple to use by providing an artificial horizon using a bubble as a horizontal and vertical
reference. The bubble is centered at the midpoint of the viewing chamber and the celestial body is brought into
coincidence with the bubble’s center.
SUITABLE SEXTANTS: The bubble horizon attachés to the sextant in the normal
way with a rising piece or fork that fits either C. Plath, Cassens & Plath, Astra III B and
Tamaya sextants. .
MODIFIER: John Luyx is said to have had a Merchant
Marine or Navy background, He had a business association with Boat US in the late 1980’s and early 1990’s selling
Chinese sextants imported by Boat US under the Aries brand name. This was the same sextant that Celestaire helped develop
and now controls exclusively in the U.S.
as the Astra III B under their joint venture agreement with the factory.

THE SEXTANT PICTURED IS NOT INCLUDED
CONDITION: The unit is complete with all parts including the
working external night light, four non-original dimmers for adjusting ambient light to the bubble chamber, and two shades
for the Sun. It is full of Xylene, the solution used in the bubble chamber. It is possible to successfully
adjust the size of the bubble, to whatever size is appropriate for the bodies to be shot. This may be from 1/3 to 1/2
the diameter of the chamber.
Before reducing the size of the bubble we tried the device on a Tamaya MS 833 and
achieved progressively better results. In only taking a few practice
sights, morning and afternoon, I was able to get LOP’s withing 3 1/2 miles of our known position for the second set and 2.2
NM for the third set. With the smaller size bubble we are able to repeat sights within 1 NM.
Consequently,
this unit is perfect for a seagoing navigator who is looking for a marine bubble horizon in excellent condition or a
collector for its historic significance. It is also ideal for taking practice sights while ashore as discussed in SUGGESTED
USE below.SUGGESTED USE: The bubble horizon has a
2 power optical system and a smaller than normal field of view. The internal dampening mechanism of the bubble is greater
than will be found on less costly alternatives, but requires some practice in getting used to. This type bubble
horizon is far superior to a normal artificial horizon which can only be used for objects with altitudes of less than 60 degrees
and can not be used for twilight sights. This makes it ideally suited for land based training applications, for land navigation
and for use at sea from ships large enough to be a stable platform. Interestingly, in the 1970-80’s this device, in an
earlier form, was issued to U.S. submarines for back-up celestial navigation. Ref. Dutton’s Seamanship & Navigation, 12th
Edition, Article 2206, page 385.
Bottom of Form

Shown with example
of documentation A10A MARINE VARIANT BUBBLE HORIZON SPECIFICATIONS: MARKINGS: There are no markings
Magnification
2 X estimated
4 3/4″ H x 2 1/2″ L x 1 3/4″ D
4 plastic ambient light dimmers
2 Sun shades

Weight: 7 oz

This
device is suited for someone who can appreciate the fine points of its design, and is willing to pay an appropriate price
for its innovation and historic significance