A system of navigation employing an emergency longitude slide ruler for stellar navigation is described. The emergency longitude slide ruler is equipped with several wheels having rulers with settings including of the longitude slide ruler of the present invention include year, date, hour, minutes, star angle measurement degree wheel, a longitude wheel, a circumpolar star field identifier wheel, star meridian transit angles wheel, and a time zone wheel. All wheels are of diminishing diameters and are laid on top of each other in descending circumference with minute gradations allowing each consecutive wheel to line up with its larger adjacent wheel according to proper settings to eventually indicate longitude. The system presents an efficient and expedient means by which an individual with very limited knowledge of navigation and celestial bodies can determine his or her location, including longitude.

Certain embodiments of the disclosure may include systems and methods for calculating the wind deflection of a rifle bullet using concentric scales. The scales are marked radially on each side, one side pertaining to wind speed and the opposite side pertaining to wind direction. The scales of one side include indicia of deflection at various wind speeds, and the scales of the other side include indicia for various wind directions. Using both sides together and in sequence, correction can be made for both wind speed and wind direction.

Certain embodiments of the disclosure may include systems and methods for calculating the wind deflection of a rifle bullet using concentric scales. The scales are marked radially on each side, one side pertaining to wind speed and the opposite side pertaining to wind direction. The scales of one side include indicia of deflection at various wind speeds, and the scales of the other side include indicia for various wind directions. Using both sides together and in sequence, correction can be made for both wind speed and wind direction.

As analog calculator for determining the deflection of a rifle bullet due to the effects of wind speed and wind direction consists of three members. The first member a disc that is marked on both sides with a series of concentric scales. The scales are arranged such that the proper linear relationship of a set of values are aligned radially at all points around the disc. The scales of one side of the disc are arranged for the purpose of solving for bullet deflection due to varying wind speeds. The scales of the opposite side are arranged for the purpose of solving for bullet deflection due to varying wind direction relative to the line of fire. A second and third member are fixed on either side of the first member such that they are free to turn on a central pivot point aligned with the concentric center of the first member. The second member is marked with a key for the respective scales of the first member with which it aligns and an indicator extending radially that establishes the values on the concentric scales of the first member that share the proper relationship for a correct solution for varying wind speeds. The third member is marked with a key for the respective scales of the first member with which it aligns and an indicator extending radially that establishes the values on the concentric scales of the first member that share the proper relationship for a correct solution for varying wind directions. The third member is also marked with a diagram for the determination of the proper scale for the wind direction relative to the line of fire. Both the second and third member are marked with a scale that aligns around the partial circumference of the largest scale of the first member to allow addition or subtraction of values.