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Piston and tilt are not actually true optical aberrations, as they do not represent or model curvature in the wavefront. Defocus is the lowest order true optical aberration. If piston and tilt are subtracted from an otherwise perfect wavefront, a perfect, aberration-free image is formed. Rapid optical tilts in both X and Y directions are termed ...
Lift due to incidence, this is negative because the z-axis is downwards whilst positive incidence causes an upwards force. Z q {\displaystyle Z_{q}} Lift due to pitch rate, arises from the increase in tail incidence, hence is also negative, but small compared with Z α {\displaystyle Z_{\alpha }} .
If instead of the actual head tilt (as compared to true vertical), the direction of the head tilt as interpreted by the brain (subjective head tilt) is given importance, then it is seen that the head tilt and ocular torsion are actually in the same direction in both the physiologic ocular counter-roll and the pathologic ocular tilt reaction.
In geometry, dihedral angle is the angle between two planes. Aviation usage differs slightly from usage in geometry. In aviation, the usage "dihedral" evolved to mean the positive, up angle between the left and right wings, while usage with the prefix "an-" (as in "anhedral") evolved to mean the negative, down angle between the wings.
A celestial object's axial tilt indicates whether the object's rotation is prograde or retrograde. Axial tilt is the angle between an object's rotation axis and a line perpendicular to its orbital plane passing through the object's centre. An object with an axial tilt up to 90 degrees is rotating in the same direction as its primary.
The positive tilt is thus the building phase of the trough and the negative tilt is the dissipation of its energy. Therefore, the clouds and precipitation will develop in the positive phase and the most severe weather will be in the negative phase. [8]
Therefore, greater tilt means a lower minimum for the same maximum: less total annual surface insolation at the equator. At the poles (90° latitude), on the equinoxes and during polar night , the sun angle is always 0° or less no matter the axial tilt, while on the summer solstice, the maximum angle is equal to the tilt.
In most cases, two thin lenses are combined, one of which has just so strong a positive aberration (under-correction, vide supra) as the other a negative; the first must be a positive lens and the second a negative lens; the powers, however: may differ, so that the desired effect of the lens is maintained. It is generally an advantage to secure ...