Age (Moon)

The time that has elapsed since the last new moon.

Altitude

The height of an object (or a location on the Earth's surface) above sea level. Learn more on Wikipedia.

Aperture

The adjustable aperture in a camera controls the amount of light that will reach the film or digital sensor. The size of such an opening is called the f-stop, it is written f/5.6. The smaller the aperture, the larger the diaphragm. Learn more about Wikipedia.

Aperture (critical for depth of field)

It gives the best basis for the image with optimal diffraction, but the sharpness range will be the smallest.

Aperture (optimal for depth of field)

It gives an image with the greatest range of sharpness.

Aperture (beneficial for depth of field)

It gives an image with just a blur but we will have a limited diffraction for the eyes.

Astronomical Twilight

Astronomical twilight (morning and evening) is the time when the center of the sun is between 12° and 18° below the horizon (-12º,-18º). From the end of astronomical twilight in the evening to the beginning of astronomical twilight in the morning, the sky is dark enough for all astronomical observations. Learn more on Wikipedia.

Azimuth

The angle between a celestial body (sun, moon, …), measured clockwise around the observer's horizon and the North. It determines the direction of the celestial body. So a celestial body due North has an azimuth of 0°, one due East 90°, South 180° and West 270°. Learn more on Wikipedia.