Magnetic declination
The difference between true or geographic north and magnetic. Currently, this value changes because the magnetic pole is moving. Time and Date
Maximum exposure time
Maximum shutter exposure time for stars to appear as dots (and not small traces) or the moon to take an oval shape or lose detail.
Meteor
A celestial object entering the Earth’s atmosphere causing a glow by colliding with air particles in the highest parts of the atmosphere. Also known as shooting star. Time and Date
Meteor shower
Unusual activity of meteors that glow for brief moments in the night sky for a period of a few days or weeks. Depending on the number of meteors per hour it will be of greater or less activity. According to dates and origin of meteors are known by proper names as Perseids (which are meteors from areas of the constellation Perseus), Draconids (by their origin from the constellation Dragon), … Time and Date
Meteorite
Special rock meteor or meteoroid that survives entry into the atmosphere and lands on the Earth’s surface. Time and Date
Meteoroide
Special rock that is composed of dust particles or fragments of comets or asteroids. A meteoroid will become a meteor if it enters Earth’s atmosphere causing a visible glow at night and meteorite if it manages to reach the surface. Time and Date
Meridian
Imaginary line that goes from the north pole to the south pole connecting all locations of the same length.
Above the observer, it is the moment when the sun or moon is at their maximum height. For the sun it’s time for solar noon. Time and Date
Micromoon
Moon that, by its distance to Earth, during the apogee, looks smaller than usual. It is usually only defined during the full moon and new moon phases. Time and Date
Midnight sun
When at least part of the sun is always visible on the horizon 24 hours a day. Also known as polar day. Time and Date
Milky Way
Galaxy to which we belong, visible from Earth as a band of light brighter than the rest of the sky that forms an arc. Wikipedia.
Minimum hyperfocal distance
Distance to the middle of the hyperfocal. From this distance to infinity will be acceptably focused.
Moon
Earth’s natural satellite. Wikipedia.
Moonbows
Rare atmospheric phenomenon caused by reflected and refracted moonlight in water droplets in the air. Moon rainbows that occur in some waterfalls are often highly prized, but can also be seen in sea breaks and during some night drizzle. Time and Date
Moonset
A moment when the moon is no longer visible behind the horizon. Because of refraction in the Earth’s atmosphere, this event occurs after it actually disappears on the horizon. During cloudy days and on new moon dates, the moon will not be visible, even if it is on the horizon. Time and Date
Moonrise
A moment when the moon is visible on the horizon. Because of refraction in the Earth’s atmosphere, this event occurs before it actually appears on the horizon. During cloudy days and on new moon dates, the moon will not be visible, even if it is on the horizon. Time and Date
MW
See Milky Way.