BMCT

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Begin Morning Civil Twilight (BMCT) is a military term defined by the Department of Defense (DoD) of USA.

It defined as the period of time at which the sun is halfway between beginning morning and nautical twilight and sunrise, when there is enough light to see objects clearly with the unaided eye.

At this time, light intensification devices are no longer effective, and the sun is six degrees below the eastern horizon.