| The period of time before sunrise or after sunset where the midpoint of the sun disk is 12 degrees or less below the true horizon |
| The period of time before sunrise or after sunset where the midpoint of the sun disk is 6 degrees or less below the apparent horizon. |
| The period of time before sunrise or after sunset where the midpoint of the sun disk is 6 degrees or less below the true horizon. |
| The period of time before sunrise or after sunset where the midpoint of the sun disk is 12 degrees or less below the apparent horizon. |
EN 