A glossary of astronomical term may be useful and the following is not intended to be comprehensive. For now it is very small, but it will build up over time.
'Night shining' clouds.
These are wispy clouds visible from high latitudes above the northern horizon for several weeks either side of the summer solstice. White or maybe electric blue in colour, they form in the highest regions of the atmosphere up to 100 km high, on the edge of space. They are made of water vapour but how they form is still controversial. Too tenuous to be seen in the daytime, they are visible in the late twilight light by the Sun below the horizon.
In astronomy, an occultation happens when one object passes in front of and obscures another. The Moon regularly occults stars as it orbits the earth, less frequently it occults planets. Very rarely a planet will occult another planet in the solar system.
Because the Moon is relatively close to the Earth a particular occultation may not be seen from all places, the star or planet may instead appear close to the Moon. Some places may witness a 'grazing occultation' when the star or planet skims the edge of the Moon, going in and out of view behind the lunar mountains.
Jupiter begins ‘retrograde motion’ in early October. As the planets orbit the Sun they move against the background of stars. However the Earth also in motion and this changes our viewing point of any planet. Imagine Jupiter coming to a dead stop; it would still appear to drift back and forth against the stars over the course of a year because of our own planets motion. Add these two motions together and the superior planets (Mars outwards) trace loops in the sky rather than smooth orbital paths. Before opposition these planets appears to stop, then move retrograde (backwards). After opposition they again stop and continue with their direct motion.
The period between the Sun being 12 and 18 degrees below the horizon.
Comes after evening and before morning nautical twilight. At the end of this all astronomical objects, including deep sky objects such as galaxies and nebulae, can be properly observed.
The period between the Sun being 6 degrees below the horizon and sunrise or sunset.
In the evening it starts at sunset and ends when the centre of the Sun has sunk 6 degrees below the horizon. In the morning it starts when the centre of the Sun is 6 degrees below the horizon and ends at sunrise. During civil twilight the horizon is clearly visible and objects can be seen without extra illumination.
The period between the Sun being 6 and 12 degrees below the horizon.
Comes after evening and before morning civil twilight. At sea, navigation using the horizon as a reference is not possible because it is no longer visible. By the end of nautical twilight the sky is dark enough for many astronomical purposes.