Twilight is the time between dawn and sunrise or between sunset and dusk, during which sunlight scattering in the upper atmosphere illuminates the lower atmosphere, and the surface of the earth is neither completely lit nor completely dark. The sun itself is not directly visible because it is below the horizon. Owing to the distinctive quality of the ambient light at this time, twilight has long been popular with photographers, who refer to it as Sweet Light, and painters, who refer to it as the "blue hour", after the French expression l'heure bleue.
The collateral adjective for twilight is crepuscular; it is most frequently encountered when applied to certain insects, fishes, mammals, and cachers that are most active during that time.
A solstice is an astronomical event that occurs twice each year as the sun reaches its highest or lowest excursion relative to the celestial equator on the celestial sphere. As a result, on the day of the solstice, the sun appears to have reached its highest or lowest annual altitude in the sky above the horizon at local solar noon. The word solstice is derived from the Latin sol (sun) and sistere (to stand still), because at the solstices the sun stands still in declination; that is, the seasonal movement of the sun's path (as seen from Earth) comes to a stop before reversing direction. The solstices, together with the equinoxes, are connected with the seasons. Typically, the solstices mark either the beginning or the midpoint of winter and summer. The cumulative cooling and warming that result from the tilt of the planet become most pronounced after the solstice, leading to the more recent, western, custom of using them to mark the beginning of summer and winter.
(is this another clue?)
Winter Solstice in East Asia
The traditional East Asian calendars divide a year into 24 solar terms: Dōngzhì (or in Vietnamese for example: Đông chí; which is literally "winter's extreme") is the 22nd solar term, and marks the winter solstice. While a solstice is typically observed over a ten day period, Dōngzhì most often refers in particular to that day when the sun is exactly at the celestial longitude of 270°. The solstices (as well as the equinoxes) mark the middle, or the summit, of the seasons in East Asian calendars.
Civil dawn twilight
Morning civil twilight begins when the geometric center of the sun is 6° below the horizon (civil dawn) and ends at sunrise. The brightest planets can appear during this time. Venus, the brightest planet as observed from the Earth is known as the "morning star" due to its visibility during civil twilight. There is enough light from the sun during this period that artificial sources of light may not be needed to carry on outdoor activities.
This concept is sometimes enshrined in laws, for example, when drivers of automobiles must turn on their headlights; when pilots may exercise the rights to fly aircraft; restrictions on hunting; or if the crime of burglary is to be treated as nighttime burglary, which carries stiffer penalties in some jurisdictions. A fixed period (most commonly 30 minutes before sunrise) is typically used in such statutes, rather than how many degrees the sun is below the horizon. Civil twilight can also be described as the limit at which twilight illumination is sufficient, under clear weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, the horizon is clearly defined and the brightest stars are visible under clear atmospheric conditions.
Solstice Celebration
The term solstice is used in a broad sense as the date (day) when the sun pauses over a tropic (such as the northern, tropic of Cancer, for a southern winter solstice). The day of the winter solstice is therefore the shortest day of the year for any place south of the equator.
Most cultures celebrate a solstice, usually the most extravagant holidays of any community’s calendar (eg: Christmas, Saturnalia, Kwanzaa, Hanukah, Litha, Setsubun, Makara Sankranti, Karkat Sankranti and Aymara). Geocachers like celebrations too. More darkness will not interrupt a geocacher with access to a torch.
The Event
This event is only for the duration of Civil dawn twilight on the day of the Winter Solstice. That is, commencing promptly at 06:12 (yes, in the morning) of Friday 21st June 2013, and you are requested to sign the logbook prior to sunrise at 06:37. At that time the logbook will be closed.
The location is on a small lookout over the river, facing east. If it is raining, then the event, logbook and photo will be moved to the alternative location coordinates nearby.
That's it. Please note that this is a school day morning, so you may need to get permission before logging a 'will attend'.
Afterwards
Afterwards you may do what and where you wish, legally, however at the alternative coordinates is a council-provided BBQ, and one picnic table (another one not too far away as well). I will be hanging around and making myself some breakfast - and coffee will once again be available. 