Event Date: June 13th
Time: 5:14(.51) AM
Brief
Ending a three-morning series showing each phase of twilight beginning, the time for the image shows that for civil twilight's start; when the Sun is 6º below the horizon and a short while before rising. As I mentioned at the end of yesterday's entry, I will include the celestial grid this time to show why I talk about an average duration of each twilight phase. Looking at the grid, with the horizon showing, I also hid the landscape panorama. This way, we can see that the further north the grid circles get, the less of a "slope-up" the Sun makes while rising. Only the Andromeda Galaxy remains labeled, as the other deep sky that I labeled over the last two mornings are either too small in angular size to easily see, or become washed out by the Sun.
Time: 5:14(.51) AM
Brief
Ending a three-morning series showing each phase of twilight beginning, the time for the image shows that for civil twilight's start; when the Sun is 6º below the horizon and a short while before rising. As I mentioned at the end of yesterday's entry, I will include the celestial grid this time to show why I talk about an average duration of each twilight phase. Looking at the grid, with the horizon showing, I also hid the landscape panorama. This way, we can see that the further north the grid circles get, the less of a "slope-up" the Sun makes while rising. Only the Andromeda Galaxy remains labeled, as the other deep sky that I labeled over the last two mornings are either too small in angular size to easily see, or become washed out by the Sun.
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Detailed
Here's a review from two entries ago: the further north of east the Sun rises, as the case of this time of year, the less of a slope during astronomical twilight. The angle that the Sun rises relative the rises starts small and stays that way a little longer than at the equniox. At this time of year for most mid-northern latitudes, the duration of astronomical is about 43 - 44 minutes, while nautical is 39 - 40 minutes. Civil ends up being the shortest, at only 31 - 32 minutes. The slight variance for each, hence my using two number values, depends on the exact date and/or latitude. During the winter once again, these durations are shorter and different in comparison to each other
Now that we have reached our earliest Sunset, our star will start rising later, although very gradually by seconds, during the rest of this month. Rather than me posting the Sunrise time each day or mentioning it, try doing so yourself when looking east-northeast. Even if there is hill, house or tree obstruction, we will notice a difference between now and the end of the month.
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