Archive
06/26/2023 – Ephemeris – After the latest sunset, a look at the Moon
This is Ephemeris for Monday, June 26th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:59. The Moon, at first quarter today, will set at 2:02 tomorrow morning.
Tonight is the night of the latest sunset. From now to December 10th the Sun will be setting earlier than the night before. It won’t be noticeable at first, but the change will increase throughout the summer. The Moon actually arrived at first quarter phase early this morning, so by tonight it will appear slightly gibbous. The term gibbous actually means hump-backed, and the Moon will appear more so as it advances toward being fully illuminated a week from now. For me personally, I find that the best time to view the Moon with a telescope is within three or four days from its quarter phase, unless I’m looking at a specific feature. That’s when shadows are front and center on the moon. The Moon being gray on gray, shadows keep the Moon from appearing flat.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.
Addendum
06/15/2023 – Ephemeris – Today we have the earliest sunrise of the year
This is Ephemeris for Thursday, June 15th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:30, and it will rise tomorrow at 5:56. The Moon, 3 days before new, will rise at 4:28 tomorrow morning.
Today is the day of the earliest sunrise, though the time will stay within the same minute for a few days. In six days the Sun will reach it’s farthest north in our sky. And be above the horizon for fifteen hours and thirty four minutes. That’s the summer solstice for those living in the north hemisphere. It’s also known as the longest day. The retired computer programmer in me likes to take things literally, so no, June 21st, the summer solstice is not the longest day. It’s 24 hours long, like any other day, however it has the longest daylight hours. Daylight hours being defined as the time interval from sunrise to sunset, which, in Interlochen and Traverse City, is 15 hours 34 minutes. Five or six days later, we’ll have the latest sunset.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.
Addendum
If the Earth had no axial tilt and had a circular orbit of the Sun, The earliest sunrise and latest sunset would occur on the summer solstice. But since that is not the case the Earth’s axial tilt and elliptical orbit cause the the earliest sunrise and latest sunset to differ from each other and the summer solstice.
06/15/2021 – Ephemeris – Today we had the earliest sunrise of the year
This is Ephemeris for Tuesday, June 15th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:30, and it will rise tomorrow at 5:56. The Moon, 2 days before first quarter, will set at 1:29 tomorrow morning.
Today is the day of the year with the earliest sunrise, which in the Interlochen/Traverse City area is 6:56 am. We are 5 days before the summer solstice, the longest day in terms of sunshine hours. With the Sun nearing its maximum angle above the celestial equator, the projection of the Earth’s equator on the sky it cuts those longitude timelines quicker because they are closer together than at the equator. This is counters somewhat the Sun’s speed slowing down as the Earth is reaching the farthest point in its orbit. The latest sunset will occur about June 26th, a span of 11 days. In December the span between the earliest sunset and latest sunrise because of the Sun’s increased speed, by being nearly at its closest to us, is 24 days.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
How the Sun’s declination affects how rapidly it appears to cross time lines (meridians)
These graphs show how the earth’s orbit eccentricity and tilt of the Earth’s axis (obliquity) affect sundial time keeping vs. actual clocks. This also affects sunrise and sunset times. The figure 8 in the lower right is the analemma, sometimes seen on old Earth globes, a graphical representation of the equation of time (sundial corrections from apparent to mean solar time).
Table of Earliest and Latest Sunrises and Sunsets during the year for Interlochen/Traverse City area of Michigan. This table was created for 2017, 4 years ago. However, the instant of the summer solstice occurred just after midnight on June 21st, That instant slipped back into just before midnight in 2021. This is why we use the Gregorian calendar. The slide is corrected by having 3 out of four century years being normal years.
06/26/2018 – Ephemeris – Latest sunset of the year
Ephemeris for Tuesday, June 26th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:59. The Moon, 2 days before full, will set at 5:42 tomorrow morning.
Today is the day of the latest sunset, at least for around latitude 45 degrees north. It will be within the same minute for the next 5 days, before it retreats. By the end of July sunset will be at 9:09 p.m. The lopsidedness of the dates of earliest sunrise and latest sunset is caused by two factors. The Sun’s high latitude or declination above the equator, which makes it appear to move faster, countered in the summer by the fact that the Earth is almost at its farthest from the Sun, which makes it appear to be slower. These effects are why sundials don’t keep proper clock time without the adjustment of the equation of time to the readout, or fancy sundials that take that into account.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
In a post from last year I looked at the equation of time: https://bobmoler.wordpress.com/2017/03/13/03132017-ephemeris-more-thoughts-about-yesterdays-time-change/
06/16/2014 – Ephemeris – Dates of the earliest sunrise and latest sunset
Ephemeris for Monday, June 16th. Today the sun will be up for 15 hours and 33 minutes, setting at 9:29. The moon, half way from full to last quarter, will rise at 12:11 tomorrow morning. Tomorrow the sun will rise at 5:56.
Yesterday saw the earliest sunrise for the year. My sunrise times will start to show a change on Thursday. The day-to-day change in sunrise times are now a few seconds. The summer solstice, or longest day will be this Saturday, and the latest sunset won’t occur until next week Thursday. The reason these dates don’t coincide has to do with the tilt of the earth’s axis and the earth’s slightly elliptical path around the sun. Actually the disparity between these dates is more pronounced at the winter solstice when the Earth is closer to the sun and moving faster. Yup, the sun is farther away now than it was in December. Actually we’re moving slower now, so summer lasts a few days longer than winter.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Bob Moler's Ephemeris Blog 