Archive
09/28/2018 – Ephemeris – The GTAS will be at the Acme Fall Festival tomorrow
Ephemeris for Friday, September 28th. The Sun will rise at 7:37. It’ll be up for 11 hours and 51 minutes, setting at 7:28. The Moon, half way from full to last quarter, will rise at 9:44 this evening.
The Grand Traverse Astronomical Society will be at the Acme Fall Festival tomorrow, that’s Saturday September 29th from 10 to 4 p.m. It will be held at Flintfields Horse Park on Bates Road, north of M72. The society members will bring their telescopes which will be used to view the Sun, and Venus if it’s clear. There will also be exhibits of astronomical photos from NASA, professional and our own amateur astronomers. As the festival and star party year winds down and the school year begins members of the society can bring astronomy and space to the classroom. Plus the society is beginning to plan for next year. Contact the Grand Traverse Astronomical Society via email at info@gtastro.org.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Acme Fall Festival 2017 View 1. Credit Bob Moler 
Acme Fall Festival 2017 View 2. Credit Bob Moler
09/27/2018 – Ephemeris – Twilight zone
Ephemeris for Thursday, September 27th. The Sun will rise at 7:35. It’ll be up for 11 hours and 54 minutes, setting at 7:30. The Moon, 3 days past full, will rise at 9:12 this evening.
It will get dark tonight with the end of astronomical twilight at 9:11 p.m., and a minute later the bright Moon will rise spoiling the dark sky. Speaking of astronomical twilight there are three twilight periods: Civil, Nautical and Astronomical. In the evening civil twilight lasts from sunset to when the Sun drops to 6 degrees below the horizon. The scene around is still quite bright, but car headlights still need to be on. Nautical twilight lasts until the Sun is 12 degrees below the horizon. Bright stars and the horizon are visible for sextant use. After that is astronomical twilight until the Sun is 18 degrees below the horizon, when the stars become more and more numerous. After that it’s officially dark, Moon willing.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
More information about twilight, dusk and dawn can be found here: https://www.timeanddate.com/astronomy/different-types-twilight.html.
09/26/2018 – Ephemeris – Wednesday os bright planet day on Ephemeris
Ephemeris for Wednesday, September 26th. The Sun will rise at 7:34. It’ll be up for 11 hours and 57 minutes, setting at 7:32. The Moon, 2 days past full, will rise at 8:43 this evening.
Let’s look at the bright planets today. Four of them are visible in the evening sky. The brilliant Venus will be visible in the western twilight briefly from about 7:50 p.m. until it sets at 8:14 p.m. Jupiter will be in the southwest as it gets dark. It is only outshone by Venus, and the Moon. The big planet will set at 9:24 p.m. Saturn will start the evening low in the southern sky and will stay relatively low, above the Teapot of Sagittarius. It will be due south at sunset and will set at 11:54 p.m. Mars will be low in the south-southeast as the skies darken tonight. and is now 53.5 million miles (86.2 million km) away. Mars will be due south at 9:48 p.m., and it will set at 2:14 a.m. It’s diameter is 16.4 seconds of arc, quite small in telescopes.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Here are the apparent diameters of the above planets:
Venus 43.7″ (seconds of arc)
Jupiter 32.8″
Saturn 16,6″, rings 38.6″
Mars 16,4″
Jupiter’s moon Ganymede will begin to transit the planet at 8:50 p.m. EDT (00:50 UT September 27).
09/25/2018 – Ephemeris – The harvest moon effect
Ephemeris for Tuesday, September 25th. The Sun will rise at 7:33. It’ll be up for 12 hours and 1 minute, setting at 7:34. The Moon, 1 day past full, will rise at 8:17 this evening.
The full, or nearly full moon, just rising, looks like a large orange pumpkin. The color, like the red of the sunset is caused by the scattering out of blue light by the atmosphere. It can happen at any full moon, not just the Harvest Moon, which was officially yesterday. What the Moon around the Harvest Moon does do is rise only a little later each evening. This helped the farmers in earlier times extend daylight to bring in the crops. On average the moon rises or sets 50 minutes later each night. However when the Moon is in the part of the sky where it is moving northward as well as eastward, then it rises only a little later each night. Tomorrow’s Moon will rise only 27 minutes later than it will this evening.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
09/24/2018 – Ephemeris – The harvest moon and the Chinese Mid-Autumn Festival
Ephemeris for Monday, September 24th. The Sun will rise at 7:32. It’ll be up for 12 hours and 4 minutes, setting at 7:36. The Moon, at full today, will rise at 7:51 this evening.
Tonight at 10:53 p.m. the Moon will be full. And since it’s only two days past the autumnal equinox, this makes it the Harvest Moon. This full moon also marks the Chinese Mid-Autumn Festival to honor the Moon and the story of Chang’e a mortal woman to took an elixir and flew off to the Moon and became a goddess. Another story revolves around the Jade Rabbit pounding Medicine. I talked about the figure of a rabbit seen on the face of the Moon last Monday. He is a companion to Chang’e, and has a mortar on the Moon with him. He pounds out the medicine that makes the inhabitants of the sky immortal. The Chinese lunar probes are named Chang’e. Chang’e 3 landed on the Moon in 2013 and sent out a lunar rover named Yutu , the Jade Rabbit.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Chang’e 3 Lander on the Moon. Credit China National Space Administration 
Yutu Rover on the Moon. Credit China National Space Administration.
09/21/2018 – Ephemeris – Twilight talk and star, actually planet, party tonight in Thompsonville
Ephemeris for Friday, September 21st. The Sun will rise at 7:28. It’ll be up for 12 hours and 13 minutes, setting at 7:42. The Moon, 3 days before full, will set at 4:44 tomorrow morning.
Tonight members of the Grand Traverse Astronomical Society will hold a twilight talk and a star party at the Betsie Valley District Library in Thompsonville. It starts at 7 p.m. with a talk about how the Moon came to be and the features that will be visible tonight by yours truly. Where did the Moon come from? That mystery has baffled astronomers for ages. The rocks the Apollo astronauts brought back from the Moon offer clues to a possible answer. After which the Moon, Mars and Saturn will be visible. If cloudy, the talk will go on as scheduled, though the observing part of the evening will be replaced with a look at the skies via computer projection and a preview of the autumn season in the skies.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
09/20/2018 – Autumn will fall on us Saturday night
Ephemeris for Thursday, September 20th. The Sun will rise at 7:27. It’ll be up for 12 hours and 16 minutes, setting at 7:43. The Moon, half way from first quarter to full, will set at 3:44 tomorrow morning.
Welcome to the last few days of summer. The weather has stayed summery thus far through September. The Sun will reach the autumnal equinox point in the sky at 9:54 Saturday evening. At that moment the Sun will cross the celestial equator, a projection of the Earth’s equator, heading southward. All locations on the Earth except two will experience 12 hours of daylight and 12 hours of night. Well they would if the Earth didn’t have an atmosphere and sunset and sunrise were defined differently. The two locations that don’t experience equal night, which is what equinox means, are the north pole where the Sun will be setting and the south pole where the Sun will be rising. For us in the northern hemisphere daylight hours will be shorter and the Sun will peak lower in the south each day until the December solstice.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
