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12/14/2017 – Ephemeris – The Moon wanders over to Jupiter this morning

December 14, 2017 1 comment

Dec 14. This is Bob Moler with Ephemeris for Thursday, December 14th. The Sun will rise at 8:11. It’ll be up for 8 hours and 50 minutes, setting at 5:02. The Moon, half way from last quarter to new, will rise at 5:26 tomorrow morning.

This morning the planet Jupiter will appear right below the crescent Moon. Jupiter is hard to miss, even without the Moon to point it out. It is with the rare exception of Mars when being its closest to the Earth the second brightest of the planets, after Venus. Speaking of Mars, which is to the upper right of Jupiter and has a reddish hue, if you’re going to send anything to Mars, next spring is the time to do it. Flight times to Mars are 6 to 7 months. The midpoint of the flight is when Mars is closest to the Earth, which next year is July 31st. NASA’s Insight Lander, grounded in 2016 due to an instrument failure has to wait 26 months for the next launch opportunity in May of next year.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Moon, Jupiter, Mars

The Moon, Jupiter and Mars this morning, December 14, 2017. Earth shine should be visible as shown, though not as prominent. Created using Stellarium.

Hohmann orbit to Mars

A Hohmann lowest energy transfer orbit to Mars. This diagram is for the Mars Exploration Rovers Spirit and Opportunity launched in 2003, arrived in 2004. Solid planets, Spirit launch and arrival. Ghost planets, Opportunity launch and arrival. Credit NASA/JPL.

What’s a Hohmann transfer orbit?  NASA explains.

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12/08/2017 – Ephemeris – The earliest sunset of the year is tomorrow night

December 8, 2017 1 comment

Ephemeris for Friday, December 8th. The Sun will rise at 8:06. It’ll be up for 8 hours and 55 minutes, setting at 5:02. The Moon, 2 days before last quarter, will rise at 11:04 this evening.

In thirteen days we will have the shortest day in terms of daylight hours. But the change isn’t uniformly distributed in the morning and evening. Tomorrow evening we will have the earliest sunset. Sunset times have been within the same minute for the last few days and will continue for the next few. The latest sunrise will occur on January second. The reason is that the Sun is traveling faster eastward than average, so the Earth’s rotation takes a little longer each day to catch up with it. Near the solstice the Sun is at a higher latitude, where the longitude lines are closer together, also the Earth is nearing its closest to the Sun, so moves faster its orbit adding to the effect. The effect exists in June but isn’t as noticeable.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

I had more complete thoughts about earliest and latest sunrises and sunsets earlier this year: https://bobmoler.wordpress.com/2017/03/13/03132017-ephemeris-more-thoughts-about-yesterdays-time-change/. Check the addendum.

 

12/05/2017 – Ephemeris – A flat Earth, come on, really?

December 5, 2017 Comments off

Ephemeris for Tuesday, December 5th. The Sun will rise at 8:03. It’ll be up for 8 hours and 58 minutes, setting at 5:02. The Moon, 2 days past full, will rise at 7:35 this evening.

Last Friday night I gave a talk to the Grand Traverse Astronomical Society about the world view of mostly ancient peoples. They uniformly believed in a flat Earth. This includes the world of the Bible. The Greek geographer Eratosthenes calculated the circumference of the Earth way back in the third century BC. A flat Earth would normally be the conclusion of a person who never went more than a few hundred miles from home, especially in an east-west direction. However if one went north or south, the stars would slowly change. Head south and new stars would appear above the southern horizon, and in the north, stars that would never set would now set. Polaris would drop lower in the North. The round Earth is the simplest explanation.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Here’s an extension from my notes:

Those who profess to believe in a flat Earth tend to be Christian and believe that the Bible is literally true even to the physical description of the world found in its pages. Therefore the basis for the flat Earth is the Bible.

While there are those who have always believed in a flat earth, Eratosthenes pretty much put killed that notion in the 3rd century BC when he found that there was a 7.2 degree difference in the altitude of the Sun at local noon on the summer solstice between Syene and Alexandria in Egypt. The distance between the two cities was about 800 km, and 7.2 degrees is 1/50th that of a circle, so the Earth would have been 50 X 800 or 40,000 miles in circumference. This of course meant that the Earth was round! The units he used were stadia, whose exact length has been in doubt.

Flat earth theories started to proliferate in the mid-19th century when most of the Earth’s coastlines had at least been mapped, though the polar regions had yet to be breached.

Zetetic Astronomy. Earth not a globe! An experimental inquiry… by Samuel Birly Rowbotham, 1865
Zetetic Cosmology: Conclusive evidence that the world is not a rotating-revolving-globe, but a stationary flat pane circle, second edition, by “Rectangle”, 1899. Rectangle is a pseudonym of T. Winship
These can be found on Archive.org.

The latest reincarnation of the Flat Earth Society was started in 2013.  Their web page and wiki is here:  https://www.tfes.org/.

Flat Earth

The Flat Earth by Trekky0623 at English Wikipedia, placed in the Public Domain.

Features:

  • North Pole in the center.
  • The firmament rotates around it.
  • There is no South Pole.
  • There are impassable mountains in Antarctica at the end of the Earth.
  • Wouldn’t the Sun be always up for everybody?
  • Apparently the Sun orbits over the flat Earth in circles between the Tropic of Cancer and Tropic of Capricorn to produce the seasons.
  • The Sun is 3000 miles away and is only about 30 miles in diameter.
  • It shines like a spotlight over the earth.
  • The moon is somewhat lower than the sun and can cause solar eclipses.
  • The flat Earth’s shadow cannot cause a lunar eclipse, since the Moon is on the same side of the Earth as the Sun. The eclipse is caused by a “shadow object” that we can’t see that comes between the Sun and the Moon.

It boggles my mind how anyone in this day and age, who travels a lot cannot believe that the Earth is a spheroid. Maybe no one looks up any more. Perhaps I’m just an oddball astronomer who like to look up and see the stars shift as I move south or north. In fact I plan on it when I travel.

11/28/2017 – Ephemeris – Though it appears bright, the Moon is pretty dirty

November 28, 2017 1 comment

Ephemeris for Tuesday, November 28th. The Sun will rise at 7:56. It’ll be up for 9 hours and 8 minutes, setting at 5:04. The Moon, 2 days past first quarter, will set at 2:44 tomorrow morning.

The Moon tonight is a waxing gibbous phase, and each night until it’s full it will get brighter and brighter, drowning out the fainter stars. The Moon is almost too bright to comfortably view in a telescope. One can get a moon filter for the eyepiece, or wear sunglasses or opt for higher magnification. It is after all daytime on the Moon and it’s essentially the same distance from the Sun as we are. A saving grace is that the Moon isn’t white. It’s a dirty gray, reflecting on average only 13.6 percent of the light it gets from the Sun. Just think how bright it would appear if it were 100% reflective, over 7 times brighter than it appears now. The face of the Moon hasn’t appeared to change at all since before we landed there 48 years ago.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Moon albedo comparison

Moon albedo comparison. Actually about 50% vs. 100%. The Moon is less reflectant than that.. Sunday’s super moon image created via Stellarium.

11/23/2017 – Ephemeris – Mercury is at it’s greatest eastern elongation tonight

November 23, 2017 1 comment

Ephemeris for Thanksgiving Day, Thursday, November 23rd. The Sun will rise at 7:49. It’ll be up for 9 hours and 17 minutes, setting at 5:07. The Moon, 3 days before first quarter, will set at 9:33 this evening.

Mercury is going to reach its greatest elongation or apparent separation from the Sun this evening. It will be 22 degrees east of the Sun. Because Mercury is the closest planet to the Sun, it is never seen far from it. And because it has the most eccentric orbit of all the planets its greatest elongations are between 17 and 27 degrees from the Sun. Other than that the best times of the year to see Mercury are late winter and early spring evenings and late summer and early autumn mornings. Being an autumn evening means that Mercury is almost too low to spot after sunset. The southern hemisphere is in spring, so Mercury tonight will be much easier seen. Also their best view is when Mercury is farther from the Sun.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

There are rather clinical charts.  The horizontal line through the W (western compass point) is the horizon.  Grid marks are 10 degrees apart.

Mercury from  45 degrees north

Diagram showing the poor placement of Mercury at greatest eastern elongation tonight in autumn from 45 degrees north latitude. Mercury is about 8.5 degrees altitude at sunset. The orange line is the ecliptic, the path pf the Sun on the celestial sphere. Created using Stellarium.

Mercury at sunset at E elong S 45 Lat_112317

Diagram showing the great placement of Mercury at greatest eastern elongation tonight in southern hemisphere spring from 45 degrees south latitude. Mercury is nearly 19 degrees altitude at sunset. The orange line is the ecliptic, the path pf the Sun on the celestial sphere. Created using Stellarium.

08/28/2017 – Ephemeris – Polaris the North Star

August 28, 2017 1 comment

Ephemeris for Monday, August 28th. The Sun will rise at 7:00. It’ll be up for 13 hours and 25 minutes, setting at 8:25. The Moon, 1 day before first quarter, will set at 12:19 tomorrow morning.

The bright star Polaris is a very important star. It is also known as the North Star and the Pole Star. Its unique position is nearly directly at the zenith at the Earth’s north pole, making it a very important navigational star. It’s about 40 minutes of arc, or about one and a third Moon diameters away from the extension of the Earth’s axis into the sky. As a rule of thumb, it’s angular altitude above the northern horizon is approximately one’s latitude, and it stands about at the due north compass point. Polaris is found using the Big Dipper, using the two stars at the front of the dipper bowl to point to it. It’s located at the tip of the handle of the very dim Little Dipper, which this time of year in the evening appears to standing on its handle.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Polaris Finder Chart

Polaris finder chart for 10 p.m., August 28th. Created using my LookingUp program

Rotation of the sky around Polaris

Animation of the rotation of the sky around Polaris on the night of August 28/29, 2017. Created using Stellarium and Filmora.

I’ve left the constellation lines off.  The Big Dipper is seen easily as is Cassiopeia’s “W” opposite it around the stationary Polaris.

 

 

08/08/2017 – Ephemeris – The Harvest Moon effect starts showing up 2 months early

August 8, 2017 1 comment

Ephemeris for Tuesday, August 8th. The Sun rises at 6:37. It’ll be up for 14 hours and 20 minutes, setting at 8:58. The Moon, 1 day past full, will rise at 9:34 this evening.

The Harvest moon is nearly 2 months away, but some of its effects are starting to be felt now. I call it the Harvest Moon Effect. The Harvest Moon is a bit late this year, October 5th. It’s defined as the nearest full moon to the autumnal equinox. However from August to October the rising times of the full Moon and nights after for the next week don’t advance very fast. On average the Moon rises 50 minutes later each night. Between tonight and tomorrow night the interval will be 32 minutes. This is kind of a bummer this weekend when the Perseid meteor shower reaches peak. As with most meteor showers, the most meteors seen are after midnight. Saturday night’s Perseid peak has the Moon, six days after full rising at 11:36 p.m.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Moonrise time intervals for the rest of this week:

Date Moonrise Difference
08/08/17 9:34 p.m.
32 minutes
08/09/17 10:06 p.m.
30 minutes
08/10/17 10:36 p.m.
30 minutes
08/11/17 11:06 p.m.
30 minutes
08/12/17 11:36 p.m.
Harvest Moon Effect

Harvest Moon Effect for this week. Note how shallow the path of the Moon is in relation to the eastern horizon. I’ve made the earth transparent so we can see the Moon below the horizon. As the Earth rotates the Moon will rise in a direction parallel to the celestial equator. In contrast the Moon’s path around March is steeper than average, so the interval in consecutive lunar rise times is much longer than the 50 minute average. Created using Cartes du Ciel (Sky Charts).