03/16/2017 – Ephemeris – Curly Tail, The Great Underwater Panther

March 16, 2017 Comments off

Ephemeris for Thursday, March 16th.  The Sun will rise at 7:52.  It’ll be up for 11 hours and 57 minutes, setting at 7:50.  The Moon, half way from full to last quarter, will rise at 12:03 tomorrow morning.

The Anishinabek people of the Great Lakes Region, which includes the Ottawa, Chippewa and Ojibwe Indians have two constellations of winter that I know of.  The first is The Winter Maker which uses many of Orion’s stars plus Procyon the Little Dog Star.  It rises in the eastern skies in the evening as winter is beginning.  The second is the Curly Tail, the Great Underwater Panther.  Which uses the stars of Leo the lion’s backward question mark as its tail and the small knot of stars that are the head of Hydra the water snake below Cancer as its head.  I imagine this constellation was a warning to youngsters to keep off the thinning ice of spring, lest they fall in and be snatched by the great underwater panther that lives beneath the ice.

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

Addendum

Ojibwe constellations

An animated GIF rotating between an unannotated star field facing south at 10 p.m. March 16th.; Western constellation names and lines for Orion, Hydra, and Leo; Western constellation art, Ojibwe constellation names and lines; and Ojibwe constellation art. Created using Stellarium. The Ojibwe constellation art is supplied as part of the latest version of Stellarium.  Click on the image to enlarge.

The source for the Ojibwe constellation art is from Ojibwe Sky Star Map Constellation Guide (An introduction to Ojibwe Star Knowledge) by Annette S. Lee, William Wilson, Jeffrey Tibbetts, and Carl Gawboy, ISBN 978-0-615-98678-4.  The illustrations are by Annette S. Lee and William Wilson.  There is also a poster sized star map available.  It should be available in book stores locally, or at Amazon.  I found my copy at Enerdyne in Suttons Bay.

Also shown is the Pleiades, which to the Ojibwe is Hole in the Sky, which has to do with the Shaking Tent Ceremony.  The Pleiades is also known as the Sweating Stones, the heated stones used in the Sweat Lodge Ceremony.  In the later spring sky the Sweat Lodge itself is seen in the stars of the Western Corona Borealis.

Note:  As far as tribe names go:  Ottawa = Odawa, and Chippewa = Ojibwe.

03/15/2017 – Ephemeris – Wednesday is bright planet day. Do you know where your planets are?

March 15, 2017 Comments off

Ephemeris for Wednesday, March 15th.  The Sun will rise at 7:54.  It’ll be up for 11 hours and 54 minutes, setting at 7:48.  The Moon, 3 days past full, will rise at 11:04 this evening.

It’s dark enough to see the morning planets during these Ephemeris programs again.  But it won’t last.  Jupiter will be seen in the morning in the southwest above the star Spica, with the bright waning gibbous moon above and left of them.  It will rise tonight at 9:50 p.m. in the east.  Saturn can be glimpsed this morning above the Teapot figure of Sagittarius.  It will rise tomorrow at 3:37 a.m. in the east-southeast.  In the evening sky tonight Venus, low in the west, is diving toward the Sun, though it will pass north of the Sun.  Actually the thin crescent is showing it, canted a bit to the left, rather than to the right as you’d expect.  Ten days and it’s officially outta here, and into the morning sky.   Mars is still hanging on, way above Venus in the west.

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

Addendum

Morning planets

Jupiter, Saturn and the Moon at 7 a.m. this morning, March 15, 2017. Created using Stellarium.

Jupiter and moons this morning

Jupiter and its moons at 7 a.m. (11:00 UT) March 15, 2017. Created using Cartes du Ciel (Sky Charts).

Telescopic Saturn and moons

Saturn and its brightest moons as they might appear in telescopes this morning at 7:00 a.m. (11:00 UT) March 15, 2017. Shown at the same magnification as Jupiter above for comparison of apparent sizes. Created using Cartes du Ciel (Sky Charts).

Early evening planets

Venus and Mars in the west at 8:30 p.m. this evening March 15, 2016. Venus is only 10 days from inferior conjunction with the Sun. Created using Stellarium.

Telescopic Venus

Venus as it might appear in a telescope at 8:30 p.m. March 15, 2017. Created using Hallo Northern Sky.

This is the first time I’ve used an image from Hallo Northern Sky (HNSKY)  I found Hallo Northern Sky a few years ago and found it difficult to use, but its operation has improved with newer releases.  It looks bare bones, like my LookingUp program, but I have yet to plumb all its depths.  It’s really quite sophisticated.  More clinical than pretty.  I have a link to it on the right under Free Astronomical Software.  It produces a better skinny crescent Venus than the other software I have.

Jupiter rising

Jupiter, Spica and the Moon in the eastern sky at 11:30 p.m. tonight March 15, 2017. Created using Stellarium.

Jupiter and moons in the evening.

Jupiter and its Moons tonight March 15, 2017 at 11:30 p.m.. I noticed Europa’s shadow was cast on the planet. It’s a bit too low in the sky to be seen here in northern Michigan, but easier to see east of here, and as it rises higher. See the table of events below. Created using Cartes du Ciel (Sky Charts).

Europa: Shadow crossing start: 16 Mar 2017 2:46 UT
Europa: Transit start: 16 Mar 2017 3:55 UT, 15 Mar 11:55 p.m. EDT
Europa: Shadow crossing end : 16 Mar 2017 5:15 UT, 1:15 a.m. EDT
Europa: Transit end : 16 Mar 2017 6:15 UT, 2:15 a.m. EDT
Satellite events were obtained from Project Pluto.

Planets and Moon at sunset and sunrise of a single night

Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on March 15, 2017. The night ends on the left with sunrise on March 16. Note that Venus is visible at both sunrise and sunset at least on these charts. It will rise only 13 minutes before the Sun, so would not actually be visible. Click on image to enlarge. Created using my LookingUp program.

Venus appears 8° 20′ north of the ecliptic (path of the Sun in the sky) now.  This is due to the fact that Venus’ orbit is slightly tilted to the Earth’s orbit by 3.3 degrees, and now it is extremely close to us at only 27 million miles (43.5 million km) from us, a lot closer than Mars ever gets to us.

03.14/2017 – Ephemeris – It’s Pi Day!

March 14, 2017 Comments off

Ephemeris for Pi Day 3.14, Tuesday, March 14th.  The Sun will rise at 7:56.  It’ll be up for 11 hours and 51 minutes, setting at 7:47.  The Moon, 2 days past full, will rise at 10:04 this evening.

Welcome to Pi Day.  I had some NASA inspired links posted on this blog this past Sunday for your enjoyment.  Also simply do an Internet search for Pi Day and lots of fun information and activities will be listed.  I remember an exercise in high school calculating pi with an inscribed polygon in a circle of ever increasing numbers of sides.  Somewhere in there I messed up and came out with an answer that didn’t quite get there.  This was in the years B.C. that is Before Calculators.  Speaking of round things, Jupiter will rise this evening followed by the Moon and the star Spica in the east.  They will all be up by 10:30.  Jupiter is not yet an evening planet, since it is not up by sunset.  It’s still seen in the morning sky.

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

Addenda

Had I known in the tenth grade this strategy to calculate pi, I could have saved myself a lot of grief.  Simply google calculate pi with toothpicks.  One of the hits was this from Science Friday:  https://sciencefriday.com/articles/estimate-pi-by-dropping-sticks/*.  Basically it’s by dropping lots of toothpicks on a piece of paper with parallel lines spaced the length of the toothpicks apart.  The total number of toothpicks dropped times two divided by the number of toothpicks that cross a line will approximate pi.  The more drops, the closer to pi one gets.

  • In the formula in the link, if the length of the toothpicks equals the distance between the lines, those terms drop out of the formula.

Grouping of Jupiter, the Moon and the star Spica

Jupiter, the Moon and the star Spica

Jupiter, the Moon and the star Spica at 11 p.m. March 14, 2016. Since the Moon moves eastward about its diameter an hour. So observers east or west of here will see the Moon in a different position in relation to these other two bodies. Created using Stellarium.

03/13/2017 – Ephemeris – More thoughts about yesterday’s time change

March 13, 2017 Comments off

Ephemeris for Monday, March 13th.  The Sun will rise at 7:58.  It’ll be up for 11 hours and 48 minutes, setting at 7:46.  The Moon, 1 day past full, will rise at 9:03 this evening.

We are now plunged back into dark mornings like we were two month’s ago thanks to the start of Daylight Saving Time.  However we are only a week from the vernal equinox, the first day of spring here in the northern hemisphere.  However some of my blog followers down under will experience the start of autumn on that day.  For us in the next three months the sunrise time will back down 2 hours, and will rise around 6 a.m.  Our sunset times will advance a bit less than that, an hour and 45 minutes.  The lopsidedness is a consequence of both the Earth’s axial tilt and its slightly elliptical orbit.  We are moving somewhat away from the Sun now and are slowing down a bit.  It’s all kind of hard to explain, but makes perfect sense… eventually.

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

Addendum

Well, I’m going to try to explain it now.

If one visits most observatories, there will be a clock, usually in the dome that doesn’t seem to read the correct time. We have one in Northwestern Michigan College’s Rogers Observatory’s dome. It only agrees with the time on your watch for an instant on October 16th. It’s called a sidereal clock and it measures Earth’s rotation with respect to the stars, and it gains approximately 4 minutes a day compared to our normal clocks which are geared to the Sun.

The Earth and all the planets orbit the Sun in a counterclockwise direction when seen from the north. Also the Earth and most of the planets spin also in a counterclockwise direction. The exceptions are Venus and Uranus. Most large satellites like our Moon also orbit their planets in a counterclockwise direction. From the surface of the Earth these bodies appear to generally move eastward, while the celestial sphere mirror reflects our eastward rotation by appearing to move east to west.

The Sun appears to move about one degree a day eastward. (360° / 365 days = 1° approximately). The Earth rotates through 15° an hour (360°/24 hours = 15° and 60 minutes in an hour / 15 = 4 minutes to rotate a degree). So on average and approximately after the Earth rotates back to the same point with regard to the stars, it has to rotate and extra degree to catch up to the Sun, which takes 4 more minutes, which is why the solar day is 4 minutes longer than a sidereal day. (Well, 3 minutes 55.9084 seconds if you want to get picky about it!)

Of course it’s not that simple. It never is that simple. This would all work out if the Earth orbited the Sun in a uniform circle and the Earth had no axial tilt. The Earth’s tilt is also called obliquity. The Sun would appear to move uniformly over the Earth’s equator. That Sun, called the mean Sun is what we base our solar time on, not the real Sun. However the Earth’s orbit is elliptical, with the Earth moving fastest at its perihelion or closest point to the Sun, around January 3rd, and slowest at aphelion or farthest point around July 4th. Also the Earth’s axial tilt is 23 ½ °, and is only on the equator two days a year March 20th and September 23rd.

Ever see this funny figure 8 in the Pacific Ocean on old globes?

The Analemma

Illustration 1. An Analemma graphically demonstrating the actual Sun’s relation to the mean Sun during the year.

Both eccentricity and obliquity work together to produce the analemma as seen in the diagram below. This figure 8 can actually be photographed in the sky by exposing the same frame of film at regular intervals, or stacking images of the same area of the sky over a year at the same time of day. There are plenty of examples using an Internet search engine to search for analemma images. It is one way to illustrate the equation of time, which is the correction one must make to a sundial reading to get to the correct local mean solar time. To that one must add or subtract one’s offset from the time zone’s time meridian. See Friday’s post.

Cause of the analemma

Illustration 2. How eccentricity of the Earth’s orbit and obliquity combine to affect the analemma. The effects add at the bottom near the winter solstice and subtract near the summer solstice.


The above diagram was taken from Ethan Siegel’s Starts with a Bang blog: http://scienceblogs.com/startswithabang/2010/12/17/celebrate-this-winter-solstice/ which also explains it.

The equation of time can be found in tabular form for easy sundial correction, or in a linear graphical form as seen below.

Equation of Time

Illustration 3. Linear representation of the equation of time

Actually the biggest effect on the equation of time, is especially near the solstices is the Earth’s obliquity (axial tilt). Below we see how the Sun’s declination affects how fast it appears time wise.

Sun crossing time lines

Illustration 4. How the Sun’s declination affects how rapidly it appears to cross time lines (meridians).

Declination of celestial objects is the same as latitude on the Earth. A star whose declination is the same value as one’s latitude will cross at the zenith once a day. In illustration 4 note that the near the solstices the time lines (meridians) are closer together, so the Sun will pass them faster than when near the equinoxes where the time lines are farther apart and the Sun is moving somewhat diagonally, taking longer to cross the time lines. In time only east-west motion counts.

Looking at Illustration 2, I’ve added arrows at the top (northern) and bottom (southern) extremities of each analemma source to give some idea of the Sun’s apparent speed at the solstices. At the bottom, near the December solstice the eccentricity speed of the Sun adds to the obliquity speed increasing the effects at that part of the analemma lobe, making it bigger. At the June solstice end of things eccentricity speed is in the opposite direction, slowing the Sun down.

So what? This affects the dates of the earliest and latest sunrises and sunsets. Here are those dates and time values for us here in northern Michigan (specifically the Interlochen/Traverse City area):

Earliest and Latest Sunrises and Sunsets

Table of Earliest and Latest Sunrises and Sunsets during the year for Interlochen/Traverse City area of Michigan.

All this may make little difference to our modern lives, governed by the atomic clocks in Paris and Fort Collins, Colorado, divorced as they are from the Earth’s actual rotation and the Sun except for the inclusion of the occasional leap second, like we had last December 31st. To folks like me who are amateur astronomers and have (or had in my case)  a day job, it would’ve been nice to have, on the summer solstice, astronomical evening twilight end before midnight.

I hope this helped rather than confused you.  What do you think?  drop me a comment.

Pi Day fun

March 12, 2017 1 comment

Tuesday is Pi Day (3.14) in American format.  I received this email from Solar System Ambassadors Headquarters about educators, students and everyone else having fun with our favorite Greek letter:

From: Orr, Kim [mailto:Kimberly.M.Orr@jpl.nasa.gov]
Sent: Friday, March 10, 2017 10:59 AM
To:
Subject: Pi Day is Live!

Hi all,

Happy Friday before Pi Day! Speaking of Pi Day, we’re now live with the following #NASAPiDayChallenge products:

We would, as always love any publicity, so please share like the wind. We’ll plan to tweet/post on early on March 14 with a link to the NASA Pi Day Challenge (https://www.jpl.nasa.gov/edu/nasapidaychallenge/). If you could retweet/repost us then, that would be great. For everything else, just be sure to use the hashtags: #PiDay and especially #NASAPiDayChallenge. Here’s a brief schedule of promotions:

  • March 10: Promo lesson and teachable moment, focusing on educators
  • March 13: Promo infographic/poster/downloadable products to general audience
  • March 14: Promo NASA Pi Day Challenge to general audience, encourage participation in share campaign
  • March 15: Ask for answers via social media
  • March 16: Promo and release answer key

You can find all the graphics and promos in my exchange (kmorr/*PI DAY 2017) should you need them. They also include some incredible gifs made by Scott Hulme (check out the Mars crater one!).

Thanks all and let me know if you have any questions!

Best,

Kim

 

Categories: NASA Tags:

03/10/2017 – Ephemeris – Daylight Saving Time starts Sunday

March 10, 2017 1 comment

Ephemeris for Friday, March 10th.  The Sun will rise at 7:03.  It’ll be up for 11 hours and 39 minutes, setting at 6:42.  The Moon, 2 days before full, will set at 6:38 tomorrow morning.

Daylight saving time will begin this Sunday at 2 a.m.  That means “spring forward”, setting our clocks ahead an hour.  Did you know that we spend more time under daylight time than standard time.  Standard time only lasts about 4 months and one week.  The rest of the time, nearly 8 months is spent under daylight time.  According to theory, anyway, one’s time meridian should run in the middle of its time zone. Right now our standard time meridian of 75 degrees west longitude runs through Philadelphia, 5 hours west of the prime meridian of Greenwich.  Come Sunday our time meridian will be 60 degrees west longitude, in the Atlantic at our latitude, and further to the north just touches the eastern tip of Nova Scotia.  In relation to the actual Sun we will be an hour and 43 minutes behind it, which is why sundials don’t tell the correct time around here.

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

Addendum

Time Zones

Time zones with their meridians for North America.

03/09/2017 – Ephemeris – More on the definition of a planet controversy

March 9, 2017 Comments off

Ephemeris for Thursday, March 9th.  The Sun will rise at 7:05.  It’ll be up for 11 hours and 35 minutes, setting at 6:41.  The Moon, 3 days before full, will set at 6:03 tomorrow morning.

Last Friday’s Weekly Space Hangout, on Google Hangouts featured Dr. Alan Stern, principal Investigator of the New Horizons Mission to Pluto and beyond.  Dr. Stern considers himself a planetary scientist, rather than an astronomer, and doesn’t much care for the IAU or International Astronomical Union’s definition of a planet.  To him and other planetary scientists: if it’s round and not a star… it’s a planet.  They’re are more concerned about what it is than where it is, or what it’s orbiting.  Planetary science encompasses geology, climatology,  chemistry, and astrobiology among others.  For instance astrobiology is looking at the origin of life on the Earth and looking for life on other worlds like the planet Mars and at least three moons, Jupiter’s Europa and Saturn’s Enceladus and Titan.

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

Addendum

Check out last Friday’s Weekly Space Hangout here

For the latest on astronomical, space events and discoveries this is a good place to go.