Mars Reaches Aphelion

mars-ani
Saturday October 7th the outer planet planet Mars will be at aphelion, its greatest distance from the Sun this time around. For this aphelion Mars will be 1.408 AU (210,633,802 km – 130,881,776 miles) from the Sun. The orbit of Mars is more elliptical than the Earth’s nearly circular shaped orbit and so it has a much wider range of aphelion and perihelion distances. Mars has an orbital eccentricity of 0.0935 compared with Earth’s 0.0167, and the length of a year on Mars is equal to 687 Earth days (1.88 Earth years).

Take a brief fly-over of Mars. Music by Dark Matter.

Caution: Objects viewed with an optical aid are further than they appear.    Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Venus – Mars Conjunction


   Thursday morning October 5th the inner planet Venus will be within about 0.5o from the planet Mars. With either a telescope or through binoculars the two planets will make for a great view.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

October Moon at Descending Node

   Monday October 2nd the waxing gibbous Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.
   

   On the day of the node crossing the 13-day old waxing gibbous Moon will be over the east-southeast horizon an hour or so after sunset local time. The Moon will be about 10o from the outermost, and 8th, planet Neptune.
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

September Moon at Apogee

   Our Moon reaches apogee, (greatest distance from Earth), on Wednesday September 27th. At that time the Moon will more or less be at a distance of 31.70 Earth diameters (404,308 km or 251,225 miles) from the Earth.

   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*

   On the day of the apogee the 7.5-day old first quarter Moon rises at mid-day and is about 10o to the east from Saturn and is just above M-8, the Lagoon Nebula. Unfortunately the reflected light from the Moon will brighten the sky enough to make seeing the Milky Way all but impossible. However with binoculars or a telescope M-8 may be seen – but not as well as when the Moon’s light is not interfering.

*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

Moon-Saturn Conjunction

   Tuesday evening September 26th the 6.5-day old waxing crescent Moon will be within about 2o from the planet Saturn.
   The two will make for an interesting view with binoculars but unfortunately the reflected light from the near first-quarter Moon will brighten the sky enough so that the glow from the Milky Way, just to the east, will be hard if not impossible to see.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

Orion Rising, but Not Before Me!

   So what do most people do if they wake up at 2:30 am on a Sunday morning and can’t get back to sleep? Since this is a day off for many it means making an effort to get back to sleep for more time sleeping or staying in bed.
   What did I do?
   I gave up, got up, and let the dogs out (yeah, that answers that question!), and while they were out doing their morning business, albeit much earlier then they normally do, I checked the skies to see if they were clear. They were so then I thought if the skies are clear and I am already up, what can I see or what could I do?
   The result this morning are two versions of using images taken during a time-lapse sequence. The two pictures below are based on a taking 1 picture every minute (3:50 am CDT to 4:52 am CDT) for 61-minutes.
   The star trails picture is of the stars of Orion, and the general area surrounding Orion, rising above the treeline on the southeast side of my backyard. In making the star trails image I purposely skipped a couple of the pictures after the first one. This makes the stars of Orion more distinctive and easier to see. Not sure about the red streak as that was only in one picture.
   As I was aiming the camera and trying settings I happened to catch a few shots of a passing airplane. It’s flashing lights and the ‘always on’ lights make a distinctive pattern. Since these images were taken sort of at the same time, or at least within a a few seconds, it was possible to stack them without showing star trails.
   Camera particulars: Canon Rebel T7i; 18mm; f/4; 4 sec.; ISO-1600

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

2017 September Equinox

   On Friday September 22nd at 20:02 UT, (3:02 pm CDT) the Sun will have reached the astronomical coordinates of 0 degrees declination and 12 hours of right ascension, or RA. This places the Sun within the boundaries of the constellation Virgo the Maiden, or as some would say, “the Sun is in Virgo.” This is the actual position of the Astronomical Sun as opposed to the pseudoscience of astrology which has the astrological Sun entering the constellation of Libra the Scales.
   Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
   Declination is the astronomical equivalent to latitude measuring from 0 degrees at the equator to 90 degrees at either pole. Right ascension, or RA, is like longitude except that there is only east RA. The globe is divided into 24 sections, and like meridians of longitude, these hour circles are 15 degrees wide at the celestial equator and taper to a ‘point’ at the north and south pole respectively. In RA the ‘hour’ circles are counted from 0 hours to 23 hours. The 0 hour circle is at the intersection of the ecliptic and the celestial equator in the constellation of Pisces the Fishes.
   In a class lesson about seasons today would be one of the two days during the year when the Sun would be described as being over the Earth’s equator. If you were at the Earth’s equator the Sun would have an altitude of 90 degrees, or straight up in your sky at your local time for midday. At that moment there would not be a shadow. However at any other latitude, north or south at midday, the Sun would be at an angle less than 90 degrees and there would be a midday shadow. (Midday is the local time when the Sun is halfway between local rising time and local setting time. At any midday the Sun is at its maximum altitude above the southern horizon in the northern hemisphere, or is at its maximum altitude above the northern horizon in the southern hemisphere.)
   What is often noted about an equinox day is the reminder that equinox means equal night as a reference to there being equal amounts of daylight, and night. Also on an equinox day the Sun would rise due east and set due west for virtually everywhere on the globe. The times for sunrise and sunset would be approximately 12 hours apart, and the rising time would be around 6 am local time, and the setting time would be around 6 pm local time.

Hola Moon doh

Hola ‘Moo’ndo! Think Globally.

   So why “September Equinox” instead of using the more familiar “Fall Equinox”. Primarily because the southern hemisphere is also changing seasons on this day however for the southern hemisphere this is the start of their spring season. Despite the opposite seasons it is somewhat of a northern hemisphere bias that traditionally we would call this day the “Autumnal or Fall Equinox”, and in March we would say the “Spring” or “Vernal Equinox”. I favor the use of the name of the month so that regardless of which hemisphere it is just simply the March equinox or the September equinox, and by extension we would also have the June solstice and the December solstice..
   
   This short video shows students at Colegio Menor San Francisco de Quito, a school in Quito Ecuador, measuring the altitude of the sun hourly on the day of the 2004 September Equinox. They were taking part in Project SunShIP, Sun Shadow Investigation Project. There are also some pictures showing a local midday shadow from other participating schools in the United States and U.K.

   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.