Mercury at Inferior Conjunction

orbital-positions   Wednesday September 30th the innermost planet Mercury reaches inferior conjunction. At inferior conjunction Mercury will move between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.

mercury at inferior conjunction   While at this inferior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon Mercury, during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node).

   
   
   
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.

Leo with Planets, Orion and ISS

   The three morning planets this morning at 6 am CDT. Compare the separation between Mars and Regulus this morning with my pictures from 2 days ago and you can get an idea of how much Mars moves daily as it orbits the Sun.
   Camera settings were 18mm; ISO 1600; f5.0; 6 seconds.

   This morning was also special as the International Space Station was going to pass over my part of the world at about the same time. The path the ISS followed took it from the west-northwest to the southeast and it reached a brightness that outshone one of the brighter stars of Orion, Rigel, and also the brightest night time star, Sirius.
   Camera settings were 18mm; ISO 1600; f5.0; 4 seconds. This is a stacked picture using 3 separate pictures.

   
   
   
   

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.

3 Planets and the Lion

   This morning I had an opportunity to take a few pictures of Venus, Mars, and Jupiter. Next to Mars is the star Regulus, the heart of Leo the Lion. Both Mars and Regulus are about the same in apparent magnitude, and look like a pair of contrasting colored stars I was parked near MO Highway 50 near where I live and as a suburb of Kansas City there is a lot of commuter traffic heading into the city in the morning..
mars-regulus-venus-cropped   The picture was a 6-second exposure so that I could get headlight trails. Other particulars: ISO 100; f10; 18mm. Mars and Regulus were easy to see with the naked eye however they do not show that well in the picture. This is a cropped portion of a picture taken with the lens at 50mm.

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.

Leo and the Planets

   Friday morning September 25th the planet Mars will be within 1o from the star Regulus in Leo the Lion. Both shine with nearly the same apparent magnitude, Regulus (1.34) and Mars (1.78), making them look sort of like a binary system composed of a reddish star and a blue-white star. Interestingly Regulus is a multiple star system composed of at least 4 stars, with Regulus the brightest.
mars-regulus-venus-cropped   Here is a picture from that morning.
   You may also notice that there are three planets now visible in the hours before sunrise. Things will only get better with morning planet viewing as this year comes to an end. Saturn will join the group and then by the end of January Mercury will become the fifth morning planet visible. This animated graphic is set for 7:15 am local time on the 15th of each month.
Pay attention to the graphic for December. It is possible that Comet Catalina (C/2013 US10) may still be visible – that is assuming that it has brightened as predictions have suggested.

Stay tuned!

 

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.

Pluto Shifts Out Of Reverse

   Thursday September 24th the second largest of the known Dwarf Planets, Pluto, ends its apparent retrograde motion and resumes its regular direct or eastward motion in its 248 year (Earth years) long revolution around the Sun. Retrograde motion is an apparent westward, or backward motion relative to the regular eastward orbital motion nearly all solar system Sun orbiting objects follow. Any of these objects further from the Sun than the Earth seem to slow down, stop, and then reverse their direction for a period of time lasting from several days to a few weeks. The apparent reverse in direction, retrograde motion, happens as the faster moving Earth passes by the more distant object.
inner-planets   While retrograde motion is generally thought of in terms of outer planets the two inner planets, Mercury and Venus, also have retrograde motion but not as a result of the Earth’s orbital motion. From eastern elongation through inferior conjunction to western elongation these two inner planets move westward. And then from western elongation through superior conjunction to eastern elongation they move eastward.

   
   
   
   

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.

The September Equinox of 2015: BTW, The Sun Is Not In Libra

   On Wednesday September 23rd at 8:21 UT, (3:21 am 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.

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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 at its Brightest

   Have you noticed that bright shining ‘star’ in the morning skies? At this time of the year you could be thinking I am referring to Sirius, the brightest night time star. While Sirius, no kidding, has an apparent magnitude of -1.4 it is out shined by the inner planet Venus now rising about 2-3 hours before sunrise local time. Venus currently has an apparent magnitude of -4.54 and coincidentally Venus is at its greatest brilliance.

Venus monthly: January-December 2015

Venus monthly: January-December 2015

   This is not the first time that Venus has been at its greatest brightness as this point in Venus’s orbit occurs as a function of the planet’s orbital position relative to the Earth and the Sun. Venus increases in its apparent size as it moves from superior conjunction, behind the Sun through eastern elongation to inferior conjunction. During this time Venus goes through phase changes starting with a waning gibbous phase following superior conjunction to a new phase at inferior conjunction. At this point Venus is at its greatest apparent size however we will not see Venus until it moves away from inferior conjunction. As Venus moves toward western elongation and then to superior conjunction its apparent size decreases while it goes from a large crescent shape to a smaller waxing gibbous phase.
   Venus was at inferior conjunction this past August 15th so it was last at its greatest brightest on July 12th when it was a large but thin waning crescent shape. Now Venus is moving past inferior conjunction and is at a orbital position similar to the one it had in July making Venus appear at its greatest brightness.

   
   
   
   

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.

Saturn – Moon Conjunction

   Thursday evening, September 18th the 6-day old waxing crescent Moon is within 1-2o from the planet Saturn making for an interesting view through binoculars.

   
   
   
   

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.

Sun Enters Virgo

view_from_earth   Thursday September 17th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation of Leo the Lion and into the constellation of Virgo the Harvest Maiden. This is the true or actual position of the Sun as opposed to the pseudoscience of astrology which usually has the astrological Sun one constellation ahead or east from the Astronomical Sun’s position.

   In a few days the Sun, according to astrology, will cross the ecliptic moving southward crossing from Virgo into the constellation of Libra the Scales. We know this day as the September equinox, which this year is on the 23rd.

   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.
   
   
   

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.

Luna Passed an ‘Innie’

   Tuesday evening September 15th the thin 2.5-day young waxing crescent Moon will be near the bluish-white star Spica in the constellation Virgo the Harvest Maiden. Both of which, the Moon and Spica, are low over the western horizon at sunset local time. This graphic is set for just after sunset local time and shows the location of a couple of the Dwarf Planets and the innermost planet (the ‘Innie’), Mercury. What Luna passed was that on Monday evening the even thinner waxing crescent Moon was near Mercury, however from a mid-northern latitude perspective the two were low above the horizon and relatively close to the Sun making them a challenge to see.

    Mercury is actually best viewed from the southern hemisphere this month. Here is a graphic showing the same view at the same date and time however from 90o south of my location at the southern latitude of 40oS.

   
   
   

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.