Moon – Mars Conjunction

   Over the next two evenings the 12-13 day old waxing gibbous Moon will pass by the ‘Red Planet’ Mars coming within about 7-8o on Wednesday October 28th and within about 3-4o on Thursday evening October 29th.

   
   
   

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Neptune at Opposition – 2020

   Friday September 11th the outer planet Neptune reaches a position in its orbit around the Sun when it is on the opposite side of the Earth from the Sun. This coincidentally is known as opposition, and it is an orbital position which only the planets further from the Sun than the Earth may reach.
   At opposition an object orbiting the Sun beyond Earth’s orbit rises and sets in a fashion similar to our Moon when it is at full phase, in that the object at opposition rises at sunset and sets at sunrise.
   Currently Neptune rises at sunset and by late evening is over the southeastern horizon. Neptune has an apparent magnitude of 7.88 so it is beyond unaided-eye visibility but could be visible with large aperture telescopes or with a camera.

   
   
   

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Venus at Western Elongation

inner-planets-positions   Wednesday August 12th the inner planet Venus reaches the point in its orbit called greatest western elongation. As this graphic shows the inner planet Venus, or Mercury, is more or less at a right angle (90o) from the Sun and Earth at western elongation. From the surface of the Earth, your backyard, for example, Venus is to the right, or western side of the Sun and is rising before the Sun.

   On the day of the elongation Venus will be very visible over the southeastern horizon at or before sunrise local time. Venus is joined by a few other planets, Jupiter, Uranus, Mars, and Dwarf Planet Ceres. The waning crescent Moon is nearly straight overhead (at least from 40oN) and a few degrees from the open star cluster the Pleiades. In this graphic the orbital path of Venus has been added, and also an arrow to show the direction Venus will now be moving toward (eastward).

   At western elongation Venus, or for that matter Mercury the other inner planet, is as far out from the Sun as we see them and as a result Venus or Mercury will rise at the earliest time for this orbit. Locally Venus rises that morning at around 3:00 am CDT. On the day of the western elongation Venus will be 45.8o from the Sun. From western elongation forward Venus or Mercury will be moving eastward toward the Sun and each day rising closer and closer to the time of sunrise. As the planet moves eastward it is moving further away from the Earth toward superior conjunction on the opposite side of the Sun.


    As the distance between the Earth and Venus, or Mercury, increases combined with the decreasing angle between the planet, the Earth, and the Sun, Venus or Mercury decreases in apparent size and also waxes through gibbous phase shapes but we never see it at a full phase since that is at superior conjunction.

   
   
   

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Moon – Mars Conjunction

   Early mornings before sunrise the waning gibbous Moon is working its way eastward toward new Moon phase. Along the way the 20-day old waning gibbous Moon will be about 1o from the ‘Red Planet’ Mars on Sunday morning August 9th . Both will fit within the field of view of binoculars and should fit within the field of view of a low-power widefield type telescope eyepiece.
   The contrast in apparent magnitude is quite a range, from the Moon’s -12.0 to the -1.22 apparent magnitude of Mars.

   
   
   

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Moon – Mars/Neptune Conjunction

   Friday June 12th and Saturday June 13th before sunrise local time look toward the eastern horizon for the waning gibbous Moon to be near the planets Mars and Neptune. On both mornings the 20-22 day old Moon will be within about 7-9o from the two planets. Depending on your binoculars all three may fit within the field of view. However given the range of apparent magnitudes the reflected sunlight from Neptune (7.88) and possibly from Mars (-0.20) will be overshadowed by the much brighter Moon’s apparent magnitude (-12.0).


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.


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Mars – Saturn Heliocentric Conjunction – 2020

   Monday June 1st two of the outer planets, Mars and Saturn, will be more or less at the same heliocentric longitude of about 280o, and would be in what is called a heliocentric conjunction. Heliocentric (Sun-centered) coordinates uses an overhead view of the solar system with planet location given as degrees of heliocentric longitude. The heliocentric longitude is based on a view from the Sun and is given as the angle between a planet and the vernal equinox. The vernal equinox, 0o, is located within the constellation of Pisces the Fishes, and is the intersection between the ecliptic and the celestial equator.
   As the Earth revolves around the Sun it ‘gives’ the Sun its apparent motion eastward along the ecliptic. When the Sun crosses the celestial equator at this intersection it is moving north. At the crossing northern hemisphere winter becomes spring – the opposite seasonal change for the southern hemisphere.

   Despite having the same heliocentric longitude, when viewed from the surface of the Earth, the two show an east to west difference of about 2 hours of right ascension.

   
   
   

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.


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Moon Mars Conjunction x2

   Thursday morning May 14th the last quarter Moon will be about 8-9o to the west from the ‘Red Planet’ Mars. The following morning, Friday May 15th the waning crescent Moon will be about 6-7o from Mars but this time on the east side.



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.


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Saturn at Western Quadrature – 2020

saturn-west-quadrature   Tuesday April 21st, the position of the planet Saturn with respect to the Earth and the Sun places this ringed planet at what is called western quadrature. Saturn is at a 90 degree angle from us as this graphic shows. Think third quarter Moon as that is a fair comparison of the relative positions. At this position Saturn leads the Sun across the sky from east to west as the Earth is rotating, meaning that Saturn rises before the Sun and also sets before the Sun.

Saturn currently is within the constellation of Sagittarius the Archer as this graphic shows. From the northern hemisphere, looking toward the southern horizon, you can find Saturn over the southeastern horizon about midway between Mars to the east, left, and Jupiter to the west, right.

Learn a little (or a lot) about Saturn by visiting the Cassini at Saturn mission web site.
Click here to go to the Cassini Mission web site.

   This is a short 5 minute video I made as part of a live musical performance called “Orbit”. This is a piece from the much longer tour of the solar system performance and video and shows Saturn and some of its moons as viewed from the Cassini spacecraft that month.

   
   
   


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.

An ‘Old’ April Moon at Apogee

   Our Moon reaches apogee, (greatest distance from Earth), for this orbit, on Monday April 20th. At that time the new Moon will be at a distance of 31.86 Earth diameters 252,563 miles (406,641 km) from the Earth.

   On the day of the apogee Moon the 27.2-day old thin waning crescent Moon will be rising about 1 hour before the Sun rises and if spotted could become a personal record for seeing an ‘old’ Moon.

   While out looking for the Moon there are several planets arranged across the southern and southeastern horizon. They are arranged west to east (or east to west) along the ecliptic, the Earth’s orbital path around the Sun, as the two graphics below are showing.

   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*

   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit” in NSTA’s Science Scope Magazine.

   
   
   
   
   
   
   
   
   

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.


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Morning Conjunctions

   This morning the 21-day old last quarter Moon was a few degrees from the outer planet Jupiter. As the Moon continues its eastward orbit, waning through the crescent phases, it will pass by Mars and Saturn, then 2 days later the waning crescent Moon will be close to the Dwarf Planet Ceres.



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.


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