Mars And Moon Are Mates Tonight / Binocular Comet Eludes The Lion’s Bite

Mars is in conjunction with the moon tonight. Watch for the pair during early evening hours. For U.S. observers the two will be separated by about four moon diameters. Stellarium

As twilight gives way to darkness tonight, look up at the waxing moon in the south. Just above it you’ll see the planet Mars. If you’re game, whip out a pair of binoculars and see if you can spot Mars before sunset using the moon as guide.

It’s been two months now since Mars made its most recent closest approach to Earth. While the planet has faded a full magnitude and shrunk in size since opposition, it will remain the brightest ‘star’ in the evening sky until June 27, when Arcturus will outshine it by a hair.

Mars has resumed its normal eastward motion across the sky and is now on the move across Virgo. Watch for it to glide above bright Spica in mid-July and below Saturn in late August.

Mars looks very much out of round this month. It’s only about 90% illuminated and in gibbous phase. Outer planets – especially Mars – show a gibbous phase when illuminated by the sun from a very different angle than we see it on Earth. Credit: Giorgio Rizzarelli

Through a telescope it’s easy to see that its phase has changed from full to gibbous.

The inner planets Venus and Mercury show phases from crescent to half to full as they alternatively pass between Earth and sun, but the outer planets are limited to full and gibbous phases because they’re forever outside the orbit of our own planet. No passing between the sun and Earth for them.

Left: Inner planets Venus and Mercury pass through all phases from crescent to full. Outer planets appear full around opposition and gibbous when viewed from the side. The effect is most extreme at quadrature when a planet is 90 degrees from the sun. Credit: Univ. of Tennessee-Knoxville

Full phases happens around the time of opposition when Earth and an outer planet like Mars are lined up on the same side of the sun and nearest each other. We face the planet square-on and it appears fully illuminated. Several months past opposition, sunlight strikes Mars at a very different angle than what we see on Earth. We look ‘off to one side’ instead of directly at the planet; from our perspective a portion of its globe is hidden in shadow and we see it as little gibbous ‘egg’.

The shadowing effect is most extreme at ‘quadrature’ when an outer planet lies 90 degrees from the sun, ie. it’s due south at sunrise or sunset. Mars reaches eastern quadrature on July 19.

Jupiter and Saturn also show a phase effect but it’s very, very slight because they’re so far away that Earth and sun appear in nearly the same direction from their perspective. There’s very little ‘looking off to one side’ perspective compared to much closer Mars.

8th magnitude comet K1 PANSTARRS travels above the head of Leo the Lion this month. This map shows its position every 5 days with stars to magnitude 8. The stars marked Mu and Lambda are two of the bear’s claws in Ursa Major. Leo is mid-way up in the southwestern sky at nightfall. Click to enlarge. Created with Chris Marriott’s SkyMap software

Although the moon is getting brighter by the night as it approaches full phase on June 13, I see it’s time for a new map showing the ramblings of comet C/2012 K1 PANSTARRS. This reliable comet has been slowly getting brighter all spring and now has a nice 1/2-degree tail visible in 6-inch and larger telescopes. At magnitude +8, I’ve seen it plainly with 40mm binoculars from a dark sky.

Comet K1 PANSTARRS on June 1, 2014 displays a bright head and two tails – a brighter dust tail pointing east and a faint gas or ion tail. Credit: Gianluca Masi

This month it moves from the obscure constellation Leo Minor into Leo the Lion and will continue to slowly brighten. The best time to view K1 PANSTARRS is at nightfall when it’s highest in the southwestern sky.

Moonlight won’t interfere too much with viewing tonight but will be an issue in the coming nights. Dark skies return around June 15.

Give it a try – we’ve got until mid-July. After that northern hemisphere observers won’t see the comet again until morning twilight in early September.

15 Responses

  1. Mahdi

    Is it possible to predict occultations with Chris Marriott’s SkyMap?
    And another question, Why the software has errors in predicting events both in time and angles?
    I heard the SkyMap is the most accurate in calculating events, but when I compare it to Starry Night pro plus 6, there are always difference between them.I checked events with a reliable source and what the Starry Night shown was more accurate.
    Is it something wrong with me? Should I download some files to update the SkyMap?

    1. astrobob

      SkyMap and Guide are the most accurate mapping tools I’ve used. I’m not familiar with Starry Night Pro but it looks like a wonderful program. I’ve found that SkyMap does a great job with lunar occultations but to be honest I haven’t tried it on asteroidal occultations. Those require regular updating of asteroid data files. If your files are months or a year out of date, time and angles will be different. Always use the most recent files for both asteroids and comets available at:

      I update the brighter asteroids routinely and their positions in the star fields have been dead on. Same for the planets.

  2. Giorgio Rizzarelli

    Very nice indeed the Mars-Moon conjunction today. I saw it also at sunset, when I used the Moon as a guide to find Mars in binoculars 🙂

    1. 1:45 am. slight calm after 45 mins of intense displays with lots of red showing even in my semi-urban location. Hoping to catch another burst before dawn. At my location of 49.5 N Lat., that should happen around 2:45 am.

  3. Mahdi

    Asteroids and comets databases are up to date.
    Comets and asteroids events are Ok. The problem is with planetary events! The events which SkyMap finds are similar to real events but have big errors for example 3 degrees or 8 hours difference.
    Do you know where is the problem?
    I think planets orbit data shouldn’t have error at all.
    Can you tell me how to use lunar occultation prediction tool in SkyMap? where is it?

    1. astrobob

      Those are huge errors with the planets. Like you said, that shouldn’t happen. Can you give me an example that’s wrong so I can try it with my version of SkyMap? Be sure to send me your lat. and long. I don’t think there is any kind of lunar occultation tool in SkyMap. I find the time of an occultation from other sources and then zoom in to enlarge and note the moon’s changing position minute by minute by clicking the time arrow.

  4. Michael Sangster

    Mars liked pretty good last night at 328x.

    I had my scope setup at Canal Park – almost everyone that looked at Mars could see the North Polar Cap and Syrtis Major. They also liked that Mars was visible next to the Moon without any optical aid.

    The club had scopes setup to view Jupiter, the Moon, Saturn and Mars. We also saw the space station.

    1. astrobob

      Sounds like a very good time indeed! In case you didn’t know, the white ‘cap’ right touching the broad end of Syrtis Major is Hellas – it’s covered in frost and winter clouds and looks exactly like a polar cap. It’s even bigger and more obvious than the NPC right now.

      1. Michael Sangster


        I did notice Hellas – but wasn’t sure if I was seeing frost or clouds or both. Several people did comment on a “white spot on the bottom of Mars”.

        1. astrobob

          Probably both. I almost came down but my wife and I watched a movie and then it got mostly cloudy. Glad you guys went and shared the sky.

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