See Comet PanSTARRS (C/2013 X1) in Binoculars at Dawn

An old friend from winter returns for an encore in the morning sky. Already visible in binoculars, Comet PanSTARRS (C/2013 X1) may reach naked-eye visibility in June. 

Comet with Naked-Eye Potential?

Comet PanSTARRS (C/2013 X1) from Bologna, Italy on December 12, 2015. It's currently visible in binoculars.
Adriano Valvasori

2016 hasn't been the best year for naked-eye comets. Not yet, anyway. Skywatchers have had to subsist on whatever morsels fate might send our way. Not that we've lacked in fluffy fuzzballs. There've been plenty to pick from, just few bright ones.

That's why 252P/LINEAR was literally a gift from above. This otherwise faint periodic comet underwent an outburst sometime after perihelion in March and brightened unexpectedly to magnitude +6 in April. A month later, it still remains luminous enough to see in 10×50 binoculars from dark skies.

As it fades, up-and-coming PanSTARRS (C/2013 X1) shows great promise as the next naked-eye comet. PanSTARRS X1 was discovered by the University of Hawai‘i's automated Pan-STARRS 1 (Panoramic Survey Telescope & Rapid Response System) on December 4, 2013. Back then it was a 20th-magnitude wisp. Many of us last encountered X1 in mid-February, as it crossed from Pegasus into Pisces while slowly sinking in the west. Glowing at 9th magnitude and wagging a short tail, it livened up shivery winter evenings.

Two Tails to Boot

Comet PanSTARRS X1 displays both dust (top) and ion tails in this photo taken May 5th. The comet bears a remarkable resemblance to last December's appearance of Comet Catalina.
Gerald Rhemann

Since passing perihelion on April 2nd, X1 has been slowly climbing back into the dawn sky. Because it was positioned along the Pisces–Aquarius border in negative declination territory, southern observers were the first to spot it later that month. Over the past week, an earlier rising combined with the comet's westward motion have finally pushed it high enough to clear the horizon at the start of morning twilight for mid-northern latitude observers.

Swing Low Sweet Comet

After a slow start in Aquarius, PanSTARRS X1 picks up speed as we approach the first day of summer, when the comet makes its closest approach to Earth at a distance of 59.5 million miles (95.8 million kilometers). The map shows its position every 10 days at 4 a.m. local daylight time. Click to enlarge.
Chris Marriott's SkyMap

On May 4th, Chris Wyatt in Walcha, New South Wales, Australia used 7×50 binoculars to spot X1 before dawn, describing it as magnitude +7.6 with a well-condensed, tail-less coma 8.7′ across. A Swan Band filter enhanced the view.

Water Slide Across Aquarius

This black-and-white reverse map shows the comet's path in detail with positions marked daily for 4 a.m. local daylight time for the Americas. Stars shown to magnitude +8.5. The comet is expected to brighten from +7.5 to about 6th magnitude next month when it's closest to Earth. Click to enlarge.
Christ Marriott's SkyMap

This coming week, skywatchers across the U.S. heartland (latitude 40° North) will find X1 about 10° degrees high at the cusp of dawn, low in the southeastern sky in Aquarius. Observers in the northern United States, southern Canada, and central Europe will have to reach a little deeper as the comet only climbs to an altitude of 5–7°. In the land of sweet tea and red-eye gravy, X1 stands 20° or higher before dawn and should be a snap to see with binoculars. The Moon won't be a bother until about May 18th. After that, the next dark-viewing window occurs from about June 1–15.

Plan your cometary rendezvous with care, so you can make the most of the brief window when the comet reaches maximum altitude before the light of dawn compromises the view.

I do this by taking the time of sunrise and subtracting two hours, the length of morning twilight at my latitude. That gives me the time when morning twilight begins — about 3:40 a.m. in mid-May. Since the sky is still quite dark at the start of dawn, I add in a fudge factor of about 20 minutes. That takes me to 4 a.m. Later than that and twilight might make a low-altitude object like X1 to difficult to see. Of course, the brighter the object the bigger your fudge factor can be. Click over to or the United States Naval Observatory and enter your city to find sunrise, sunset, and twilight length for any day of the year.

A Summer Solstice Peak

In this graph depicting the comet's light curve, the horizontal axis shows the date, the vertical axis, magnitude. Each dot represents an observation. Peak brightness is expected around the summer solstice.
Seiichi Yoshida

Both low altitude and lengthening twilights conspire to make sighting X1 more challenging for all except those living in the southern United States and points south in the coming weeks. Thankfully, even as the comet dips south during most of its apparition, its earlier rising will help to "brake" its declining altitude. Observers in Europe and the northern United States should be able to follow X1 into early June; further south, it will remain visible throughout the summer.

Closest approach to Earth occurs on the first day of summer in the Northern Hemisphere when the comet will presumably peak in brightness around magnitude +6, right at the edge of naked-eye visibility. On June 29th, it begins to climb north again but very slowly.

I hope you're looking forward as much as I am to finding and following this latest visitor from the Oort Cloud. In December 2015, it experienced a major outburst and brightened to magnitude +9. Might the comet have more surprises in store?

8 thoughts on “See Comet PanSTARRS (C/2013 X1) in Binoculars at Dawn

  1. Bob-PatrickBob-Patrick

    Bob King…

    Thank you for the update on Comet PanSTARRS (C/2013 X1). The images and links are invaluable.

    I particularly like Christ Marriott’s SkyMap.

    …Bob Patrick

  2. Joe StieberJoe Stieber

    I was out for a look this morning (May 14, 2016) from the relatively dark New Jersey Pinelands. Despite billowing Milky Way from overhead in the Summer Triangle down to Sagittarius, there was some fog low in the east towards the comet. Nevertheless, I was able to see C/2013 X1 (PANSTARRS) with my 16×70 binoculars just after 4 am EDT. It was just a dim patch of haze, undoubtedly suffering from the fog, but it was there. I also had my first sighting of Neptune for the season. It was only 6.5 deg from X1 near Lambda Aquarii. In fact, on the finder charts above, I suspect the “star” plotted just below and slightly right of Lambda is actually Neptune. Lambda isn’t labeled, but it’s the star in the stick figure midway between Phi and Tau Aquarii as labeled on the B&W chart, almost directly below the Water Jar.

    1. Bob KingBob King Post author

      Hi Joe,
      Reading your description gets me excited for my first attempt to see the comet tomorrow morning. You’re right – that would be Neptune, just below Lambda. It’s in a great spot for easy locating right now.

  3. Tom Hoffelderrocksnstars

    Hello Bob, as you probably don’t remember, back on March 17th, I added what most people would call a pessimistic (I prefer realistic) comment to your BA14 Flyby article, saying I didn’t expect to see 252P due to a combination of moonlight, altitude and predicted magnitude. Your hope that it didn’t do a full reverse was realized and much to my surprise (only pessimists can be pleasantly surprised), I did view 252P in my C14 just before midnight on 4/28, which means I didn’t have to get up early to see it! The magnitude then was reported to be around 7, but as soon as I saw it, I knew that had to be an integrated number. The size and brightness reminded me of M101, which has a published vis magnitude of 7.5, and a not-so-published Surface Brightness of 14.6 (mag/sq arcmin). My impression is that surface brightness is much more indicative of what will be seen with “large objects,” so much so that magnitudes are basically useless in those cases.

    1. Bob KingBob King Post author

      Hi rocknstars,
      Yes, pessimism has its positive side in that it can set us up for pleasant surprises. I’m happy 252P hung in there – I even saw it in 10×40 binoculars faintly about a week ago. As you mention, the comet was huge back in April. Estimating magnitude was much easier using binoculars compared to many telescopes simply because it was so big! Thank you for writing.

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