Skywatching Archives

March 10, 2017March 12, 2017 by David Dickinson

Comet Encke Reemerges in the Dawn Sky

Comet 2P Encke glides through Pisces on February 16th. Image credit and copyright: Hisayoshi Kato.

Miss out on Comet 45/P Honda-Mrkos-Padadušáková last month? We’ll admit, it was fairly underwhelming in binoculars… but fear not, there are several other binocular comets in the pipeline for 2017.

Maybe you managed to catch sight of periodic Comet 2P Encke in late February after sunset before it disappeared into the Sun’s glare. Pronounced (En-Key), the comet actually passes through the field of view of the joint NASA/ESA Solar Heliospheric Observatory’s (SOHO) LASCO C3 camera from March 8^th to March 14^th before reemerging in the dawn sky.

I see you… Comet 2P Encke is now in SOHO’s LASCO C3 field of view, above Mercury (the bright object) moving in the opposite direction: pic.twitter.com/gcYwv0Sdkp

— Dave Dickinson (@Astroguyz) March 10, 2017

Northern hemisphere observers have already got a sneak peek at Encke’s performance low in the dusk in February as it heads towards perihelion. Now the comet heads southward, as it vaults up into the dawn sky for folks south of latitude 30 degrees north in mid-March. From latitude 30 degrees north, Encke will clear 15 degrees elevation above the southeastern horizon around March 31^st. Viewers south of the equator will have a much better viewing prospect, as Encke glides southward through Aquarius. When will you first spot it?

The dawn path of 2P Encke through the first week of April as seen from latitude 30 degrees north. Credit: Starry Night.

Also: don’t forget to ‘spring forward’ to Daylight Saving Time this weekend for a majority of North America prior to beginning your dawn comet vigil… Europe and the United Kingdom gets a brief reprieve ’til March 26th.

Her are some upcoming key events for Comet 2P Encke:

Closest to Sun: March 10^th, with a perihelion of 0.33 AU.

Closest to Earth: March 12^th, at 0.65 AU distant.

Brightest: Around March 15. Encke is currently at magnitude +7, and should top out at magnitude +6, though it’ll only be 14 degrees from the Sun on this date.

The projected light curve for comet 2P Encke. Image credit: Seiichi Yoshida’s *Weekly Information About Bright Comets*.

Next good apparition: 0.4 AU from Earth in 2036.

This is Encke’s 63rd passage through the solar system since Pierre Méchain linked successive passages of the comet to the same in 1819. Like Edmond Halley, Encke didn’t discover the most famous of comets that now bears his name, but instead merely deduced its periodic nature. Halley was 1^st, and Encke was second (hence the “2” in 2P…) The shortest short period comet, Encke was captured sometime thousands of years ago into its short period orbit, and is destined to burn out one day as it ventures from 4.1 to 0.33 AU from the Sun. Encke is also the source of the annual Taurid meteor shower in November, notable for producing a high rate of fireballs.

Comet 2P Encke on February 19th. Image credit and copyright: Cajun Astro.

Comets can be elusive beasties, as all of that precious quoted magnitude is smeared out over an extended surface area. Add on top this the fact that comets are also notorious for often under- and occasionally over-performing expectations. Just look at the ‘none more black’ albedo of comet 67P Churumov-Gerasimenko chronicled by ESA’s Rosetta spacecraft: it’s a miracle we can see ’em at all. And finally, that low contrast dawn sky can easily hide a faint binocular comet, fading it to invisibility. Start your comet vigil early, sweeping the horizon with binocs. An early start and a clear view are key. The slim waning crescent Moon sits 12 degrees north of Comet Encke on the morning of March 26^th, and the comet also passes less than 3 degrees from the Helix Nebula (NGC 7293) on (no joke) April Fool’s Day April 1^st.

The view on the morning of March 26th, 30 minutes before sunrise. Credit: Stellarium.

Flashback to one Encke orbit ago to 2013 and the comet provided a good dawn preshow to that biggest of cosmic let downs, Comet ISON. And although Encke makes its rounds every 3.3 years, orbital geometry assures that we won’t get another favorable viewing from Earth until 2036.

Speaking of great comets that never were, we juuuust missed having a spectacular comet this past month, when recently discovered long-period Comet 2017 E1 Borisov passes just 0.045 AU (!) interior to our orbit. Unfortunately, this occurs five months too early, with the Earth almost exactly at the wrong place in its orbit. Now, if it was only August…

Comet Teaser for 2017

Yeah, the gambler’s fallacy would tell us that we’re due for the next great comet of the century, for sure. In the meantime, we’ve still got Comets 41P/Tuttle-Giacobini-Kresák (late March/April), C/2015 ER61 PanSTARRS (May), and C/2015 V2 Johnson (June) on tap as good binocular comets in 2017.

Be sure to enjoy elusive comet Encke as it flits once more though the dawn skies.

-Read about comets, occultations, eclipses and more for the year, in our new free e-book 101 Astronomical Events for 2017 out from Universe Today.

March 3, 2017 by David Dickinson

Catch ‘The Great American Occultation’ of Aldebaran Saturday Night

The Moon nearing Aldebaran on February 5th, 2017. Image credit and copyright: Chris Lyons.

Ever watch the Moon cover up a star? There’s a great chance to see just such an event this coming weekend, when the waxing gibbous Moon occults (passes in front of) the bright star Aldebaran for much of North America on Saturday night, March 4th.

Shining at magnitude +0.85, Aldebaran is the brightest star that lies along the Moon’s path in the current epoch, and is one of four +1^st magnitude stars that the Moon can occult. The other three are Regulus, Antares and Spica. This is the 29th in a series of 49 occultations of Aldebaran worldwide spanning from January 29^th, 2015 to September 3^rd, 2018, meaning Aldebaran hides behind the Moon once every lunation as it crosses through the constellation Taurus and the Hyades open star cluster in 2017. Like eclipses belonging to the same saros cycle, successive occultations of bright stars shift westward by about 120 degrees westward longitude and slowly drift to the north. Europe saw last month’s occultation of Aldebaran, and Asia is up next month on April 1st.

The occultation footprint for Saturday night’s event. Credit: Occult 4.2 software.

All of the contiguous ‘lower 48 states’ except northern New England see Saturday night’s occultation, and under dark skies, to boot. It’s a close miss for Canada. Mexico, central America and the Caribbean will also witness the event under dark skies. Hawaii will see the event under daytime skies. We can attest that this is indeed possible using binocs or a telescope, as we caught Aldebaran near the daytime Moon during last month’s event.

Occultations give us a chance to see a split second magic act, in a Universe that often unfolds over eons and epochs. The motion you’re seeing is mostly that of the Moon, and to a lesser extent, that of the Earth as the star abruptly ‘winks out’.

Observers in northern tier states might witness an additional spectacle, as Aldebaran grazes the northern limb of the Moon. This can make for an unforgettable sight, as the star successively winks in at out from behind lunar peaks and valleys. The graze line for Saturday night follows the U.S./Canadian border from Washington state, Idaho and Montana, then transects North Dakota, Minnesota just below Duluth and northern Wisconsin, Michigan and New York and Connecticut. Brad Timerson over at the international Occultation Timing Association has a good page set up for the circumstances for the grazing event, and the IOTA has a page detailing ingress (start) and egress times for the event for specific cities.

The northern limit grazeline for Saturday night’s occultation. Credit: USAF/Wikimedia Commons/Dave Dickinson

You’ll be able to see the occultation of Aldebaran with the unaided eye, no telescope over binocular needed, though it will be fun to follow along with optics as well. The ingress along the leading dark limb of the Moon is always more dramatic, while reemergence on the bright limb is a more subtle affair.

The path of the occultation for select cities. Credit: Stellarium.

A simple video aimed afocally through a telescope eyepiece can easily capture the event. We like to run WWV radio on AM shortwave in the background while video recording so as to get a good time hack of the event on audio. Finally, set up early, watch those battery levels in the frigid March night, and be sure to balance out your exposure times to capture both Aldebaran and the dazzling limb of the Moon.

Can you see it? The Moon paired with Aldebaran on February 5th. Image credit and copyright: Lucca Ruggiero.

Anyone Live-casting the event? It’ll be a tough one low to the horizon here in central Florida, but a livestream would certainly be possible for folks westward with Aldebaran and the Moon high in the sky. Let us know of any planned webcasts, and we’ll promote accordingly.

The Moon also occults several other bright stars this week, leading up to an occultation of Regulus on March 10^th favoring the southern Atlantic. Read all about occultations, eclipses, comets and more in our free e-book, 101 Astronomical Events for 2017 from Universe Today.

Don’t miss Saturday night’s stunning occultation, and let us know of your tales of astronomical tribulation and triumph.

-Send those astro-images in to Universe Today’s Flickr forum, and you might just see ’em featured here in a future article.

February 28, 2017February 28, 2017 by David Dickinson

Join the Eclipse MegaMovie 2017 Chronicling the August Total Solar Eclipse

Eclipse Diamond Ring — The November 2012 total solar eclipse as seen from Australia. Image credit and copyright: Alan Dyer.

Ready for the “Great American Eclipse?” We’re now less than six months out from the long-anticipated total solar eclipse spanning the contiguous United States from coast-to-coast. And while folks are scrambling to make last minute plans to stand in the path of totality on Monday, August 21^st 2017, a unique project named the Eclipse Megamovie 2017 seeks seeks to document the view across the entire path.

The Project: Sponsored by Google’s Making & Science Initiative and led by Scott McIntosh from the National Center for Atmospheric Research’s High Altitude Observatory and Hugh Hudson from the University of California at Berkeley, the Eclipse Megamovie Project seeks to recruit 1,500 observers stationed across the eclipse path from Oregon to South Carolina. Although individual observers will only experience a maximum totality length of 2 minutes and 40 seconds, the complete span of the Eclipse Megamovie will last 90 minutes, compiled using observer images from coast-to-coast.

Mega movie — Getting ready for the Eclipse Megamovie project. Credit: Eclipse Megamovie Project.

“The movie is a tool for scientific exploration,” Hudson said in a recent University of California at Berkeley press release. “We’ll be collecting this level of data for the first time, from millions of observers, and it will be a valuable archive. But we don’t know what we’ll see or what we’ll learn about the interactions between the chromosphere and the corona.”

One portion of the project will have trained volunteers image the Sun from along the eclipse path using DSLRs, while another portion of the project will feature smartphone users imaging totality using a forthcoming Eclipse Megamovie app for a full length lower resolution movie.

Bikers and Baily’s Beads

The only total solar eclipse for 2017, totality for this eclipse occurs along a 114 kilometer-wide path touching on 12 states. Millions live within an easy day drive of the eclipse path, so expect lots of general public interest leading up to eclipse day. August is RV and camping season, so expect camplots to fill up quickly as well. The eclipse also occurs just over a week after the annual Biker’s Rally in Sturgis, South Dakota, affording motorcyclists a chance to stand in the shadow of the Moon en route to the annual pilgrimage.

Great American Eclipse — The path of the August 21st, 2017 eclipse across the United States. Credit: Michael Zeiler/Eclipse-Maps.

The last total solar eclipse to cross one of the 50 United States graced Hawaii on July 11^th, 1991, and the last time the umbra of the Moon touched down over the lower 48 states was on February 26^th, 1979 across the United States northwest. But you have to go all the way back over almost a century ago to June 8^th, 1918 to find an eclipse featuring totality which exclusively spanned the United States from sea to shining sea.

Observers have chased after the umbra seeking to extend fleeting totality before. Eclipse chasers documented the January 24^th, 1925 eclipse from aloft aboard a dirigible over New York City. On June 30^th, 1973, a supersonic Concorde flight chased the umbra of the Moon across northern Africa, extending totality out to 74 minutes.

The team was also on hand to perform a dry run test of the Megamovie Project at this past weekend’s annular eclipse which crossed South America, the Southern Atlantic and Africa and reports that the field test of the promised project app by Mark Bender worked admirably, and the Eclipse Megamovie App should be available to the general public soon.

Baily's Beads — A mosaic of the 2016 total solar eclipse, depicting the evolution of Baily’s Beads before and after totality. Image credit and copyright: Steed Joy.

What sort of science can such a project offer? What is left to learn from a total solar eclipse after centuries of scientific study? Well, some of the most accurate measurements of the solar diameter and the size and shape of the Sun have been made during solar eclipses. A long movie may also reveal streamers and development of the solar corona, the ethereal pearly white glowing outer atmosphere surrounding the Sun. About half as bright as a Full Moon, we only get a brief glimpse of the corona during totality. Also, the Eclipse Megamovie will get another shot at the project in April 2024, when another eclipse crosses the United States from Texas to Maine.

The Eclipse Megamovie is taking volunteers now. The gear setup required is simple, and you might have what’s needed to image the eclipse laying around already.

You’ll need a DSLR camera with a sturdy tripod, a zoom or fixed lens of 300mm focal length or better, and an ability to nail down your GPS location and the time to the nearest second. Once the volunteers are selected, training will be provided to include GPS and time stamping images, flat-fielding and more.

Phone apps will readily supply the GPS part. For time, I’d go with with WWV Radio, which broadcasts a continuous audio time hack out of Fort Collins, Colorado. This is in Universal Time, and has an accuracy of better than a second better than online time sources, which occasionally lag due to spurious web connections.

Keep in mind, you’ll be photographing the eclipsed Sun during very brief moments of totality. You’ll need to have approved solar glasses and filters in place during all partial phases leading up to and immediately after the eclipse. The Eclipse Megamovie project also hopes to catch sight of the Bailey’s Beads phenomenon as final streamers of sunlight pour through the lunar valleys, giving the illusion known as the Diamond Ring effect.

TSE2017 — An animation of the August 21st, 2017 total solar eclipse. A.T. Sinclair/NASA/GSFC

And us? We’ll be casting our hubris at the Universe and catch the eclipse from Columbia, South Carolina. We’re heeding the advice of veteran eclipse chasers, and simply enjoying our first eclipse, and imaging our second, though we may sneak in a few shots for the Eclipse Megamovie project. Universe Today publisher Fraser Cain and astronomer and AstronomyCast host Pamela Gay will lead a group watching from southern Illinois, and we’ve also heard from many other observers from around the world who’ll be visiting the U.S. the August… where will you be?

And we’ve already got a spot picked out for 2024, as the next total solar eclipse crosses Aroostook County and our hometown of Mapleton, Maine… hey, you can never start planning too early, right?

Get set for an eclipse for the ages, and be sure to contribute to the Eclipse Megamovie Project.

-Read about all eclipses, comets, occultations and more for the year in our guide to 101 Astronomical Events for 2017, free from Universe Today.

-Eclipse… science fiction? Check out our original eclipse-fueled sci-fi tales Exeligmos, Shadowfall, the Syzygy Gambit, Peak Season and more.

February 23, 2017February 24, 2017 by David Dickinson

Ring of Fire: Catch the Only Annular Solar Eclipse of 2017 This Sunday

The May 2012 annular eclipse. Image credit and copyright: Kevin Baird.

‘Tis the season… eclipse season that is, as a spectacular “ring of fire” annular solar eclipse marks the end of the first of two eclipse cycles for 2017. And although the annular path for this eclipse passes through some sparsely populated parts of the southern hemisphere, we just might get some amazing live views, courtesy of modern technology and some intrepid observers willing to adventurously trek after the shadow of the Moon.

Unlike many of the uncertainties in life, eclipses are sure to happen, a certainty ordained by orbital mechanics. Well, okay, the Vogons could always blow the Moon to smithereens this fine Thursday afternoon… but otherwise, we’re in for a true celestial show.

Eclipse circumstances: Prospects and prognostications.

The eclipse begins far out in the South Pacific at sunrise, and the path of annularity makes first landfall along the southern coast of Chile at 13:31 Universal Time (UT). The eclipse antumbra then races eastward over Argentina at 2.5 kilometers per second, as the “ring of fire” heads out over the South Atlantic where it reaches “maximum annularity” of just 44 seconds 900 kilometers southeast of Brazil. Finally, the 30 kilometer wide path touches down over Angola, nicks Zambia and ends at sunset over a southern track along the Democratic Republic of the Congo. The eclipse is partial across southern portion of South America, the Falkland Islands a swath of Antarctica and southwestern Africa.

2017 Annular Eclipse — The aspects of the February 26th, 2017 annular eclipse. Credit: F.Espenak/NASA/GSFC

Here are the partial prospects for select cities:

City – Maximum obscuration – Time

La Paz, Bolivia – 5% – 13:37 UT

Buenos Aires – 67% – 13:53 UT

The Falkland Islands – 71% – 13:56 UT

Palmer Station, Antarctica – 31% – 14:01 UT

Cape Town, South Africa – 41% – 15:59 UT

Luanda, Angola – 83% – 16:32 UT

eclipse animation — An animation of Sunday’s eclipse. Credit: NASA/GSFC/A.T. Sinclair

Annular vs. Total

Sunday’s eclipse is the first of two solar eclipses for 2017, and the only annular eclipse for the year. We get an annular eclipse when the Moon is near apogee (which occurred eight days ago on February 18^th) and the Earth is near perihelion (which occurred last month on January 4th). At this time, the apparent size of the Moon is too small to cover the Sun as seen from the Earth, resulting instead in a brilliant annulus or “ring of fire” in the sky. Likewise, we refer to the shadow trace of this ring across the Earth as an antumbra, instead of the familiar umbra of a total solar eclipse.

Strange as it may seem, annular eclipses are slightly more common than total solar eclipses in our current epoch, and will become increasingly more so as the Moon slowly recedes from the Earth.

Observing and Eclipse Safety

Unlike a total solar eclipse, safety precautions must be taken during all phases of an annular solar eclipse. We witnessed the 1994 annular eclipse from the shores of Lake Erie, and can attest that 1% of the Sun is still pretty darn bright. Use only telescope and camera filters or glasses designed specifically for solar observing, even during the annular phase. Venus should also be a splendid sight for those observing near sunset from Africa, as the Cytherian world shines at -4.3 magnitude 34 degrees east of the Sun. Viewers in southwestern African nations will also be treated to a setting Sun during the eclipse, affording the chance to include the spectacle in shots along with foreground objects on the local horizon if skies are clear.

Sun Venus Annular — The eclipse versus Venus as seen from the path through Angola. Credit: Stellarium.

Clouded out? Live on the wrong part of the planet? There are actually several options to watch the eclipse live:

the venerable SLOOH plans to webcast the eclipse.

Time and Date will provide a webcast starting at 12:05 UT from Angola:

Watch this space: we’ll be dropping in more live webcasts of the eclipse as they turn up.

Update: VTR Chile may provide a live broadcast come eclipse time.

Plan on doing an ad hoc webcast of Sunday’s eclipse from anywhere along the annular or partial track? Let us know!

Sunspot activity is currently at a lull, and the Earthward face of Sol may well be blank come eclipse day. At an eclipse magnitude of 99.22%, this eclipse juuuusst misses being a hybrid/total. It’s also possible to catch the brief flashes of Bailey’s Beads along the edge of the antumbral graze line.

Tales of the Saros

This eclipse is member 29 of 71 for saros cycle 140, stretching all the way back to April 16^th, 1512 and running out to June 1^st, 2774. If you caught the February 16^th, 1999 annular eclipse from the Australian Outback, then you witnessed the last eclipse in saros 140. Stick around until March 9^th, 2035 and you can then complete an exeligmos or triple saros cycle, joining an elite club of eclipse-chasing adventurers, indeed.

Eclipses occur in pairs or sometimes triplets, when the nodes where the Moon’s orbit intersect the position of the Sun and the Earth’s shadow along the ecliptic plane. These nodes move due to orbital precession of the Moon’s path around the Earth. If the Moon weren’t inclined relative to the ecliptic, we’d see a lunar and solar eclipse every synodic month. The February 11th penumbral eclipse ushered in the current eclipse season, which ends with this weekend’s annular eclipse.

The penumbral eclipse from earlier this month, ushering in eclipse season 1 of 2 for 2017. Credit and Copyright: Rob Sparks.

ISS and Views from Space (-ace -ace) Prospects

There is an ISS transit over SW Africa at around 15:45 UT, offering a chance to catch a transit of the station across the partially eclipsed Sun. Sun observing spacecraft in low Earth orbit including Hinode and Proba-2 also usually get good views of the eclipse.

New Moon sightings: And for the rest of the world, the hunt will be on to recover the slim waxing crescent Moon post-eclipse on the evening of Monday, February 27th. This lunation, first sighting opportunity without optical assistance favors southeast Asia.

Then, its on to eclipse season number two, featuring a partial lunar eclipse on August 7th, and then the big ticket event: the total eclipse of the Sun spanning the contiguous United States from coast to coast. Umbraphiles have been planning for this one and its brief 160 seconds maximum of totality for well over a decade now, no lie. Where will YOU be?

-Send those eclipse pics in to Universe Today Flickr.

-Read more about eclipses, occultations, comets and more for the year in our free e-book: 101 Astronomical Events for 2017.

-Eclipse science fiction? Read our original sci-fi tales Exeligmos, The Syzygy Gambit, Peak Season and more.

February 9, 2017February 9, 2017 by David Dickinson

Watch the Moon Make a Pass at Earth’s Shadow, Then Kiss Regulus This Valentine’s Weekend

Regulus Occultion — The Moon occults Regulus of January 15th, 2017. Image credit and copyright: Lucca Ruggiero

In the southern hemisphere this weekend in the ‘Land of Oz?’ Are you missing out on the passage of Comet 45/P Honda-Mrkos-Pajdušáková, and the penumbral lunar eclipse? Fear not, there’s an astronomical event designed just for you, as the Moon occults (passes in front of) the bright star Regulus on the evening of Saturday, January 11th.

The entire event is custom made for the continent of Australia and New Zealand, occurring under dark skies. Now for the bad news: the waning gibbous Moon will be less than 14 hours past Full during the event, meaning that the ingress (disappearance) of Regulus will occur along its bright leading limb and egress (reappearance) will occur on the dark limb. We prefer occultations during waxing phase, as the star winks out on the dark limb and seems to slowly fade back in on the bright limb.

The footprint for the February 11th occultation of Regulus by the Moon. Image credit: Occult 4.2 software

The International Occultation Timing Association has a complete list of precise ingress/egress times for cities located across the continent. An especially interesting region to catch the event lies along the northern graze line across the sparsely populated Cape York peninsula, just north of Cairns.

The northern grazeline for the February 11th occultation of Regulus by the Moon. Graphic by author.

The Moon occults Aldebaran and then Regulus six days later during every lunation in 2017. This is occultation number three in a cycle of 19 running from December 18, 2016 to April 24, 2018. The Moon occults Regulus 214 times in the 21st century, and Regulus is currently the closest bright star to the ecliptic plane, just 27′ away.

We’ve also got a very special event just under 14 hours prior, as a penumbral lunar eclipse occurs, visible on all continents… except Australia. Mid-eclipse occurs at 00:45 Universal Time (UT, Saturday morning on February 11^th), or 7:45 PM Eastern Standard Time (EST) on the evening of Friday, February 10th, when observers may note a dusky shading on the northern limb of the Moon as the Moon just misses passing through the dark edge of the Earth’s inner umbral shadow. Regulus will sit less than seven degrees off of the lunar limb at mid-eclipse Friday night.

How often does an eclipsed Moon occult a bright star? Well, stick around until over four centuries from now on February 22nd, 2445, and observers based around the Indian Ocean region can watch just such an event, as the eclipsed Moon also occults Regulus. Let’s see, I should have my consciousness downloaded into my second android body by then…

A graphic study of the simultaneous lunar eclipse and occultation of Regulus in 2445. Credit: NASA/GSFC/Fred Espenak/Occult 4.2/Stellarium.

We’ll be streaming the Friday night eclipse live from Astroguyz HQ here in Spring Hill, Florida starting at 7:30 PM EST/00:30 UT, wifi-willing. Astronomer Gianluca Masi of the Virtual Telescope Project will also carry the eclipse live starting at 22:15 UT on the night of Friday, February 10th.

This eclipse also marks the start of eclipse season one of two, which climaxes with an annular eclipse crossing southern Africa and South America on February 26th. The second and final eclipse season of 2017 starts with a partial lunar eclipse on August 7th, which sets us up for the Great American Eclipse crossing the United States from coast to coast on August 21st, 2017.

A lunar occultation of Regulus also provides a shot at a unique scientific opportunity. Spectroscopic measurements suggest that the primary main sequence star possesses a small white dwarf companion, a partner which has never been directly observed. This unseen white dwarf may – depending on the unknown orientation of its orbit – make a brief appearance during ingress or egress for a fleeting split second, when the dark limb of the Moon has covered dazzling Regulus. High speed video might just nab a double step occlusion, as the white dwarf companion is probably about 10,000 times fainter than Regulus at magnitude +11 at the very brightest. Regulus is located 79 light years distant.

Our best results for capturing an occultation of a star or planet by the Moon have always been with a video camera aimed straight through our 8” Schmidt-Cassegrain telescope. The trick is always to keep the star visible in the frame near the brilliant Full Moon. Cropping the Moon out of the field as much as possible can help somewhat. Set up early, to work the bugs out of focusing, alignment, etc. We also run WWV radio in the background for an audible time hack on the video.

The January 15th, 2017 occultation of Regulus by the Moon. Image credit and copyright: Lucca Ruggiero.

The best occultation of Regulus by the Moon for North America in 2017 occurs on October 15th, when the Moon is at waning crescent phase. Unfortunately, the occultation of Regulus by asteroid 163 Erigone back in 2014 was clouded out, though the planet Venus occults the star on October 1^st, 2044. Let’s see, by then I’ll be…

Comets and eclipses and occultations, oh my. It’s a busy weekend for observational astronomy, for sure. Consider it an early Valentine’s Day weekend gift from the Universe.

Webcasting the eclipse or the occultation this weekend? Let us know, and send those images of either event to Universe Today’s Flickr forum.

Read about eclipses, occultations and more tales of astronomy in our yearly guide 101 Astronomical Events For 2017, free from Universe Today.

February 7, 2017February 7, 2017 by David Dickinson

Watch Comet 45P Honda-Mrkos-Pajdušáková Fly Past Earth This Week

A recent image of Comet 45P from February 4th. Image credit and copyright: Hisayoshi Kato.

Hankering for some cometary action? An interplanetary interloper pays us a visit this weekend, sliding swiftly through the pre-dawn northern hemisphere sky.

If you’ve never caught sight of periodic comet 45/P Honda-Mrkos-Pajdušáková, this week is a good time to try. Currently shining at magnitude +6.5, the comet makes a close 0.08 AU (7.4 million miles or 12.3 million kilometers) pass near the Earth on Saturday, February 11, at 14:44 Universal Time (UT) or 9:44 AM Eastern Standard Time. This is the closest passage of the comet for the remainder of this century, and with the Moon also reaching Full this weekend, the time to track down this comet is now.

The path of Comet 45/P through Monday, February 13th. Credit: Starry Night Edu.

We wrote about the first act for this comet last December, and Bob King also wrote up a preview last month. The comet passed perihelion 0.53 AU (49.3 million miles/ 82.1 million kilometers) from the Sun on New Year’s Eve 2016, reemerging into the dawn sky. It’s now on a swift sprint through the constellation Ophiuchus, and will cross Hercules at closest approach and into Corona Borealis and Boötes in just one week. At its closest, it’ll be moving at a whooping 23 arc minutes per hour, about three-quarters the diameter of a Full Moon!

The position of Comet 45/P as seen from latitude 30 degrees north at 4 AM. Credit: Stellarium.

At closest approach, the comet may just top naked eye brightness under dark skies at +6 magnitude.

Independently discovered by three observers worldwide in late 1948, Comet 45/P Honda-Mrkos-Pajdušáková orbits the Sun once every 5.25 years. The cumbersome name is often abbreviated as “Comet 45P HMP” or sometimes simply “Comet 45P.” The comet actually passed close enough back in 2011 for Arecibo radar to ping it, one of the very few comets to do so.

Not all apparitions of a given comet are equal, and most passages of Comet 45P were and will be uneventful. Dr. P. Clay Sharrod of the Arkansas Sky Observatory recently wrote a great account of the 1974 passage of Comet 45P, hearkening back to the same year when we were all awaiting Comet Kohoutek and Comet West was yet to come. This account might also hint at what could be in store for comet hunters this weekend.

A sketch of Comet 45P from December 10th, 1974. Image credit and copyright: Dr P. Clay Sherrod.

We managed to nab Comet 45P for the first time this AM from central Florida, though its still a tough catch. Shining at magnitude +7.5, we wouldn’t have otherwise noticed it as we swept along with our trusty Canon 15×45 image-stabilized binocs. Star-hopping finally brought us to the comet, a little fuzzy ‘star’ that stubbornly refused to snap into focus.

Comet 45P from early January, post-perihelion. Image credit and copyright: Sharin Ahmad (@shahgazer).

Unfortunately, the Moon reaches Full on Friday night, entering into the dawn sky this weekend. I’d advise hunting for the comet on every clear morning leading up to this weekend as the comet vaults northward into the pre-dawn sky. Friday night’s subtle penumbral eclipse won’t help much by way of dimming the Moon, though you can always place a house or hill between yourself and the Moon in a bid to block it out and aid in your cometary quest. There’s also a great photo op on February 16, when Comet 45P passes less than three degrees from the globular cluster M3.

As close shaves go, this passage of Comet 45P ranks as the 21^st closest recorded passage of a comet near the Earth. The record goes to Comet Lexell, which passed just 0.0151 AU (1.4 million miles, or just under six times the distance to the Moon) past the Earth on July 1^st, 1770. At its closest, Lexell had a visible coma spanning more than two degrees, more than four times the diameter of a Full Moon. In recent times, the last close passage of a comet other than 45P was Comet IRAS-Araki-Alcock, which zipped 0.063 AU past the Earth on June 12, 1983.

Ah, those were the days… a depiction of the Great Comet of 1769 as seen from Amsterdam, just one year (!) prior to the passage of Lexell’s Comet. Image in the Public Domain.

The gambler’s fallacy would say we’re due for the next big bright comet, though the universe seems to stubbornly refuse to roll the dice. In addition to 45P, 2017 does host a string of binocular comets, including Comet 2P Encke (March), Comet 41P/Tuttle-Giacobini-Kresák (April), Comet C/2015 ER61 PanSTARRS (May), and Comet C/2015 V2 Johnson (June). These are all explored in detail in our free e-book guide to the year, 101 Astronomical Events for 2017 out from Universe Today.

Stay warm on your comet vigil, and let us know of those observational tales of tribulation and triumph.

February 6, 2017February 6, 2017 by David Dickinson

Ancient Annular: Dating Joshua’s Eclipse

Astronomy turns up in fascinating junctures in history. Besides just the romantic angle, we can actually pin down contextual events in ancient history if we can tie them in with a spectacle witnessed in the heavens. A recent look at the story of ‘Joshua’s eclipse’ is one such possible tale.

Lunar and solar eclipses are especially dramatic events, something that would have really made the ancients stop and take notice. A recent study published in an edition of the Beit Mikra Journal (in Hebrew) by researchers from Ben Gurion University may have pinpointed a keypoint in biblical history: the date of the Battle of Gibeon.

This study first came to our attention via the Yahoo! SEML eclipse message board and a recent Times of Israel article. The article makes mention of NASA eclipse data, which is free for anyone to peruse looking over the five millennium canon of solar and lunar eclipses… hey, it’s what we do for fun.

We did obtain a look at a translation of the abstract from the paper, which ends with the following:

“In the period between 1500-1000 BCE which is the relevant time for the biblical story, there were only three eclipses seen from Jerusalem, one total eclipse and two annular eclipses. We show that the most appropriate one is the annular solar eclipse that occurred on October 30 in 1206 BCE at sunset, an appropriate date for the time of conquest and the early settlement period, at the time of Marneptah’ rule in Egypt.”

The path of the eclipse of October 30th, 1206 BC. Credit: NASA/GSFC/Espenak/Meeus.

Joshua 10:12 reads: “Sun, stand still upon Gibeon; and you, Moon, in the valley of Ayalon.”

According to tradition, Joshua commanded the Sun to stand still long enough to defeat the Canaanite kings. Of course, the Sun and the Moon still move during an eclipse be it lunar or solar, though its mostly our planet that’s doing the moving. Still, the actual biblical term “-dom” is open to interpretation, and the researchers chose the Hebrew “to become dark” instead of the King James translation of “to stand still,” or “stationary”.

If this Bible verse sounds familiar, that’s because it turns up in astronomical history again in medieval Europe, when Church proponents used it as supposed proof of geocentricism.

Mid eclipse — Mid-eclipse over central Israel at sunset on October 30th, 1206 BC. Credit: Stellarium.

It’s tough to predict eclipses in distant time. The rotation of the Earth is not entirely smooth, and the minute change in the length of the day (known as Delta T) accumulates to the point that a leap second must be inserted on occasion to keep observed time in sync with reckoned terrestrial time. Braking action by the Sun and Moon, tectonic activity, and even global warming all cause small changes in the Earth’s rotation that slowly build up over time. This means that it’s tough to predict eclipses more than a few thousand years out, where at best we can only judge which continent they might have or will fall on.

“Not everyone likes the idea of using physics to prove things from the Bible,” said researcher Hezi Yitzhak to the Israeli news site Haaretz. “We do not claim that everything written in the Bible is true or took place… but there is also a grain of historical truth that has archaeological evidence behind it.”

The eclipse in question occurred on October 30^th, 1206 BC. This was an annular eclipse, crossing the Atlantic and the Mediterranean and ending over Israel and Jordan at sunset. Researchers pegged this suspect eclipse because of its fit for historical context and visibility. Annularity for the eclipse was 86% obscuration and started at an altitude of nine degrees above the western horizon, and would have still been in progress during its final phases at sunset.

The end of the eclipse path over modern day Israel and Jordan. Credit: NASA/GSFC data.

Lots of eclipses turn up in history. A partial lunar eclipse preceded the fall of Constantinople in 1453, seeming to fulfill prophecy. Solar and lunar eclipses made a showing at lots of battles, including the Second Battle of Syracuse on August 28^th, 412 BC and during the Zulu War on January 22^nd, 1879. A solar eclipse on June 15th, 762 BC mentioned in Assyrian texts pinpoints a crucial time in ancient history, giving us a benchmark for later dates. It’s worth noting that prior to modern times, it seems that battles were the only thing worth writing down…

Still, it’s interesting to imagine the scene as ancient armies clash, only to stop and gaze at the wondrous sight on the horizon: a pair of glowing horns, hanging low in the pre-dusk sky. We caught the 1994 annular eclipse from the Sandusky, Ohio on the shores of Lake Erie and can attest that even a 98% eclipsed Sun is still pretty bright, giving even a clear day a deep steely blue tint. Lower to the horizon though, an annular eclipse is more readily visible to the unaided eye.

You have to be careful when attempting to read ancient texts as astronomical guide books. Great minds, including Kepler and Newton, expended lots of mental juice on attempting to link biblical accounts such as Ezekiel’s Wheel and the Star of Bethlehem with actual astronomical events. We’ll probably never know for sure if a coincidental conjunction graced the sky over the manger in Bethlehem, or if Ezekiel saw the breakup of a brilliant comet, but it’s always fun to imagine and wonder. Then, there’s the inevitable embellishment that accompanies stories that may have been first sparked by meteor showers or sundogs, centuries ago. We don’t, for example, see flaming swords or banners emblazoned with Latin inscriptions across the sky today, though if you can believe medieval accounts, they seemed common back in the day.

And don’t forget: we’ve got our very own history making eclipse (hopefully sans battlefields) this coming August 21^st, 2017 crossing the United States from coast-to-coast.

Though far from conclusive, the results of the study concerning Joshua’s eclipse and the battle of Gideon are interesting to consider. Most likely we’ll never truly know what happened that ancient afternoon, unless, of course, we perfect time travel. What other events remain hidden and lost to time, ready for some historical astro-sleuth to uncover them?

-Can’t get enough of eclipses, historical or otherwise? Check out our original eclipse-fueled sci-fi tales Exeligmos, Peak Season and Class Field Trip.

February 5, 2017February 5, 2017 by Bob King

See a Flirtatious Lunar Eclipse This Friday Night

Penumbral lunar eclipse Oct. 18-19, 2013. Credit: AstroTripper2000

This sequence of photos taken on October 18, 2013 nicely show the different phases of a penumbral lunar eclipse. The coming penumbral eclipse will likely appear even darker because Earth’s shadow will shade to the top (northern) half of the Moon rich in dark lunar “seas” at maximum. Credit: **AstroTripper 2000**

Not many people get excited about a penumbral eclipse, but when it’s a deep one and the only lunar eclipse visible in North America this year, it’s worth a closer look. What’s more, this Friday’s eclipse happens during convenient, early-evening viewing hours. No getting up in the raw hours before dawn.

Lunar eclipses — penumbral, partial and total — always occur at Full Moon, when the Moon, Earth and Sun line up squarely in a row in that order. Only then does the Moon pass through the shadow cast by our planet. Credit: Starry Night with additions by the author

During a partial or total lunar eclipse, the full moon passes first through the Earth’s outer shadow, called the penumbra, before entering the dark, interior shadow or umbra. The penumbra is nowhere near as dark as the inner shadow because varying amounts of direct sunlight filter into it, diluting its duskiness.

To better understand this, picture yourself watching the eclipse from the center of the Moon’s disk (latitude 0°, longitude 0°). As you look past the Earth toward the Sun, you would see the Sun gradually covered or eclipsed by the Earth. Less sunlight would be available to illuminate the Moon, so your friends back on Earth would notice a gradual dimming of the Moon, very subtle at first but becoming more noticeable as the eclipse progressed.

This diagram shows an approximation of the Sun’s position and size as viewed by an observer at the center of the lunar disk during Friday’s penumbral eclipse. More sunlight shines across the Moon early in the eclipse, making the penumbral shadow very pale, but by maximum (right), half the sun is covered and the Moon appears darker and duskier as seen from Earth. During a total lunar eclipse, the sun is hidden completely. Credit: Bob King with Earth image by NASA

As the Moon’s leading edge approached the penumbra-umbra border, the Sun would narrow to a glaring sliver along Earth’s limb for our lucky lunar observer. Back on Earth, we’d notice that the part of the Moon closest to the umbra looked strangely gray and dusky, but the entire lunar disk would still be plainly visible. That’s what we’ll see during Friday’s eclipse. The Moon will slide right up to the umbra and then roll by, never dipping its toes in its dark waters.

During a partial eclipse, the Moon keeps going into the umbra, where the Sun is completely blocked from view save for dash of red light refracted by the Earth’s atmosphere into what would otherwise be an inky black shadow. This eclipse, the Moon only flirts with the umbra.

The moon’s orbit is tilted 5.1 degrees in relation to Earth’s orbit, so most Full Moons, it passes above or below the shadow and no eclipse occurs. Credit: Bob King

Because the moon’s orbit is tilted about 5° from the plane of Earth’s orbit, it rarely lines up for a perfect bullseye total eclipse: Sun – Earth – Moon in a straight line in that order. Instead, the moon typically passes a little above or below (north or south) of the small, circle-shaped shadow cast by our planet, and no eclipse occurs. Or it clips the outer edge of the shadow and we see — you guessed it — a penumbral eclipse.

Earth’s shadow varies in size depending where you are in it. Standing on the ground during twilight, it can grow to cover the entire sky, but at the moon’s distance of 239,000 miles, the combined penumbra and umbra span just 2.5° of sky or about the width of your thumb held at arm’s length.

The moon passes through Earth’s outer shadow, the penumbra, on Feb. 10-11. In the umbra, the sun is blocked from view, but the outer shadow isn’t as dark because varying amounts of sunlight filter in to dilute the darkness. Times are Central Standard. Credit: F. Espenak, NASA’s GFSC with additions by the author

Because the Moon travels right up to the umbra during Friday’s eclipse, it will be well worth watching.The lower left or eastern half of the moon will appear obviously gray and blunted especially around maximum eclipse as it rises in the eastern sky that Friday evening over North and South America. I should mention here that the event is also visible from Europe, Africa, S. America and much of Asia.

This map shows where the eclipse will be visible. Most of the U.S. will see at least part of the event. Credit: F. Espenak, NASA’s GFSC

For the U.S., the eastern half of the country gets the best views. Here are CST and UT times for the different stages. To convert from CST, add an hour for Eastern, subtract one hour for Mountain and two hours for Pacific times. UT stands for Universal Time, which is essentially the same as Greenwich or “London” Time except when Daylight Saving Time is in effect:

This is a simulated view of the Full **Snow Moon** at maximum eclipse Friday evening low in the eastern sky alongside the familiar asterism known as the Sickle of Leo. Created with Stellarium

Eclipse begins: 4:34 p.m. (22:34 p.m. UT)
Maximum eclipse (moon deepest in shadow): 6:44 p.m. (00:43 UT Feb. 11)
Eclipse ends: 8:53 p.m. (2:53 UT Feb. 11)

You can see that the eclipse plays out over more than 4 hours, though I don’t expect most of us will either be able or would want to devote that much time. Instead, give it an hour or so when the Moon is maximally in shadow from 6 to 7:30 p.m. CST; 7-8:30 EST; 5-6:30 p.m. MST and around moonrise Pacific time.

This should be a fine and obvious eclipse because around the time of maximum, the darkest part of the penumbra shades the dark, mare-rich northern hemisphere of the Moon. Dark plus dark equals extra dark! Good luck and clear skies!

February 2, 2017February 3, 2017 by David Dickinson

Superbowl Smackdown: Watch the Moon Occult Aldebaran on Sunday

Daytime Aldebaran — Can you see it? Dave Walker accidentally (!) caught Aldebaran near the daytime Moon on October 19th, 2016. Image credit and copyright: Dave Walker

Author’s note: This Superbowl Sunday event and 101 more like it are featured in our latest free e-book, 101 Astronomical Events for 2017, out now from Universe Today.

Sure, this Superbowl Sunday brings with it the promise of sacks, fumbles and tackles… but have you ever seen the Moon run down a star in the end zone? Just such an event, referred to as an occultation, happens this weekend for folks living around the Mediterranean and — just maybe for some sharp-eyed, telescope-owning observers based around the Caribbean region — this coming weekend.

Update: be sure to watch this Sunday’s occultation of Aldebaran by the Moon courtesy of Gianluca Masi and the Virtual Telescope Project live starting at 22:00 UT/5:00 PM EST:

Live starting at 22:00 UT. Credit: The Virtual Telescope Project

We’re talking about Sunday’s occultation of the bright star Aldebaran by the 64% illuminated waxing gibbous Moon. This is the 2^nd occultation of Aldebaran by the Moon for 2017 and the 28th of the current ongoing cycle of 49 spanning from January 29^th, 2015 to September 3^rd, 2018. The Moon actually occults Aldebaran and Regulus once for every lunation in 2017. We won’t have another year featuring the occultations of two +1^st magnitude stars (Spica and Antares) again until 2024.

Occultation footprint — The footprint for the February 5th occultation of Aldebaran by the Moon. The broken lines show where the occultation occurs during daytime, and the solid lines denote where the occultation occurs under dark skies. Image credit: occult 4.2.

The event occurs under dark skies for observers based around the Mediterranean and under daytime afternoon skies for folks in central America, the Caribbean, northern South America and the Florida peninsula, including Astroguyz HQ based in Spring Hill, just north of the Tampa Bay area. We’ve managed to spy Aldebaran near the daytime Moon while the Sun was still above the horizon using binocs, and can attest that the +1st magnitude star is indeed visible, if you know exactly where to look for it.

Note that, like solar eclipses belonging to the same saros cycle, occultations of Aldebaran in the ongoing cycle drift north and westward from one to the next, to the tune of about 120 degrees longitude. Though most of North America sits this one out, we do get a front row seat for next lunation’s occultation of Aldebaran on the evening of March 4/5th. The next one is the best bright star occultation of Aldebaran by the Moon for North America in 2017. And be sure to check out the Moon this Sunday evening after the big game, and note Aldebaran hanging just off of its bright limb.

Moon motion — No, the wind is not shaking the ‘scope… Sharin Ahmad chronicled the motion of the Moon past Aldebaran from Kuala Lumpur, Malaysia last month. Image credit and copyright: Shahrin Ahmad (@shahgazer)

The ref will have a close call to make for this one. The northern grazeline in Florida might make this an especially interesting event to watch, though it’ll be challenge, as the occultation occurs in the afternoon under daylight skies. This crosses right along near the cities of Jacksonville and Gainsville. Clear, deep blue high contrast skies are key, and we’ll be watching from Astroguyz HQ north of Tampa Bay during this event.

The northern grazeline across the Florida peninsula for Sunday’s ‘big game’. Credit: Dave Dickinson.

Here are some key times from the occultation zone (noted in Universal Time):

Tampa, Florida

Ingress: 20:08 UT/Moon altitude: 23 degrees

Egress: 20:34 UT/Moon altitude: 29 degrees

Bogota, Columbia

Ingress: 19:34 UT/ Moon Altitude: 49 degrees

Egress: 20:29 UT/ Moon altitude: 31 degrees

The view from Jimena de la Frontera Spain just before the occultation. Credit: Stellarium.

Rome, Italy

Ingress: 20:21 UT/Moon altitude: 37 degrees

Egress: 23:12 UT/ Moon altitude: 28 degrees

Tel Aviv, Israel

Ingress: 22:39 UT/Moon altitude: 16 degrees

Egress: 23:29 UT/Moon altitude: 5 degrees

Casablanca, Morocco

Ingress: 21:49 UT/ Moon altitude: 61 degrees

Egress: 23:07 UT/ Moon altitude: 45 degrees

Note that this occultation spans five continents, a truly worldwide event. The International Occultation Timing Association (IOTA) maintains a page with an extensive list of times for cities worldwide. Note that when the Moon tackles Aldebaran, its also crossing the scrimmage line of the Hyades open cluster, so expect numerous occultations of fainter stars worldwide as well.

Aldebaran is the brightest star along the Moon’s path in our current epoch, along with runner-ups Spica, Regulus and Antares. Though Aldebaran is 1.5 times the mass of our Sun, it’s also 65 light years away, and only appears 20 milliarcseconds (mas) in size, about the equivalent of a 40 meter diameter crater from the distance of the Moon. Still, you might just notice a brief pause as Aldebaran fades then winks out on the dark limb of the Moon, a tiny hitch betraying its diminutive angular size.

And the clockwork gears of that biggest game of all, the Universe, grind on. Don’t miss this first big ticket astronomical event for February 2017, coming to a sky above you. Next up, we’ll watching out for another bright star occultation, two eclipses, and the close passage of a comet near the Earth.

Stay tuned!

January 21, 2017January 24, 2017 by Bob King

How to See the Space Station Fly in Front of the Moon

A beautiful ISS transit on June 19 2015 recorded at Biscarrosse, France. Credit: David Duarte

What strange creature is this flitting across the Moon? Several members of the European Space Agency’s Astronomy Center captured these views of the International Space Station near Madrid, Spain on January 14 as it flew or transited in front of the full moon. Credit: Michel Breitfellner, Manuel Castillo, Abel de Burgos and Miguel Perez Ayucar / ESA

One-one thou… That’s how long it takes for the International Space Station, traveling at over 17,000 mph (27,300 kph), to cross the face of the Full Moon. Only about a half second! To see it with your own eyes, you need to know exactly when and where to look. Full Moon is best, since it’s the biggest the moon can appear, but anything from a half-moon up and up will do.

The photo above was made by superimposing 13 separate images of the ISS passing in front of the Moon into one. Once the team knew when the pass would happen, they used a digital camera to fire a burst of exposures, capturing multiple moments of the silhouetted spacecraft.

The ISS transits the Full Moon in May 2016

The ISS is the largest structure in orbit, spanning the size of a football field, but at 250 miles (400 km) altitude, it only appears as big as a modest lunar crater. While taking a photo sequence demands careful planning, seeing a pass is bit easier. As you’d suspect, the chances of the space station lining up exactly with a small target like the Moon from any particular location is small. But the ISS Transit Finder makes the job simple.

This is a screen grab from the homepage of Bartosz Wojczy?ski’s most useful ISS Transit Finder. Credit: Bartosz Wojczy?ski

Click on the link and fill in your local latitude, longitude and altitude or select from the Google maps link shown. You can always find your precise latitude and longitude at NASA’s Latitude/Longitude Finder and altitude at Google Maps Find Altitude. Next, set the time span of your Moon transit search (up to one month from the current date) and then how far you’re willing to drive to see the ISS fly in front of the Moon.

When you click Calculate, you’ll get a list of events with little diagrams showing where the ISS will pass in relation to the Moon and sun (yes, the calculator also does solar disk crossings!) from your location. Notice that most of the passes will be near misses. However, if you click on the Show on Map link, you’ll get a ground track of exactly where you will need to travel to see it squarely cross Moon or Sun. Times shown are your local time, not Universal or UT.

A beautiful ISS transit on June 19 2015 recorded at Biscarrosse, France. The photographer used CalSky, another excellent satellite site, to prepare a week in advance of the event. This composite image was made with a Canon EOS 60D. Notice how bright the space station appears against the moon due to the lower-angled lighting across the lunar landscape at crescent phase compared to full, when the ISS appears in silhouette. Credit: David Duarte

The map also includes Recalculate for this location link. Clicking that will show you a sketch of the ISS’ predicted path across the Moon from the centerline location along with other details. I checked my city, and while there are no lunar transits for the next month, there’s a very nice solar one visible just a few miles from my home on Feb. 8. Remember to use a safe solar filter if you plan on viewing one of these!

The ISS transits the Sun on May 3, 2016. Click for details on how the photo was taken. Credit: Szabolcs Nagy

While you might attempt to see a transit of the ISS in binoculars, your best bet is with a telescope. Nothing fancy required, just about any size will do so long as it magnifies at least 30x to 40x. Timing is crucial. Like an occultation, when the moon hides a background star in an instant, you want to be on time and 100% present.

Make sure you’re set up and focused on the moon or sun (with filter) at least 5 minutes beforehand. Keep your cellphone handy. I’ve found the time displayed at least on my phone to be accurate. One minute before the anticipated transit, glue your eye to the eyepiece, relax and wait for the flyby. Expect something like a bird in silhouette to make a swift dash across the moon’s face. The video above will help you anticipate what to expect.

The next lunar transit nearest my home is an hour and a half away in the small town of Biwabik, Minn. according to the ISS Transit Finder. On Jan. 30 at 8:00:08 p.m local time, the ISS will cross the crescent moon from there. Once you know the time of the prediction and the exact latitude and longitude of the location (all information shown in the info box on the map using the ISS Transit Finder), you can turn on the satellites feature in the free Stellarium program (stellarium.org), select the ISS and create a simulated, detailed path. Created with Stellarium

Even if you never go to the trouble of identifying a “direct hit”, you can still use the transit finder to compile a list of cool lunar close approaches that would make for great photos with just a camera and tripod.

The Transit Finder isn’t the only way to predict ISS flybys. Some observers also use the excellent satellite site, CalSky. Once you tell it your location, select the Lunar/Solar Disk Crossings and Occultations link for lots of information including times, diagrams of crossings, ground tracks and more.

I use Stellarium (above) to make nifty simulated paths and show me where the Moon will be in the sky at the time of the transit. When you’ve downloaded the free program, get the latest satellite orbital elements this way:

* Move you cursor to the lower left of the window and select the Configuration box
* Click the Plugins tab and scroll down to Satellites and click Configure and then Update
* Hover the cursor at the bottom of the screen for a visual menu. Slide over to the satellite icon and click it once for Satellite hints. The ISS will now be active.
* Set the clock and location (lower left again) for the precise time and location, then do a search for the Moon, and you’ll see the ISS path.

There you have it — lots of options. Or you can simply use the Transit Finder and call it a day! I hope you’ll soon be in the right place at the right time to see the space station pass in front of the Moon. Checking my usual haunts, I see that the space station will be returning next weekend (Jan. 27) to begin an approximately 3-week run of easily viewable evening passes.