May 2019 • Astronomy.com

Astronomy Insights A Digital Supplement to Astronomy Magazine

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Prime Time for Jupiter

Longtime photographer Christopher Go takes you step by step through the process of imaging this gas giant.

ASTROIMAGING

JUPITERHow to image

esides Earth, Jupiter is the easiest planet to capture photographically. Its high surface brightness and large angular diameter make detailed imaging accessible to any telescope size. Even a small scope can resolve major features, like the Great Red Spot.

And now’s a great time to start shooting the gas giant because it lies high in the sky. Professional astronomers at the Jet Propulsion Laboratory are requesting amateur images to sup-port the Juno spacecraft, which will arrive at Jupiter in July.

As someone who has been imaging Jupiter for a decade, I’ve seen and tried a lot of equipment and many processing techniques. Because I have “been there, done that,” the tips and techniques I’ve developed can help you get started the right way. Take it slow, be sure you understand an idea before you move to the next one, join an online imaging forum, ask lots of questions, and then head out and shoot!

B

The author took this image of Jupiter on March 5, 2015, at 12h54m UT. It shows the main equatorial belts, the Great Red Spot, and a whole lot more detail. ALL IMAGES:

CHRISTOPHER GO

2 ASTRONOMY INSIGHTS • MAY 2019

Lucky imagingCurrently, the method I and most other amateurs use to capture planets is called “lucky imaging.” This uses a small video camera attached to a telescope. You later process the video with software that lets you stack frames. The program has a routine to perform a check on each frame. It then arranges them in order of quality, letting you stack the best ones to pro-duce a final image.

Which camera?One of the most common ques-tions people ask is whether to get a monochrome or color camera. Color cameras are easy to use and less expensive overall because you don’t need additional accessories like fil-ters and filter wheels.

For beginners I always rec-ommend a color camera. And I have one other tip: When your target planet lies below an alti-tude of 70°, use an atmos-pheric dispersion corrector to offset the effects thicker layers of air have on images.

For the highest-quality images, amateur astronomers should use monochrome cam-eras because their pixels lie closer together than those in color cameras. Monochrome models also are more sensitive.

I use a Celestron Skyris 236M (pictured at lower right) for my monochrome imaging and the Celestron NexImage 5 for my color images.

Telescope and mountAlmost any telescope can pro-duce decent images of Jupiter. That said, use the largest aper-ture you can. Long-focal-length telescopes are ideal for imag-ing Jupiter because they offer higher magnifications.

An optical tube is only as good as its mount, however. As much as it is up to you, choose a sturdy polar-aligned mount.

This necessity (I think it’s more than an accessory) will make your imaging easier.

Other accessoriesIf you select a monochrome camera, you’ll need a filter wheel with a red, green, and blue (RGB) filter set to produce color images. Beyond standard color shots, I often use a meth-ane-band filter, an ultraviolet filter, and an infrared filter. Each of these reveals different layers in Jupiter’s atmosphere. Note that the images you’ll get through these filters will not be as pleasing to the eye as your color shots.

I also suggest a motorized focuser. This accessory will allow fine focus, which is nec-essary to get the best image.

You also may want to use a Barlow lens to increase image size, but I can’t tell you which one exactly. Its magnification depends on the focal ratio of the scope, the pixel size of the camera, and your typical seeing conditions (how steady the air above your imaging site is). A variable Barlow, like the Astro-Physics Advanced Convertible Barlow, allows flexibility.

Imaging preparationThe most important step before you start to image is to make sure that the telescope is at ambient temperature. A telescope warmer than its surroundings will cause tube currents that negatively affect image quality. Also, avoid imaging close to asphalt that’s been in the Sun all day, a hot roof, or other such structures.

JUPITERFOR THE

HIGHEST-QUALITY IMAGES, AMATEUR

ASTRONOMERS SHOULD USE

MONOCHROME CAMERAS

BECAUSE THEIR PIXELS LIE CLOSER TOGETHER THAN

THOSE IN A COLOR CAMERA.

This image of the giant planet, which

the author captured April 9, 2015, at 10h59m UT, shows great detail and accurate color. The Great Red Spot at the left edge is just starting to rotate into view.

If you use a mono-chrome camera to

shoot Jupiter, you have to capture exposures through red, green, and blue filters to produce a color image.

Christopher Go has produced images of Jupiter nearly every clear night for a decade from Cebu, Philippines. Contact him at chris@cstoneind.com.

W W W.ASTRONOMY.COM 3

The most important factor in getting the best image is see-ing. This means the site you choose for capturing data is critical. If possible, try to image for three or four days straight from several locations, then pick the one with the highest-quality air. Selecting a site

FireCapture’s con-trol screen offers

numerous options for processing planetary images.

Many planetary imagers cut their

teeth on Registax, which came onto the amateur astronomy scene in May 2002.

If you use the “Wavelet” area in

Registax carefully, your images will dramatically improve.

based on seeing is far more important than selecting a dark site. After all, Jupiter usually ranks as the fourth-brightest object in the sky.

Image captureFireCapture is currently the standard image-capture soft-

ware. It supports different camera manufacturers and controls ASCOM (short for AStronomy Common Object Model) compliant mounts, filter wheels, and focus-ers. Also important to some people: This software is free. Here are some tips on using FireCapture:

1. In “Capture Settings,” make sure that the file name includes the object’s name, the date, and the Universal Time. Also, synchronize your com-puter’s clock with an atomic clock. When doing mono-chrome imaging, make sure you indicate the filter used.

2. Use “Region of Interest” (ROI) to reduce the capture frame size. Using ROI creates smaller files, increases the maximum frame rate, and

makes processing faster. You can do ROI by hold-pressing your mouse’s left button and outlining the area around Jupiter. Make sure you leave some space for inaccuracies in your mount’s drive.

Gain and exposure time controls

Exposure time limit

Histogram should be 80-90% by adjusting gain and exposure time.

4 ASTRONOMY INSIGHTS

3. Set a time limit for cap-turing Jupiter. This is the “Limit” button on the control panel of FireCapture. Because of the planet’s fast rotation, there are constraints on how long an exposure can be for each frame. For apertures smaller than 8 inches, the length is around 60 seconds; 40 seconds for an 11-inch; and 30 seconds for a 14-inch scope.

4. Two controls affect the brightness of Jupiter. These are “Gain” and “Exposure Time.” A higher gain brightens Jupiter but will produce a grainy image. Faster exposure times would allow faster frame rates, but they will dim the object.

Use the image’s histogram as a guide for these two set-tings. When imaging Jupiter, the histogram should peak at around 80 to 90 percent.

One other thing to remem-ber is that the frame rate func-tions as the inverse of the exposure time. I recommend exposure times for Jupiter between 1/50- and 1/80-second, then setting the gain to achieve the recommended histogram. But this is not a hard rule. Exposure times will depend on your seeing.

5. When imaging using the narrowband methane or ultra-violet filters, bin your images at 2x2. This technique allows the camera to use four pixels (in a 2x2 matrix) as though they were a single pixel. Exposure times for these filters vary from 0.25 second to 2 seconds.

StackingStacking software sorts video frames by quality. You then choose how many frames to stack for your final image. I recommend AutoStakkert!2 (AS!2). One nice feature is its ability to do batch processing by opening multiple files for stacking. Beginners find AS!2 easy to use. Here are the steps:

1. Open the file.2. Press the “Place AP on

Grid” button. I recommend alignment point (AP) sizes of

50 or 100 depending on the size of the image.

3. In the “Stack Options” section, use percentage for the amount of image you want to stack. When the seeing is good use 70 to 80 percent. For bad seeing, use 50 to 60 percent.

I normally use 1.5x drizzle for most of my images to increase their size. Test different drizzle settings, and find out which works best for your con-ditions and setup. AS!2 will save the resulting stacked images in a folder automatically.

Wavelet sharpeningRegistax was early stacking software that started the ama-teur planetary imaging revolu-tion. Its most powerful tool is the wavelet-sharpening func-tion, which I highly recom-mend. Here are some tips for using wavelet:

1. The “Layer” sliders con-trol sharpening. Slider 1 is for fine sharpening, and it gets coarser as the slider number increases. I normally use only sliders 1, 2, and 3 and leave sliders 4 through 6 set at 1.0.

Larger images require higher slider values. Don’t push too much or you will introduce more grain in the image.

2. Increasing the value of the “Initial Layer” and the “Step Increment” will help sharpen your image. Test dif-ferent settings to see which works best with your setup. Then save them when you find the sweet spot.

Color combineColor camera users can skip this step. Image processing

To derotate an image of the giant planet,

first open the “Image Measurement” window in WinJupos.

The second step is to open the “De-rotation

of images” window.

Align wire frame to image using F11.

Enter Universal Time as accurately as possible.

Load Image Measurement files

Reduce LD value to reduce edge artifacts

Start derotation

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software like Photoshop and Gimp can be used to align colors. Note: Apply wavelets before you color combine. Here’s how to combine colors in Photoshop:

1. Open the wavelet-pro-cessed files.

2. Convert the images into gray scale (“Image,” then “Mode,” then “Grayscale”)

3. Next, at the “Channels” windows, use the “Merge Channels” function, and use the “RGB Color” option. Make sure each file corresponds to the correct color channel.

4. Use the “Move” tool to do alignment adjustment. I suggest you align the Red and Blue channels to the Green channel. Save your color image using the Green filter time.

DerotationThe fast rotation of Jupiter limits the exposure time. Fortunately, WinJupos software has added a feature called “De-rotation,” which allows exposure times beyond what was possible with a single image. Now, you can capture and derotate multiple image sets into an image, which will produce less noise than a single image.

For color, you capture mul-tiple consecutive images. But for monochrome, you must

capture three sets (R, G, and B) of sequences. Do not do con-secutive captures with the same filter, or the resulting image will have red and blue edges. You have to do an RGB set.

When seeing is good, three or four image sets are suffi-cient, but when atmospheric conditions are bad, capture more image sets. De-rotation is a two-stage process.

STAGE 1:1. Under “Recording,”

open the “Image Measurement” window.

2. Load the image. Enter the median observation time. For color images, this is the time on the file name plus half of your exposure time. For mono-chrome images, this should be the green start time plus half the time you exposed on one channel. Make sure you enter the time accurately.

3. Press F11 to automatically align the wire frame to the image. If there seems to be some offset on the auto-align, use the arrow keys to adjust the X and Y positions, the “N” and “P” keys to adjust rotation, and “Page Up” and “Page Down” to adjust the size of the wire frame. Save the image measure-ment. Repeat these procedures for the image set.

STAGE 2:1. Open the “De-rotation of

Images” window under “Tools.”2. Load the Image Meas-

urement (*.ims) files that you made in Stage 1.

3. Choose the output file type and orientation preference.

4. Compile the image. Your

result will carry the midtime of the component images.

Final processingUsing image-processing soft-ware, apply slight unsharp masking to improve the image. Some useful tools in Photoshop are the “Despeckle” and the “Dust and Scratches” filters, which remove noise and grain. You’ll find them in the “Filters,” then “Noise” menus.

Impact detectionSince June 2010, amateur imag-ers have detected four impact events. In response, program-mers developed Jupiter Impact Detection (JID) software to search for them automatically.

So be sure to run all of your captured video streams through JID. Who knows? You might get lucky and achieve your 15 minutes of fame.

Support researchFinally, you can help the cause of science by uploading your images to the Jupiter section of the Association of Lunar and Planetary Observers, the International Outer Planets Watch website, and the JPL Juno support website. This will allow professionals to use your images to give us all a better understanding of Jupiter.

When submitting images, include the date and time of capture, name of imager and location, and the three central meridian system timings of Jupiter. You’ll find them in WinJupos under “Tools,” then “Ephemerides.”

WHEN SEEING IS GOOD, THREE

OR FOUR IMAGE SETS

ARE SUFFICIENT, BUT WHEN

CONDITIONS ARE BAD,

CAPTURE MORE IMAGE SETS.

On June 3, 2010, the author imaged

an impact scar (arrow) in Jupiter’s atmosphere discovered by Australian amateur astronomer Anthony Wesley.

MEET THE AUTHORImaging wizardChristopher Go has sent an astounding 977 sets of images of Jupiter to Astronomy maga-zine, starting in early 2007, and he carefully processes each shot before sending it. This amount of work alone places him in the top tier of planetary imagers. Recently, he began teaching others how to image Jupiter. Christopher Go

COU

RTES

Y CE

LEST

RON

6 ASTRONOMY INSIGHTS • MAY 2019

Antares

Jupiter

SAGIT TARIUS

SC ORPIUSLUPUS

LIBR A

OPHIUCHUS

June 10, 11 P.M.Looking south-southeast

Saturn 10°

Jupiter at its finest

Visible to the naked eye

Visible with binoculars

Visible with a telescope

MARTIN RATCLIFFE and ALISTER LING describe the solar system’s changing landscape as it appears in Earth’s sky.

June 2019: Jupiter dazzles all night

SKYTHISMONTH

lthough June nights may be short, you can pack a lot of planet view-ing into those limited hours. Most observ-

ers will spend the bulk of their time with Jupiter, which reaches peak visibility and is up all night. But you’ll also want to watch Mercury and Mars as they have their closest evening conjunction in more than a decade. Be sure to turn your attention toward Saturn and its magnificent rings as midnight approaches, then wrap up a memorable night with a view of Venus in morn-ing twilight.

But your first order of business these June nights should be to track down Mercury and Mars. On the 1st, Mercury shines at magni-tude –1.0 and appears 6° high

A

more prominent. This is earth-shine — sunlight that bounces off Earth, hits the Moon, and reflects back to our eyes. The following evening, a slightly fatter crescent Moon appears 6° to Mars’ upper left.

Over the next two weeks, Mercury climbs higher and Mars drops lower. The solar system’s smallest planets are destined for a dramatic meet-ing just after midmonth. On June 17, the two appear side by side with 28' — just less than the Full Moon’s diameter — between them. (This is the separation observers in central North America will see; the planets appear slightly farther apart from the eastern part of the continent and a bit closer from farther west.)

On the evening of the 18th, the two stand just 18' apart — the closest they have been to each other in the evening sky in 13 years. Mercury now lies above Mars and shines at mag-nitude 0.1, some five times brighter than its companion. This close conjunction is

in the west-northwest a half-hour after sunset. It stands out quite nicely in the twilight glow. Four other objects join the inner planet. Capella, at magnitude 0.1 the brightest star in Auriga, stands 21° to Mercury’s upper right. Mars lies 16° to Mercury’s upper left and at the same altitude as Capella. Glowing at magni-tude 1.8, the Red Planet may be hard to see in twilight without binoculars. Finally, the twin stars Castor and Pollux in Gemini appear 13° directly above the slightly fainter Mars.

A two-day-old crescent Moon joins the party June 4. Luna lies 6° to Mercury’s left, and both stand some 9° high 30 minutes after sundown. As the sky darkens, watch the unlit side of the Moon grow

merely a line-of-sight effect. Mars currently lies on the far side of the Sun from Earth while Mercury is on the near side. The view through a tele-scope confirms this: Even though Mars is physically 40 percent larger than Mercury, it appears only 3.7" across — half as big as the inner planet’s 7.4" diameter. A telescope also shows the con-trast between ruddy Mars’ nearly full disk and whiter Mercury’s half-lit phase.

Following this close con-junction, Mercury continues to edge away from the Sun. It reaches greatest elongation June 23, when it lies 25° east of our star and appears 11° high a half-hour after sunset. It then starts to sink closer to the horizon, ending the month 3.8° to Mars’ left.

As Mercury and Mars set in the northwest, Jupiter rises in the southeast. The solar system’s largest planet comes to opposition June 10, when it lies opposite the Sun in our sky and remains visible

Small telescopes reveal details in Jupiter’s cloud bands when the gas giant looms large, as it does throughout June. In this Hubble Space Telescope image, the Great Red Spot looks like a bloodshot eye with the shadow of Ganymede representing its pupil. NASA/ESA/A. SIMON (GSFC)

The giant planet peaks at opposition June 10, but it reigns supreme against the backdrop of Ophiuchus all month. ALL ILLUSTRATIONS: ASTRONOMY: RICK JOHNSON

8 ASTRONOMY INSIGHTS • MAY 2019

Pearly noctilucent clouds

METEORWATCH

Despite the lack of major meteor showers in June, sporadic meteors continue to light up the sky. These random flashes arise when tiny grains of dust slam into Earth’s atmosphere and friction with air molecules incinerates them. Under a dark sky, observers typically see a half-dozen or so of these random meteors per hour.

Similarly fine meteoritic dust plays a role in producing summer’s gorgeous noctilucent clouds. These silver-blue clouds form about 50 miles up (10 times higher than cirrus), where Earth’s atmo-sphere is coldest, when ice crystals

Early summer’s twilight clouds

all night. Opposition brings Jupiter closest to Earth, so it shines at its brightest for the year: magnitude –2.6. It brings a touch of brilliance to the otherwise faint constellation Ophiuchus the Serpent-bearer.

Jupiter’s proximity also makes it appear larger than at any other time in 2019. Its 46"-diameter disk should dis-play a wealth of detail through telescopes of all sizes. A paral-lel pair of relatively dark belts, one on either side of a brighter zone that coincides with the planet’s equator, dominates the view. In moments of steady seeing, look for a whole series of alternating belts and zones as well as the dusky north and south polar regions. You also might notice several dark and white spots lurking near the boundaries between the belts and zones. The Great

Ptolemaeus, Alphonsus, and Arzachel

RISINGMOON

Three magnificent large craters beckon observers the evening of June 10, when the Moon is less than a day past First Quarter phase and appears slightly more than half-lit. The northernmost and largest of the three craters, Ptolemaeus, lies just south of the lunar equator. It sports a rugged rim that casts long shad-ows onto the relatively smooth floor. A small crater northeast of Ptolemaeus’ center affords a good test of your telescope’s optics and seeing conditions.

Like most large impact fea-tures, Ptolemaeus probably pos-sesses a complex central peak — but you won’t see it no mat-ter how hard you look. Lunar sci-entists suspect that it lies buried under deposits sprayed out dur-ing the excavation of giant Mare Imbrium to the northwest. You might also glimpse a few subtle depressions, telltale signs of

ancient craters hidden under a blanket of debris.

The smaller impact that cre-ated Alphonsus immediately to the south of Ptolemaeus pro-duces more distinct features and a higher central peak. Return to this feature every hour or so and note how quickly the spire’s shadow retreats under the rising Sun. The unusual ridge that bisects Alphonsus lines up with other linear features that point back toward Imbrium.

The youngest of the three craters is Arzachel to the south. Its rim and inner walls appear sharper than those of its north-ern neighbors, which suffered many more millennia of impacts.

Don’t hesitate to return to this region on subsequent nights. Although the higher Sun masks topographic relief, it reveals surface composition. Notice the handful of darker

A terrific trio of conspicuous craters

The First Quarter Moon boasts three large and spectacular craters just south of the lunar equator. CONSOLIDATED LUNAR ATLAS/UA/LPL; INSET: NASA/GSFC/ASU

gray spots on Alphonsus’ floor. These are deposits of ash gently sprayed out during vol-canic eruptions. Spectroscopic

studies show the composition of the ash is similar to that of the lava that welled up to flood the large lunar maria.

N

E

Ptolemaeus

condense on dust particles. They typically appear in early summer from latitudes between 50° and 60° north.

Search for them in twilight an hour or two after sunset, when our star still illuminates these high-altitude clouds.

Alphonsus

Arzachel

June’s extended twilight offers ideal conditions for northern skygazers to see these highly reflective, high-altitude clouds. NASA

Jupiter reaches its 2019 peak June 10, when the gas giant planet shines at magnitude –2.6 and spans 46" through a telescope.

OBSERVING HIGHLIGHT

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E

N

Path of Comet ASASSN

30

27

24

21

18

June 15

ν

ξ2

CETUS

0.5°

Comet ASASSN (C/2018 N2)

W

S

GanymedeEuropa

Io

Callisto Jupiter

June 11, 4:00 A.M. EDT 1'

Hunt down Jupiter’s four bright satellites

COMETSEARCH

Comet observers often hope a new discovery will herald a bright target to feed their pas-sion. This does happen, though not often. Two arrivals bright-ened to 9th magnitude in late 2018, but unless we get a similar surprise this month, we’ll have to be satisfied with a comet that reaches only 12th magnitude.

To catch Comet ASASSN (C/2018 N2), wait for the Moon-free period at the end of June. ASASSN — short for the All- Sky Automated Survey for Supernovae program — then resides in northeastern Cetus the Whale and rises about an

hour before morning twilight commences. Look for the faint smudge of light as it glides northward between magnitude 4.9 Nu (ν) Ceti and magnitude 4.3 Xi2 (ξ2) Cet. Astronomers dis-covered this comet in July 2018, and it appears destined to peak at 11th magnitude this autumn.

A harder target lies on the border of Centaurus and Lupus in early June. Comet ATLAS (C/2017 M4) passes between magnitude 2.7 Beta (β) Lupi and magnitude 3.1 Kappa (κ) Centauri during June’s first week. You’ll need a 12-inch or larger scope to spot this 13th-magnitude object.

A killer takes aim at the Whale

EVENING SKY MIDNIGHT MORNING SKY Mercury (northwest) Jupiter (south) Venus (northeast) Mars (northwest) Saturn (southeast) Jupiter (southwest) Jupiter (southeast) Saturn (southwest) Uranus (east) Neptune (southeast)

WHEN TO VIEW THE PLANETS

Red Spot appears about half the time — whenever the plan-et’s 10-hour rotation carries it onto Jupiter’s Earth-facing hemisphere.

The sharpest views of the giant world come when it lies highest in the south. Jupiter peaks at an altitude of about 30° at 1 a.m. local daylight time the night of opposition. It reaches the same benchmark about a half-hour earlier with each passing week. Still, the planet lies nearly as high and the views are almost as good for a couple of hours on either side of these times.

Jupiter’s four brightest moons create a scene that changes dramatically from night to night. Their motions sometimes appear noticeable even within minutes, particu-larly when a satellite transits

minutes, you should notice its shadow immediately to the moon’s east, with the two over-lapping. Ganymede lies north of Io and begins to transit at 11:28 p.m. Its shadow falls on the cloud tops just southeast of the moon. Because Ganymede lies farther from Jupiter than Io, its shadow appears slightly more separated from the moon. Io completes its transit at 12:33 a.m., when Ganymede is about halfway across the giant planet’s disk. The outer moon completes its trek around 1:40 a.m.

Saturn lies 30° east of Jupiter, which means it trails about two hours behind its bigger brother. The ringed planet rises around 11 p.m. local daylight time June 1 and some two hours earlier by month’s end.

the planet’s face or lies near the limb.

The night of opposition offers a good opportunity to acquaint yourself with these so-called Galilean moons. If you look during the morning hours of June 11, you’ll see Io, Europa, and Ganymede lined up to Jupiter’s east while Callisto stands alone to the planet’s west.

The month’s most dra-matic scene occurs the follow-ing night, however. Both Io and Ganymede start to cross Jupiter’s disk the evening of June 11. But with the gas giant so close to opposition, the shadow that each satellite casts falls onto the jovian cloud tops almost directly beneath the moon.

Io’s transit begins at 10:22 p.m. EDT. Within five

Saturn lies in northern Sagittarius, just south of that constellation’s Teaspoon asterism. It shines at magni-tude 0.2 in mid-June and appears four times brighter than any of the Archer’s stars.

The best time to view Saturn through a telescope occurs during the early morn-ing hours when it climbs highest in the south. Even the smallest telescope delivers stunning views. The planet’s disk measures 18" across while the rings span 41" and tilt 24° to our line of sight. Saturn’s disk shows little detail, though you might spot an equatorial belt and a dark polar hood.

Although Saturn’s moons don’t glow as brightly as Jupiter’s Galilean satellites, small scopes reveal at least

Reserve some time on June mornings to track down this faint comet as it slides to the northeast against the background stars of Cetus.

The giant world’s moons show up nicely through small scopes, but they can be tricky to identify. Their arrangement at opposition makes the task easy.

10 ASTRONOMY INSIGHTS • MAY 2019

Mars Mercury

PolluxCastor

GEMINI

June 17, 45 minutes after sunsetLooking west-northwest

5°

E

N

Path of Pallas

July 1

26

21

16

116

June 1

6

2

C OMA BERENICES

BO ÖTES

1°

Pallas continues its nice run

Mercury tangos with Mars

GET DAILY UPDATES ON YOUR NIGHT SKY AT www.Astronomy.com/skythisweek.

Asteroid 2 Pallas glows at 9th magnitude in June, making it a nice target for asteroid seekers. Visible with some effort through binoculars, it’s a cinch to find with the extra light-gathering power of a small telescope.

Pallas lies high in the south after darkness falls. To find it, first locate Arcturus, the magni-tude –0.04 orange giant in Boötes that ranks as the night sky’s fourth-brightest star. Next, move 6.4° west-northwest to 5th-magnitude 6 Boötis, then another 2.4° northwest to 6th-magnitude 2 Boo. From there, cross the border into eastern Coma Berenices, Berenice’s Hair,

and star-hop to Pallas’ position with the help of the chart below.

If you want to see the aster-oid move in a single evening, June 12 and 26 offer the best chances. Both nights, Pallas skims near a similarly bright star that helps you gauge its motion.

When Heinrich Olbers dis-covered Pallas in 1802, astrono-mers thought it might be the second “missing planet” in what seemed like an abnormally large gap between Mars and Jupiter. Scientists later figured out that the gravity of massive Jupiter prevented any major planet from forming at that distance from the Sun.

LOCATINGASTEROIDSTangled up in Berenice’s tresses

four of them. Titan is the easi-est. It shines at 8th magnitude and shows up through any instrument. This large moon orbits Saturn in 16 days, pass-ing south of the ringed world the mornings of June 5 and 21 and north of the planet on the 13th and 29th. Look for three 10th-magnitude moons — Tethys, Dione, and Rhea — closer to Saturn.

Scan 60° east-northeast of Saturn and you’ll arrive at Neptune. The solar system’s most distant major planet rises shortly after 1 a.m. local day-light time June 15 and climbs 25° above the southeastern horizon by the time twilight begins. Neptune glows at mag-nitude 7.9, so you’ll need bin-oculars or a telescope to see it.

The outer world resides in northeastern Aquarius, in the same binocular field as magni-tude 4.2 Phi (ϕ) Aquarii. It begins June 1.2° east-northeast of this star and crawls 0.1° far-ther away by the latter half of the month. This places the planet within 0.4° — slightly less than the Full Moon’s diameter — south of the mag-nitude 5.6 star 96 Aqr. When viewed through a telescope, Neptune displays a blue-gray disk that appears 2.3" across.

Uranus slowly emerges into a dark sky by the end of June. On the 30th, it rises around 2 a.m. local daylight time and climbs 15° high in the east by

the time twilight starts to paint the sky. The planet shines at magnitude 5.8 and shows up quite easily through binoculars.

The hardest part of finding Uranus is zeroing in on the right star field. The world lies in southern Aries, about 10° south of the Ram’s brightest star, magnitude 2.0 Hamal (Alpha [α] Arietis). This is a sparse area of sky, however. First locate 6th-magnitude 19 Ari, which lies 8° south of Hamal and shows up to the naked eye from under a dark sky. Center 19 Ari in your binoculars and you’ll see Uranus 2.4° to its south. To confirm your planet sight-ing, swing a telescope in its direction. Uranus shows a 3.5"-diameter disk with a dis-tinctive blue-green color.

Morning twilight is well underway before our final planet appears. Venus rises an hour before the Sun on June 1 in the company of a slender crescent Moon. The two stand about 6° apart and a similar distance above the eastern horizon a half-hour before sunrise. Although Venus shines brilliantly at magnitude –3.8, the Sun’s glare drowns it out within the next 15 minutes.

Venus slowly sinks lower as the month progresses. It

stands just 3° high a half-hour before sunup June 30, when you’ll need a haze-free sky and an unobstructed horizon to see it against the twilight glow. The inner planet is heading toward its mid-August supe-rior conjunction, and will dis-appear from view in early July.

Earth reaches its summer solstice at 11:54 a.m. EDT on June 21. This marks the instant

when the Sun lies farthest north in our sky, and is the reason why the days are so long and the nights so short in the Northern Hemisphere.

Martin Ratcliffe provides plane-tarium development for Sky-Skan, Inc., from his home in Wichita, Kansas. Alister Ling, who lives in Edmonton, Alberta, has watched the skies since 1975.

These two planets slide within 0.3° of each other June 18. They have not passed this close in the evening sky since 2006.

This 9th-magnitude object rides high in the south on June evenings as it traverses the sparse star fields of eastern Coma Berenices.

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