Skywatch July 2016

Skywatch July 2016

In July 2016 we are able to see all five ‘naked eye’ planets in the sky, a mere six months after the last time this happened. (Prior to winter 2016, it had been a decade since all the visible planets could be seen at one time.) Our overhead sun returns in July throughout the islands. We enter the heart of summer as such classic starry patterns as the Summer Triangle and the Scorpion glisten in the July evening sky.

Planets in July

Venus and Mercury together at dusk

Venus returns to our skies in late July after ten-week absence behind the sun. However, while Venus is the brightest dot in the sky, it will be tricky to find this summer. In late July you’ll only have 30 minutes from the time Venus appears at dusk, extremely low in the west, till the time it sets.

You can start looking for Venus around July 15. Around 7:30 p.m., scan the western horizon, and look for Venus a mere 5 degrees (roughly the width of two fingers at arm’s length) above the western horizon. It will be extremely bright (minus 3.9 magnitude), which will make it easier to spot; but make sure you are searching over a flat horizon or you’ll miss it. By 8 p.m., the planet will set.

Venus does a dance with the planet Mercury for the entire last two weeks of July. On July 15, Mercury is less than one degree to the right of Venus, less that the thickness of your pinky finger at arm’s length. Mercury shines at minus 1 magnitude, as bright as a very bright star.

Night by night, Mercury will appear a little higher above Venus. By the end of July, Mercury will be about eight degrees (four fingers) to the upper left of Venus, and will set by 8:15 p.m. The planet Mercury does fade in brightness from minus 1 in mid-July to zero magnitude at the end of the month; but since it does not set till 8:15 p.m. your odds of catching it do improve.

Mars, Saturn and Antares: the triangle continues

Throughout July 2016, look for the very distinctive triangle formed by Mars, Saturn and Antares, the brightest star in the Scorpion. While Mars’s brightness peaked in late May at a whopping minus 2.08 magnitude, it remains the brightest member of the triangle. Orange-white Mars shines at minus 1.4 magnitude in early July, which is a bright as the brightest star in the sky. As the earth pulls further and further away from the red planet, Mars does fade in brightness by 40 per cent by month’s end, shining at minus 0.8 magnitude. Still, Mars in late July is still brighter than any star except Sirius, which is itself missing in action till it returns to our morning skies in August.

The other two dots in the triangle are the planet Saturn, the second brightest dot at 0 magnitude, shining with its distinctive yellow-white color; and the star Antares, the least brilliant of the three dots at 1.03 magnitude, showing an orange glow that’s similar to much-brighter Mars. (Antares’ name means ‘the rival of Mars,’ due to the similarity in color.)

Throughout the month the three dots make a triangle; check out our July star map for their basic configuration. At the start of July look for the trio high in the south as it gets dark at 8 p.m., with Mars leading the way; the red planet is the point of a narrow triangle, with dimmer Saturn and Antares each about the width of two palms to the left of Mars. In early July the triangle hits the western horizon in the early hours of the morning, with Mars plunging below the horizon at 2:30 a.m. and then Saturn and Antares taking the plunge around an hour later.

As July goes on, Mars appears to draw closer to the other dots, Saturn and to Antares. By the end of July, we have a more compact triangle than we saw early in the month, with each dot separated from the others by the distance of a single palm. By the end of July, the triangle is due south at dusk. In late July, Mars sets a few minutes before 1 a.m., and the other two dots follow it down less than an hour later.


At the start of July, look for Jupiter halfway up in the west at dusk, setting at 11 p.m. The planet shines at minus 1.8. At the start of July, Mars and Jupiter will still seem rivals in brightness; but the end of July there will be no contest, as Jupiter shines nearly three times brighter than fading Mars. By month’s end, Jupiter is only about 20 degrees above the west at dusk, and sets around 9:30 p.m.

On July 8, looked for the slender crescent moon just below Jupiter.

Five planet-a-thon returns

In late January 2016 we were able to see all five naked eye planets in the morning sky at one time, for the first time in a decade. This phenomenon returns in late July, now in the evening sky. That said, the window to see all five planets is very narrow. You need to go out between 7:30 and 8 p.m.; with good weather conditions and a flat horizon, you will see Venus and Mercury huddled just above the western horizon. Then, look for Jupiter above Venus and Mars; and Saturn and Mars high in the south.

While there is a very limited time each day to see this planetary quin-fecta (between sunset and a half an hour after sunset), the phenomenon will persist from mid-July till the end of August. By late August, Jupiter will have joined Mercury and Venus, forming a triangle of planets sitting very low in the west at first darkness.

Other sky events in July

Lāhaina Noon returns

In the tropics the sun passes overhead twice during the year. On these two days, at local noon, the sun will be exactly overhead and an upright object such as a flag pole will have no shadow. This phenomenon only occurs in the tropics; the sun is never overhead in any other part of the planet. The northern reaches of the Hawaiian Islands, such as Midway Island, are north of the tropics and do not experience the overhead sun.

The dates of your ‘overhead sun’ in the Hawaiian Islands vary depending on how close you are to the topic of Cancer. The sun is directly overhead on the Tropic of Cancer (23.5 degrees north of the equator, and north of all of the main Hawaiian Islands) on June 21. Then, in Līhu‘e, Kaua‘i, overhead sun occurs on July 11, at 12:42 p.m. Further south, on the Island of Hawai‘i, the overhead sun date does not occur till July 24 (12:26 p.m. for Hilo, 12:30 p.m. for Kailua Kona). The overhead sun will occur on the equator on the first day of fall and also on the first day of spring; and will occur on the tropic of Capricorn (23.5 degrees S. latitude) on December 21.

The chart below gives the overhead sun dates for a number of locations in the islands.

2016 Lāhaina Noon Days and Times

LīhueJuly 11 12:42 p.m.
Kāne‘oheJuly 15 12:37 p.m.
HonoluluJuly 15 12:37 p.m.
KaunakakaiJuly 16 12:34 p.m.
Lāna‘i CityJuly 18 12:34 p.m.
LahainaJuly 18 12:33 p.m.
KahuluiJuly 18 12:32 p.m.
HanaJuly 18 12:30 p.m.
HiloJuly 24 12:27 p.m.
Kailua-KonaJuly 24 12:30 p.m.
South Point Island
of Hawai’i
July 28 12:28 p.m.


Southern Cross –absolute last chance!!

Generally, the first days of July are the last chance we have in the islands each year to see the Southern Cross (Crux). At dusk in late June and the first few days of July, look due south; you will see two brilliant stars just above the south horizon. The one on the left is Alpha Centauri; the one on the right, Beta Centauri. These are also called ‘The Southern Pointers.’ Draw a line to the right from these stars that’s about three times the distance between the two stars themselves. This will point you to Gacrux, the top star in the Cross. Look down to the horizon to catch the lowest star in the Cross, Acrux; then try to find the two stars that make the crossbeam. Make sure you have a flat horizon, such as the ocean.

After July 4, Crux gets lost behind the sun, and returns to the morning sky in December.

July star map

Like all of our monthly maps, this one is good for 10 p.m. on the first day of the month, 9 p.m. for the middle of the month, and for 8 p.m. at the end. One key constellation that’s missing in Orion. Orion vanishes into the sun every year in late May, and does not return to the predawn sky till late July.

The Big Dipper is halfway up in the northwest by map time. Due south we now have a good view of Scorpius (“Maui’s Fishhook” in the Hawaiian Islands), whose brightest star Antares forms a triangle with Mars and Saturn this summer. The summer triangle – three stars pulled from three different constellations – is rising in the east, with the brightest of the three, Vega, leading the way.

Moon phases (Hawaiian Time zone):

New: July 4
First Quarter: July 11
Full: July 19
Third Quarter: July 26

Coming soon!

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2017-06-05T12:05:26+00:00Monthly Astronomy Article|