Summer sky viewing: Hawai‘i has several advantages

There are several advantages that living in Hawai‘i brings to the hobby of sky-watching. First, we don’t have the extreme weather to contend with living in the tropical region of the Earth.

Those in the temperate zones are now celebrating the warmer conditions to view the sky, putting away their heavy jackets and thermoses of hot chocolate for the summer. Unless you are at the summits of Haleakala or Mauna Kea, you rarely have the need for winter gear here.

In addition, we don’t have to wait for the sky to get dark too much later in the evening. The difference in daylight hours in Hawai‘i can be as much as plus or minus two hours between winter and summer months as opposed to the Mainland, which can range from four to six hours, depending on the location.

Another benefit of our position on the planet is our view of the sky. From the equator it is possible to see all the stars from the north celestial pole to the south celestial pole. The further away from the equator you travel, you start to lose some of the sky in the opposite direction. In other words, we do not see approximately 20 percent of the southern sky (Hawai‘i is around 20 degrees north of the equator), and if you lived in Seattle you would not see about 47 percent of the southern sky.

Being located in the middle of an ocean has its benefits related to the sky as well. Air currents are generally smoother over water, causing less turbulence for the little photons of light reaching our eyes from space. Those same breezes keep the atmosphere above us relatively clear of aerosol pollutants too, as we all have experienced after a week of Kona weather.

On the subject of pollution, we also do not have as many problems of surrounding light pollution because the islands are relatively isolated from other nearby sources of light. Light pollution is one of the worst preventable causes of losing the night sky, as population centers grow and lights are added indiscriminately without any thought to the environment.

While lighting is necessary for safety and comfort reasons, lights should be shielded at the very least to illuminate areas efficiently instead of scattering the light in all directions, including up to the sky.

With all this in mind, take the time to appreciate the sky the season has to offer. The summertime sky is rich in star clusters and nebulae as the center of the Milky Way comes into view.

Satellite-watching is also great this time of year since the best time to see satellites are the hours just after sunset and before sunrise. Satellites become visible as sunlight bounces off the reflective surfaces of either the solar panels or the metallic shell of the object.

Spotting satellites requires some patience and a little bit of luck but it’s well worth it. As with meteors, the chances are better in darker locations. But it definitely does not move as fast as a meteor. A satellite will appear as a star-like point of light moving slowly across the sky, sometimes brightening or fading as it travels. As opposed to planes, satellites have no blinking lights or other lights of different colors and generally look much smaller and farther away.

Identifying a satellite is even more challenging, although not impossible. It’s easier to know what you are looking for before you look for it rather than trying to find out what the satellite was after you saw it.

Hundreds of satellites surround our planet, including the International Space Station, and you cannot see all of them all the time. One of the best Web sites for satellite-searching is www.heavens-above.com. By plugging in your location, you can search for the dates and times of the brighter objects like the Space Station, and download sky maps for the passes. Make sure you look for passes that are magnitude +1, 0 or in the negative numbers. (The “smaller” the number, the brighter the object)

Iridium flares are also popular. Iridiums are communication satellites with mirror-like panels that flash swiftly and brightly in the sky. They are also fairly reliable. While I would recommend checking the Web site just prior to going out to spot the Space Station (because of changes in its orbit), Iridiums are usually right where and when they are supposed to be. You can impress your friends by pointing to the sky and “predicting” the pass of a satellite in orbit.

Here is information about the planets:

Earth

Earth is at aphelion, or the farthest point in its orbit around the sun, 94.5 million miles as opposed to 91.4 million miles at the closest point in January. The difference in the distances is 3.4 percent.

Mercury

By the first week of July Mercury has reappeared in the morning sky, but it will be another week before it can be seen easily. The tiny planet sits above the raised arm of Orion and below the feet of the Gemini twins, appearing at its highest above the eastern horizon on July 20.

Venus

July starts off with Venus and Saturn close together in the evening sky. During the first week of the month you can watch the two planets slowly start to pull away from each other as Venus nudges toward the bright star Regulus (in Leo) to the east, and Saturn sinks toward the west. On July 16 a new crescent moon can be seen between the separating pair. Venus is at its brightest this month as it passes us on the inside track of its orbit around the sun.

Mars

Mars is still in the morning sky, rising by 2 a.m. in early July and at 1 a.m. at the end of the month. But at least it’s beginning to get brighter as we slowly catch up to the Red Planet in its orbit. As the summer turns to fall and winter, watch Mars get bigger and brighter as it heads toward opposition in December.

Jupiter

While Venus lights up the western sky at dusk, Jupiter rules the east. The giant planet is not as bright as smaller Venus, but then it is over 300 million miles further away from us. At the beginning of July it’s already halfway up in the eastern sky at sunset, near the constellation Scorpius.

Saturn

This is Saturn’s last month to shine in the evening for a while — by next month it will be low in the west at sunset and difficult to spot.

The next time we can see Saturn easily again will be around mid-September when it appears in the morning sky ahead of the rising sun.

Moon phases

Third Quarter: July 7

New Moon: July 14

First Quarter: July 21

Full Moon: July 29

• Questions? Contact Carolyn Kaichi @ hokupaa@bishopmuseum.org or 847-8203.