What's in the Sky: Great nights of stargazing ahead this September

Fall arrives on Sept. 22, the autumnal equinox. The Sun will lie directly above the equator, and we’ll have approximately the same amount of day and night length.

Venus is still in the evening sky, but just barely. Look for Earth’s neighbor very low in the west, just before sunset. Through a telescope, it will appear as a slight crescent shape. Venus is drawing closer to us, and will soon pass between Earth and the Sun. By late October, we’ll be able to see Venus again, but now it will be in the morning sky. Mercury will be to the right of Venus for most of the month, but even harder to see, as it will be quite close to the Sun.

Saturn made its appearance in the evening sky last month, and will be in much better position to view in September. The ringed planet rises at about 9 p.m. at the start of the month, and by about 7 p.m. at month’s end. It will be easy to spot, a bright “star” low in the east, with no other real bright stars around it. Saturn will be yellowish-white, and will not twinkle much at all. Pretty easy to pick out. Train even a small telescope on Saturn and you can see its magnificent rings.

To the right of Saturn, in September skies, lies the planet Neptune. The solar system’s outermost planet will be at its closest to us on Sept. 25. That’s still not very close, some 2.68 billion miles away! Neptune is so far away that it takes about 165 years to complete an orbit. Neptune’s existence was predicted before it was seen, based on irregularities of the orbit of Uranus. A French mathematician predicted the mass and location of the planet, and gave them to an astronomer at the Berlin Observatory, who discovered the planet the first night of searching, in 1846.

The International Space Station (ISS) will make some nice overhead passes in September. For some good times, go to Heavens Above (heavens-above.com) and enter your location in the upper right of the screen. Then, on the main screen, look for “10-day predictions for satellites of special interest” and choose “ISS.”

Here is a fun exercise to try. The late Steve Stout, the original Director of the Goldendale Observatory, always liked to give his age in “lunations” rather than years. What is a lunation? It is simply the time it takes for the Moon to go through its complete cycle of phases, the exact time from one New Moon to the next. It averages 29.530589 days. So, determine how many days you have been alive, and divide that number by 29.530589 to get your answer. A simple way to estimate how many days you have been alive is to multiply your age by 365.25 (which accounts for leap years), and add the days since your last birthday. Then, divide the total by 29.530589 to get your answer. Mine comes out to 979 lunations. If math gives you a headache, you can find calculators on the internet that will give you the answer.

Enjoy the night skies of September!