May Stargazing at Great Basin National Park

Article by Jerry Hilburn

Great Basin National Park, designated a gold-tier International Dark Sky Park, offers one of the darkest and clearest night skies in the United States making it a prime location for stargazing. At the beginning of the month of May in 2024 the sky darkens by 9pm. The moon enters its waxing phase in the first half of May and begins rising to the west after 9pm on May 9th. The first half of May offers dark moon free evenings.

Most of the planets are only visible in the daytime skies, but if you get up before 5am you may be able to see Saturn, Mars, and Mercury rising to the east. Saturn will lead and be the brightest planet, Mars follows and will be a redder hue, and Mercury will be bright but tiny and close to the horizon where the sun rises. The moon is waning and will soon hide in the daylight for a week.

Figure 1 - Early Morning Planets

The absence of visible planets in the spring evening sky offers aspiring astronomers a unique chance to familiarize themselves with the constellations of spring and their related navigational stars.

In celestial navigation, fifty-seven navigational stars, along with the star Polaris, are accorded special significance. Out of around 6,000 stars that can be seen with the naked eye when conditions are perfect, these chosen stars stand out for their brightness and cover 38 constellations across the celestial sphere, ranging from a declination of −70° to +89°.

The names of many of these stars date back to ancient times, having been named by civilizations such as the Babylonians, Greeks, Romans, and Arabs.

Let’s begin our evening of observation by finding the Big Dipper. This constellation is among the easiest to spot as it looks like a large pot and can be found almost directly overhead in May.

Facing North, see if you can find the Big Dipper which should be located directly overhead.

Figure 2 - Big Dipper

In the time of the early Romans, two dim stars from the Big Dipper, Mizar and Alcor (located closely together), served as an ancient eye test. If an individual could see these close stars, they would have been eligible to be an archer in the Roman army. The test involved looking at each of the stars of the Big Dipper and identifying the one with two close stars (Mizar). This served as a way to assess the eyesight of individuals and potentially sort warriors between officers and non-officers based on their visual acuity.

Test your eyesight by facing North and finding Mizar in the Big Dipper. Do you see a small faint star at the top left edge of Mizar? If so, you might have qualified to be an archer or officer in the Roman legions.

Polaris
Facing North the next constellation on our spotting list is the Little Dipper (Figure 3). This asterism contains the most important navigation star in the Northern Hemisphere, Polaris. Polaris lies nearly in a direct line with the Earth's rotational axis "above" the North Pole. Polaris appears motionless in the sky as the stars of the northern sky appear to rotate around it. Therefore, it makes an excellent fixed point from which to draw measurements for celestial navigation and for astrometry .

Figure 3 - Little Dipper

Another interesting use of this constellation by visual astronomers is in providing a method of determining magnitudes visually. In the cup of the little dipper the four stars starting with Kochab at magnitude 2, decline in brightness in one magnitude steps. Visual astronomers in the North use this bucket to find visual magnitudes of other stars in the skies through comparison of the bucket stars. See if you can spot all four stars in the bucket, and also know how to find Polaris. Knowing how to locate the pole star can be a life saver when lost at sea, or on land.   

Ecliptic Plane
As spring transitions into summer, looking southward reveals the progression of constellations named after astrological signs moving along the ecliptic plane. In Figure (4) the red line that extends from the southeast to the northwest depicts this plane, highlighting the asterisms that track along it throughout the night. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars. During May the following constellations are visible along the red line and move from the east to the west through the night.

Libra - Evening

Virgo - Evening

Leo - Early Evening

Cancer - Early Evening

Gemini - Early Evening

Figure 4 - Facing South along the plane of the ecliptic

In the early hours of the morning the following constellations rise as the plane sinks south, making them a bit difficult to find if obscured by trees or mountains. They are low on the southern horizon.

Aquarius - Early Morning

Capricorn - Early Morning

Sagittarius - Early Morning

Figure 5 - Morning Ecliptic

Navigation Stars

And now for the grand challenge. All of the visible navigation stars in May are shown in the following star chart. Step away from the campfire and move to an open area to look up! Using either of the 2 charts and a small pen light for assistance, see how many of the nav stars you can find in the night sky. Start with Polaris when facing North and this will help you orient your way across the night sky. Great Basin National Park offers the best conditions for visual observations and this aspect of the park offers hours of evening fun.

Facing North

Facing South

We hope you have clear dark skies during your visit!

All images were taken using Stellarium which is a free planetarium program available on Mobile and Desktop. Learn more at https://stellarium.org/en/