Skip to main content (Press Enter).
Official Website of the United States Navy
Mission & Vision
Naval Oceanographic Office
Fleet Numerical Meteorology & Oceanography Center
United States Naval Observatory
News from the Naval Observatory
Earth Orientation Department
USNO Earth Orientation Products
Contents of Bulletin A
USNO GPS Products
GPS User Information
USNO VLBI-based Products
VLBI Correlator Data
VLBI-based Earth Orientation Parameters (EOP)
Earth Orientation Information Center
General Information about Earth Orientation
Frequently Asked Questions About Earth Orientation
What Is Earth Orientation?
What Is Polar Motion?
What does the Earth rotation coordinate measure?
What is the Celestial Pole Offset?
What is a Leap Second?
How do we measure Earth Orientation?
What causes variations in the Earth's orientation?
Who uses Earth orientation information?
Publications About Earth Orientation Products
Earth Orientation Software
Precise Time Department
The USNO Master Clock
The USNO Master Clock
Time Dissemination at the USNO
USNO Alternate Master Clock (AMC)
Cesium Atomic Clocks
Hydrogen Masers at the USNO
Rubidium Fountain Clocks
USNO Time Scales
International Time Scales and the BIPM
Definitions of Systems of Time
Global Positioning System
Global Positioning System Overview
USNO GPS Data Categories Explanation
CGGTTS Data Format
USNO GPS Time Transfer
GPS Information: SA, DGPS, Leap Seconds, etc.
GPS Week Number Rollover
GPS Timing Data and Information
USNO Format Explanation
USNO Computer Display Clocks
Two-Way Satellite Time Transfer (TWSTT)
Network Time Protocol (NTP)
US Eastern Time Zone NTP Servers
US Mountain Time Zone Servers
DoD Customer Servers
Astronomical Applications Department
Celestial Reference Frame Department
Senior Enlisted Advisor
Naval Oceanography Operations Command
Fleet Weather Center - Norfolk
Fleet Weather Center - San Diego
Joint Typhoon Warning Center
Public Use of Limitations
United States of America Department of the Navy Seal
The Sky This Week
U.S. Naval Observatory's Weekly Blog
Standing Under the Galaxy
by Geoff Chester, USNO Public Affairs
16 August 2022
The Summer Milky Way, imaged 2017 August 21 from Smith's Ferry, Idaho
with a Canon EOS Rebel T2i DSLR
We’ll be taking a few days off next week, so this week’s edition covers a few more days that usual.
The Moon wanes in the morning sky this week, climbing toward the rising stars of winter. Last Quarter occurs on the 19th at 12:36 am Eastern Daylight Time. If you are up before the Sun on that morning look for the Moon as she passes between the planet Mars and the Pleiades star cluster. This should present a beautiful photo opportunity for early risers. As Luna’s crescent gets slimmer over the next several days, watch her move from the bright stars of Taurus into Gemini.
The nights of late August have always been some of my favorites for stargazing. The first hints of dry autumnal air begin to push the heat and humidity of July farther south, while the time of evening twilight falls at a more reasonable hour. I can still observe in light clothing surrounded by the sounds of crickets and katydids chirping in the night. The best part is the splendor of the summer sky, cleaved by the hazy band of the Milky Way. It’s a time when I am often on vacation, either at the shore of the mountains, but almost always away from city lights. I will often spend the first half hour of my evening sessions just looking at the Milky Way with my unaided eyes. Not only does this give me a relaxing way to let my vision adapt to the dark, it also helps me once again to understand my singular place in the cosmos. The luminous band that arches across the summer sky is the subject of much sky lore, and we find references to it in countless records left by our forebears.
At this point in the evening I will often pull out my binoculars for a tour of our home galaxy, starting at the southern horizon with the distinctive constellation of Scorpius. This is one of the few constellations that resembles its namesake, and it is one of the oldest star patterns that have survived in lore and legend over millennia. A stone mace-head that dates to around 3500 BCE depicts the Scorpion leading an early Egyptian king in a ceremony marking the start of the annual Nile flood. The Scorpion’s “tail”, which resembles a giant fish-hook, plays a pivotal role in ancient Polynesian creation legends. It is also a treat for the eyes with striking color contrasts among its component stars.
Casual “sweeping” along the Milky Way with binoculars will reveal dozens of knotty concentrations of light as well as mysterious dark voids that seem bereft of stars. These so-called “dark nebulae” formed constellations in ancient Inca sky lore, but today we know that they are vast opaque clouds of matter that will ultimately lead to the formation of star clusters and bright nebulae like the brighter knots that dot the luminous band.
Soon, however, I will start viewing the Milky Way’s brighter patches with my telescope. Sometimes these knots resolve into dozens to hundreds of sparkling pinpoints or softly glowing wisps that resemble wafts of luminous smoke, and often I will see both together. Many of them have wonderful names bestowed on them by astronomers of bygone days, and it’s always fun to scan objects with names like the Lagoon, Trifid, and Swan Nebulae or the Wild Duck, Caroline’s Rose, and Double Clusters.
As the night turns to morning the Milky Way bisects the sky. East of the galaxy are the dim constellations of autumn, which this year are punctuated by the glow of two distant giant planets. Saturn is the first to rise and may be seen low in the southeast as evening twilight ends. By midnight the ringed planet nears the meridian and is in prime position for a long look through the telescope. Closer to the eastern horizon you will see the much brighter glow of Jupiter, which will reach opposition in late September. These two distant worlds will continue to attract our attention for the rest of the year.
Ruddy Mars is still best seen before sunrise. The red planet spends the week drifting eastward near the bright star Aldebaran and the Pleiades star cluster. He will be joined by the waning Moon on the morning of the 19th. The trio will make for a fine naked-eye sight for early risers on the 19th and 20th.
DoD Accessibility/Section 508
No Fear Act
Plain Writing Act
Veterans Crisis Line
DoD Safe Helpline
Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529
Official U.S. Navy Website