Naked Eye 100 Challenge

Amateur astronomers love lists… The Messier observing list, the Hershel 400, the Hershel II, and on. Some lists can be complete on a night or two, some lists may take years, or even a lifetime to accomplish. Amateur astronomy is not the only avocation to use lists like this. Birders attempt to see all of the birds known to occur in their home country. Aircraft spotters love to see each model of aircraft in the air. Divers keep lists of species seen underwater.

Rainbow Wheel
A rainbow and cloud shadows produce a rainbow wheel
Lists like these are not only fun, but allow the list chaser to sample the wonders our universe has to offer. The challenge of finding and observing each of the items is worthwhile. Each object is a lesson into the science, hunting each object allows skills to be practiced.

Most of the astronomy observing lists require a small telescope to accomplish, or at least a pair of binoculars. One list is a bit different, it does not require any optical aid at all… The Naked Eye 100.

The first list for 100 naked eye objects was put together by Arizona amateur astronomer Joe Orman. Many of the items on the list are quite poetic… moonlight on water, a glitterpath, fall asleep while watching the sky. These are things all of us should see and do, just to appreciate a beautiful world.

I like Joe’s list, but do have a few small quibbles with it. Mostly it is just too easy, I have pretty much completed it, with the exception of the uncommon solar halos or an annular solar eclipse. Thus for my own uses I have modified his list to create my own Naked Eye 100. This is a personal list with quite a few substitutions from Joe’s… There are some more uncommon phenomena I have added, removing some items from the original 100 to make room. Some items I expanded upon, there are several types of mirages and some variations on the rainbow. Many of the phenomena can be referenced on the excellent Atmospheric Optics website. I am afraid my list is not nearly as poetic as Joe’s, but it is much more challenging.

The rules… All of these items should be observed without the aid of any optical magnification, no telescopes or binoculars. A few of the items are not truly naked eye for reasons of safety… In particular the solar events will require the use of appropriate filters for solar viewing. This includes Mercury and Venus transits, a partial solar eclipse and naked eye sunspots. Eyeglasses or contacts are likewise allowed if the individual normally requires their use. In general, these are events that should be visible to anyone who simply makes an effort to observe the natural world.

The list is not fixed, I am open to suggestions to improve it. Is there something missing that should really be on the list?

I have been working on the NE100 for a couple decades now, and it may be as long before I complete it. In the process I have seen and learned so much.

The Naked Eye 100 Challenge v1.0

1 Sunrise Watch the Sun rise, from the first glow to the Sun itself rising over a distant horizon   ✓
2 Equinox Sunrise At equinox the Sun rises due east. Look along an east-west aligned street, canal, etc.   ✓
3 Crepuscular Rays Brilliant streaks of light radiating from clouds or mountians backlit by the Sun   ✓
4 Anticrepuscular Rays Crepuscular rays converging on the antisolar point, often very faint and diffuse   ✓
5 Belt of Venus & Earth’s Shadow A rising pink band of light visible at sunrise and sunset, the edge of the Earth’s shadow   ✓
6 Midnight Sun Watch as the Sun never sets above the arctic circle in summer  
7 Sunset Watch our closest star set, but keep watching afterward for the best sky and cloud colors   ✓
8 Moonrise The rising Moon silhouetting a distant mountain, tree, or saguaro cactus is an awe-inspiring sight   ✓
9 Crescent Moon On evenings after new Moon, look for the delicate crescent above the twilight horizon after sunset   ✓
10 Earthshine Sunlight reflected off the earth onto the dark side of the Moon, best when the Moon is thin crescent   ✓
11 Moonset Whether full Moon or crescent, the last bit to slip beneath the horizon always brings a special sadness   ✓
12 Sunspots Occasionally sunspots get big enough to see without magnification. Use proper eye protection!   ✓
13 Partial Solar Eclipse The Moon obscuring part of the Sun, use proper eye protection!   ✓
14 Total Solar Eclipse Within the path of totality, the Moon completely covers the Sun, revealing the beauty of the Sun’s corona   ✓
15 Bailey’s Beads Sunlight peeking between the mountains of the Moon during a total solar eclipse   ✓
16 Diamond Ring A brief flash of direct sunlight signals the beginning and end of a total solar eclipse   ✓
17 Annular Solar Eclipse Near apogee the Moon’s apparent size is not enough to cover the whole Sun during an eclipse leaving a bright ring  
18 Partial Lunar Eclipse When our Moon partly enters the Earth’s inner shadow, the umbra   ✓
19 Total Lunar Eclipse When the Moon completely enter the Earth’s inner shadow becoming a deep red or copper color   ✓
20 Transit Of Mercury There are 13 or 14 transist of Mercury each century, the next is in May 2016   ✓
21 Transit Of Venus These occur in pairs every 120 years, last occured in 2012, the next is in Dec 2117   ✓
22 Mercury Every other month or so Mercury is visible well above the glow of either dawn or sunset   ✓
23 Venus Brightly visible above the morning or evening twilight for several months at a time   ✓
24 Venus in Daytime Easy to see if you know where to look and can focus your eyes at infinity. It helps if Moon is nearby   ✓
25 Mars Near opposition, Mars is a brilliant object in the night sky   ✓
26 Jupiter Looks like a bright star, magnification needed to see the 4 Galilean moons   ✓
27 Saturn Looks like a bright star; magnification needed to see the rings   ✓
28 Asteroid The brightest asteroid Vesta is just visible at opposition   ✓
29 Near Earth Asteroid Rare, but possible, on April 13, 2029, asteroid 2004MN will make a close naked-eye pass  
30 Comets Every year or so one reaches naked-eye visibility. Even rarer are bright “Great Comets” like Hale-Bopp   ✓
31 Comet in Daytime A few times a century a comet will be bright enough to see in a sunlit sky   ✓
32 Planetary Conjunction Look for 2 or more planets appearing near each other   ✓
33 Star&Planet Conjunction Occasionally planets appear very close to background stars   ✓
34 Moon&Planet Conjunction Venus is the crescent Moon’s most noticeable companion, but look for other planets near the Moon too   ✓
35 Lunar/Stellar Occultation Antares, Regulus, Aldebaran and Spica all lie near the ecliptic and are occasionally covered by the Moon   ✓
36 Lunar/Planetary Occultation Occasionally the Moon also passes in front of one of the planets   ✓
37 Ecliptic The Sun, Moon and planets make a straight line across the sky — the plane of our Solar System   ✓
38 Zodiacal Light A pale cone of light along the ecliptic; best seen before dawn in the fall or after sunset in the spring   ✓
39 Zodiacal Band A band of zodiacal light across the entire sky   ✓
40 Gegenschein A faint patch of light on the ecliptic; look at the antisolar point around midnight   ✓
41 Aurora Borealis or Australis Energetic solar particles striking our atmosphere and causing colorful displays   ✓
42 Airglow A faint glow from air itself seen on the darkest of nights   ✓
43 Sun Halo On winter days with thin clouds, look for a complete circle around the Sun, 22 degrees in radius   ✓
44 Moon Halo Same as a Sun halo, but seen around the Moon at night   ✓
45 Sundogs (Parhelia) Appear in thin clouds as bright colored patches 22 degrees to the left and right of the Sun   ✓
46 Sun Pillar Vertical column of light above Sun when Sun is on horizon; formed by reflection off ice crystals   ✓
47 Other Halos Circumzenithal arc, tangent arcs, Parry arc, 46-degree halo — some are subtle and rarely seen  
48 Light Columns Columns of reflected light from bright ground sources  
49 Corona In thin clouds, colored rings a few degrees across around Sun or Moon   ✓
50 Aureole Bright glow around the Sun or Moon, colorless and only a few degrees across   ✓
51 Glory Looking into fog or clouds from a plane or mountaintop, colored rings around the antisolar point   ✓
52 Spectre Of The Brocken Your own shadow in the center of the glory   ✓
53 Mountain Shadow From the top of a mountain, look opposite the sunset; perspective makes a cone-shaped shadow   ✓
54 Irisation (Iridescent Clouds) Multi-colored patch in thin clouds or on cloud edges many degrees from the Sun   ✓
55 Noctilucent Clouds Rarely-seen clouds of ice particles at the edge of space after twilight, seen only from high latitudes   ✓
56 Nacreous Clouds Bright stratospheric ice clouds seen at a low Sun angle   ✓
57 Rainbow The primary rainbow appears as an arc 42 degrees in radius centered around the antisolar point   ✓
58 Double Rainbow The outer, or secondary, rainbow is 51 degrees in radius. Colors are reversed   ✓
59 Reflection Bow A second rainbow caused by reflection off water  
60 Red Bow A rainbow cast by the last reddened light of sunset   ✓
61 Moonbow A rainbow illuminated by moonlight   ✓
62 Fogbow A rainbow in a fogbank   ✓
63 Alexander’s Dark Band A darkened band between double bows   ✓
64 Wheel A combination rainbow and crepuscular rays   ✓
65 Superior/Mock Mirage A mirage caused by a temperature inversion near the surface   ✓
66 Inferior Mirage A mirage caused by a warm layer at the surface   ✓
67 Fata Morgana An usually strong and complex form of a superior mirage   ✓
68 Etruscan Vase/Omega Sun The setting Sun distorted by mirage at the horizon   ✓
69 Green Flash The upper limb of the Sun flashes green just before setting   ✓
70 Blue Flash A more extreme form of the green flash that fades to blue  
71 Lightning Lightning is an awesome sight day or night, but use caution and observe from a safe distance!   ✓
72 Sprites or Jets High atmospheric forms of lightning, usually seen above thunderstorms  
73 Milky Way Our own galaxy seen edge-on, this faint band crossing the sky is the combined light of billion of stars   ✓
74 M24 Star Cloud A thick cloud of stars above Sagittarius   ✓
75 Andromeda Galaxy The most distant object visible to the unaided eye, 2.5 million lightyears away   ✓
76 Magellanic Clouds A pair of dwarf galaxies near our own Milky Way, visible from southern latitudes   ✓
78 Pleiades A nearby open cluster easily visible as a tight group of stars in Taurus   ✓
79 The Coal Sack A dark nebula in Crux   ✓
80 The Pipe Nebula A group of nebulae in Ophiuchus   ✓
81 Omega Centauri The largest globular cluster in our galaxy, visible as a ‘fuzzy’ star   ✓
82 47 Tucane A bright globular in the southern sky  
83 Orion Nebula A bright nebulae in Orion just below the three stars of the belt   ✓
77 Eta Carina A bright nebula and supergiant star nearing the last stages of life   ✓
84 Sirius The brightest visual star in our skies in the constellation Canis Major   ✓
85 Polaris Directly over the Earth’s north pole Polaris seems not to move as our world turns   ✓
86 Variable Star Several variable stars can be seen to dim over the course of hours or days, try Algol or Lambda Tauri  
87 Nova Stars can suddenly brighten for a variety of reasons, every few years such an event is visible without a telescope   ✓
88 Supernova Rare, but possible, SN1987A was visible without a telescope  
89 Meteor Shower Make a point to watch one of the annual showers, find a dark sky and a comfortable place to watch   ✓
90 Sporadic Meteors Random meteors can be seen at any time in a dark sky, make a wish…   ✓
91 Bright Bolide A bright meteor that crosses the sky   ✓
92 Persistant Meteor Train A glowing cloud left behind by a meteor that can last for many minutes   ✓
93 Meteoric Flash An exploding meteor bright enough to light up the landscape   ✓
94 Meteor Storm More than 1,000 meteors per hour flashing across the sky   ✓
95 Artificial Satellites Many artificial satellites are easy visible each evening and morning   ✓
96 Iridium Flares Flash that lasts several seconds; like a slow-moving meteor. Check for visibility.   ✓
97 Rocket Trails A rocket launch can be seen from hundreds of miles away, better yet if they occur just after sunset or before dawn   ✓
98 Rocket Launch Observe the launch of a space mission  
99 All-Night Sky Stay up all night and watch the sky change as the earth turns   ✓
100  Fall Asleep While Watching the Sky Make your bed under the open sky. Lie back, look at the stars, close your eyes and dream of infinity   ✓

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

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