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.

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 heavens-above.com 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	✓