what magnitutude is star to see with naked eye?

University Lowbrow Astronomers
Naked Center Observer's Guide

by Dave Snyder
Written: February, 2000
Revised: September, 2005

This page has a variety of suggestions for beginning apprentice astronomers who wish to detect the heaven with only the unaided eye. It is a common misconception that you need to take a telescope to do astronomy; this only is not true. A wide multifariousness of objects tin can be seen with the naked eye: from planets and stars, to nebulae and galaxies. While you can ordinarily see more than detail if you use a telescope (or binoculars) and y'all tin normally see more objects of a given type if yous use a telescope (or binoculars); the same types of objects that can be seen with a telescope can be seen without a telescope.

If y'all've decided you want to observe the night sky without a telescope, y'all will demand some thought of what to look for. Fifty-fifty if y'all take a telescope or have made a house decision to purchase a telescope, information technology is a good idea to look at the sky without optical aid. The time you lot spend will give you ideas on where to expect and what to look for in a telescope. It will also enhance your observing skills.

Magnitudes

Some things are brighter than others: Astronomers apply an extension of a system invented in the second century B. C. to describe brightness of objects. Most objects are assigned positive numbers: The larger the number the dimmer the object (magnitude three is dimmer than magnitude two). Very brilliant objects are assigned negative numbers; this is true of the sun, the moon, bright planets and the brightest stars. Again the larger the number, the dimmer the object (magnitude -2 is dimmer than magnitude -three).

Here are a few examples (note these are typical values, values may be larger or smaller under some conditions):

Magnitude -27	The Sun
Magnitude -12	The Full Moon
Magnitude -5	Venus (the brightest planet) at its brightest
Magnitude -1	Sirius and Canopus (the 2 brightest stars)
Magnitude six	The dimmest objects visible with the naked centre
Magnitude 10	The dimmest objects visible with binoculars
Magnitude 25	The dimmest objects on a photographic plate   produced with a big telescope

Every bit mentioned above, the dimmest object visible with the naked eye is typically magnitude half dozen.five. However this magnitude (chosen the magnitude limit) tin can vary. Many factors affect the magnitude limit:

• Student dilation - When you lot outset become outside at night from a brightly lite room, you lot probably non be able to come across anything except the brightest objects, simply if you look a few seconds or so, your ability to run across improves dramatically.
• Dark adaptation - When y'all are in the dark, your retina gradually adapts to the light level; most of this adaptation occurs in the first half-hour. Nighttime accommodation will not be consummate if there are bright lights; once established night accommodation can be lost very quickly if yous after encounter bright lights. If you lot need a flashlight, it is best to use a dim cherry light. Such lights are less likely to interfere with night accommodation.
• Light Pollution - Even if y'all find a site away from city lights, the site still may not exist that dark. You lot may meet a glow near the horizon. Large cities tin be seen equally such a glow as far as a hundred miles away. Smaller cities tin can be seen from tens of miles away. When there is a glow on the horizon, there is often stray light all over the sky and this stray light will reduce what you can run across.
• Snow - Meaning snow embrace can have the aforementioned result equally lite pollution and tin reduce your limiting magnitude.
• Clouds - Consummate deject comprehend tin can foreclose yous from seeing anything, partial deject embrace oftentimes reduces the limiting magnitude.
• The Moon - The low-cal from the moon reduces your power to dark adapt. The limiting magnitude is larger (dimmer) when the moon is not visible.
• Altitude - Objects close to the horizon oftentimes are obscured in haze. Thus the limiting magnitude is smaller near the horizon than it is near the overhead point.
• Experience - Someone who has observed for many years typically can see objects one magnitude dimmer than an inexperienced observer.
• Historic period - As nosotros get older, our retinas become slightly less responsive, yet this will only be a few tenths of a magnitude. The effect of feel is more of import than the effect of age.
• Alcohol - Alcohol depresses the dark accommodation response.
• Nicotine - Cigarettes and other sources of nicotine also depress the dark adaptation response.
• Object Size - Extended objects (like galaxies or nebulae) are often harder to see than objects that appear to be points of light (like stars) if both objects have the same magnitude.
• Object Color - The limiting magnitude for red objects is lower than the limiting magnitude for objects of other colors.

For information nearly calorie-free pollution and what you can do about it.

Observing Sites

The first pace in astronomical observing is selecting an observing location. If you planning to observe bright objects, such every bit planets, it may be best to pick a site that is convenient, such as a identify close to home. If you are planning to observe dim objects you should pick an observing site that maximizes your limiting magnitude. It often helps to observe nigh the time of the new moon, and so the moon doesn't drown out the light from dim objects. In many cases it is helpful if at that place is a adept horizon; such a location will have few obstructions such every bit hills, mountains, copse or buildings. It is too a very expert idea to abstain from alcohol and nicotine earlier and during an observing session.

The limiting magnitude at suburban locations is typically iii.v, and the limiting magnitude at dark sites is typically six.5. Experienced observers at very nighttime sites accept reported limiting magnitudes as high as viii.five.

Constellations

If you want to find your style around the sky, y'all need to larn the constellations. Constellations are groupings of stars created by astronomers; many of the modern constellations were borrowed from constellations invented past ancient peoples. The existing constellations are not always the best groupings possible; there are many groupings of stars that seem like they should be constellations, but are not. Such groupings are called asterisms.

Which constellations are visible vary depending on your latitude, the time of day and the time of year. In full general, at a given location, some constellations volition always exist visible (they are called circumpolar), some are visible part of the time, and some are never visible.

Ane mode to acquire constellations is to first larn a few landmarks. The best landmarks vary depending on time of nighttime and the flavour, in the Northern Hemisphere the following are good choices:

Flavor	Season	Landmark
Winter Evening	Autumn Morning	Orion
Spring Evening	Wintertime Morning	Big Dipper
Summertime Evening	Spring Morning	Summertime Triangle
Autumn Evening	Summer Morning	Great Square of Pegasus

Each landmark tin can be used to locate other stars and/or constellations. (Notation: Orion is a constellation; however the Big Dipper, the Summer Triangle and the Great Square of Pegasus are asterisms. The indicated times are not the only times these landmarks are visible; for instance the Large Dipper is circumpolar from almost Northern Hemisphere locations, it is visible at all times. Notwithstanding spring evenings and winter mornings are the best fourth dimension to use the Big Dipper equally a landmark.) As y'all acquire the constellations, watch out for asterisms that look like to constellations; if y'all are not conscientious y'all will notice the sky filled with "large dippers" or "great squares." Try not to go past shape alone.

For more information on using landmarks to locate constellations, become to Introduction to the Constellations.

For on-line data on the constellations, get to Dibon Smith: The Constellations.

Finding Your Way Around

To notice your way effectually the nighttime sky, you probably volition find a star chart helpful. Yous have several choices:

• A uncomplicated device called a planisphere shows the bright stars and constellations and tin be adjusted for different seasons. Planispheres generally testify stars down to magnitude 4.v; this can be helpful if you are starting to larn the constellations, but you lot generally demand more item if you lot are looking for specific deep heaven objects.
• Astronomy magazines often accept star charts that are valid for the electric current month, again showing stars down to about four.5.
• Abrams planetarium (at Michigan State University) sells monthly star charts for a nominal fee.
• Star charts are available every bit books and come up in a variety of magnitude limits. If you lot are simply starting we recommend a volume with charts with magnitude limit 5; equally you gain feel you may want to get more detailed charts with magnitude limit half dozen or college.
• If you lot own a computer, you tin purchase programs that will produce star charts for whatever fourth dimension and whatsoever location; in most cases the magnitude limit can be adapted to suit specific needs.

Star charts may be somewhat confusing at start; they never look exactly like the night sky. However, this confusion will disappear one time you get used to them.

• Almost star charts have north up, eastward to the left and west to the right; a mirror image of most terrestrial maps. To align the chart to the night heaven, you need to observe n; in the Northern Hemisphere you can use the Big Dipper to locate Polaris, which is very close to due Northward.
• To gauge angles in the sky, the altitude from the horizon to the overhead point is 90 degrees and your fist held at arm's length is approximately 10 degrees. Using these estimates, if you know that information technology is 5 degrees from one star to some other star, you should be able to "hop" between the ii stars easily.
• The sky appears to be a curved dome, but charts are more often than not flat. This tin be confusing if you attempt to star hop from a star on one side of the heaven to star on the other side of the sky. This is less of a problem if you star hop brusque distances.
• Unless you have an upwardly to date chart from a magazine or a reckoner programme, at that place are likely to exist bright "stars" that appear in the sky, but practise not show upwardly on the nautical chart - they could be planets or transient objects such as comets. There are several ways to tell the difference between stars and planets. Stars tend to "twinkle" and planets generally do non twinkle. This frequently (just not always) allows you to distinguish stars and planets. Planets are always found along an imaginary line called the ecliptic. Mercury, Venus, Mars, Jupiter and Saturn are all brighter than any of the stars along the ecliptic.
• It is unlikely the limiting magnitude of the chart volition match the limiting magnitude of the night sky, so the chart may prove stars that are not visible in the heaven, or more likely, the sky may have stars that practise not appear on the chart.
• You may be tempted to bring a flashlight and then you tin read star charts in the night. Nevertheless to preserve your night accommodation, it is best to use a lite that is designed for astronomy: the best ones emit a dim cherry-red light.

For more data:

• How to brand a Planisphere (by Peter Alway).
• For suggested books and magazines go to the Lowbrow Astronomers Astronomy Bibliography; Introductory Texts.
• To obtain the Abrams Planetarium Sky Calendar, go to Abrams Planetarium (Michigan Land Academy).

The Planets

Venus, Mars, Jupiter and Saturn are like shooting fish in a barrel to observe with the unaided heart. Each planet is visible within a stock-still schedule. For a given evening, each planet may be visible the unabridged evening, but function of the evening or not be visible at all. This schedule doesn't change by much over the course of an evening or two, but will change over a period of weeks or months. Over the class of the yr, each of these planets will be visible at least part of the time. It is not possible to see any detail on these planets without a telescope.

Whenever Venus is visible, it is much brighter than anything in the sky with the exception of the sun and moon. Mercury, Mars, Jupiter and Saturn are brighter than annihilation other than Venus, each other, the sun or moon, Sirius and Canopus.

There are several things you can notice if yous observe planets over an extended menstruation of fourth dimension. Some planets brandish noticeable changes in brightness over the class of time. This is peculiarly truthful of Mars: sometimes it is well-nigh every bit brilliant as Venus simply can get as dim every bit magnitude +2. When Mars is bright, it is bright red; when it is dim, information technology is a pale pinkish (at such times it may be hard to run into any colour at all). Mars goes from bright to dim dorsum to bright every two years. Changes tin be observed in the other planets, just they are less obvious. All planets move relative to the groundwork stars, merely Mars, Jupiter and Saturn will occasionally appear to go into "retrograde" motility (they commonly move in a preferred direction, only occasionally they reverse direction, move in that direction for a time, reverse direction again and move in their preferred direction).

While Mars, Jupiter and Saturn all take satellites (moons), simply the four brightest satellites of Jupiter are vivid enough to be seen with the unaided eye. However even these satellites are almost incommunicable to detect in practice (without binoculars or a telescope) since they virtually always go lost in Jupiter'due south glare.

To observe Mercury, you must plan alee. The best opportunity to discover Mercury is when it is close to maximum elongation (that is, the planet appears at its highest point in the sky). It also helps to observe from a location without obstructions (such as buildings, trees, hills or mountains) in the management of the sun. Given the correct conditions Mercury will be very bright and tin be seen with the naked eye.

When Mercury is visible, you have just a short period of time to detect it. Sometimes Mercury is visible in the evening. In this case you tin start observing Mercury presently after sunset but you will accept less than an 60 minutes until the planet sets below the horizon. At other times Mercury is visible in the forenoon. Y'all will be able to run into Mercury at nearly an hour or and then before sunday rise and can discover it until the light from the rising sun drowns information technology out. Note: the amount of time that Mercury is visible depends on the position of Mercury in its orbit, the elongation and your horizon; Mercury may be visible for but a few minutes or may not exist visible at all if your horizon is poor.

Both Venus and Mercury occasionally pass between the Globe and the Sun, such an event is called a transit (for more information on transits, see the next section "The Sun").

Uranus is bright enough to be seen with the unaided eye, but appears as a dot of light that can be very difficult to distinguish from nearby stars.

Neptune and Pluto are as well dim to exist seen with the naked centre.

On occasion a planet passes in front of a star or the moon passes in forepart of a planet, such an event is called an occultation. Occultations tin can be predicted in advance and are like shooting fish in a barrel to observe if you plan ahead. Notation, the timing of an occultation depends on your verbal location. A given occultation is visible from some locations on the world and not from others.

It is often possible to run into planets during the daytime. The fob is to know exactly when and where to look. Venus is the easiest to locate, other planets are harder.

For more information:

• General information almost currently visible planets and other naked eye events can exist found at Star Hustler (Jack Horkheimer: Director of the Miami Planetarium) and at Abrams Planetarium (Michigan Country University).
• Information about occultations can be establish at the International Occultation Timing Association.

The Dominicus

Several solar phenomena are visible with the naked eye. Alarm: it can be dangerous to discover the phenomena described in this department. If you do non have proper eye protection you may suffer permanent heart damage. It is safe to observe the sun at sunrise and sunset provided y'all do so without magnification. However observing the sunday with binoculars or telescopes is specially dangerous, this can damage your eyes and your binoculars/telescope. This is true even at sunrise/dusk. Sunglasses and smoked glass are not adequate protection. These phenomena include sunspots, solar eclipses and Venus transits (a transit is where a planet passes betwixt the sun and the globe, the planet can be seen as a black dot on the lord's day'southward disk).

Observing sunspots is relatively easy. During solar maximum, which occurs in one case every eleven years, sunspots are ordinarily quite numerous. At such times, if you have proper eye protection, it is possible to see sunspots (no magnification is needed). (Eye protection is unnecessary at sunrise/sunset provided you use no magnification). At solar minimum (which also occurs every 11 years), there are by and large very few sunspots visible.

Observing a solar eclipse requires planning ahead. Eclipses occur infrequently: in a given year there may be every bit few as two solar eclipses or as many every bit five. A given eclipse is visible only in some parts of the earth. Some solar eclipses are fractional (the moon covers simply part of the sun'due south disk) and others are total (the moon covers the sun's unabridged disk). If a solar eclipse is total, totality tin merely be observed for locations on the globe within a narrow band which is at nearly 170 miles or 270 kilometers wide but thousands of miles/kilometers long. Exterior this zone a total eclipse appears equally a partial eclipse; the non-total parts of a full eclipse and partial eclipses are oft visible from over half the surface of the earth (assuming there are no clouds). Totality can last as long as seven and one half minutes, but is usually shorter (and the duration varies depending on your exact location). Observing solar eclipses is more unsafe than observing other solar phenomena. Information technology is safe to look at the sun during totality, simply y'all must either expect away or put on heart protection the moment totality ends. You usually have a strong reflex reaction which prevents you from looking at the sun for whatever period of fourth dimension, however this reflex does non operate during an eclipse, this is the reason people endure blindness during an eclipse.

Transits of Venus occur either once or twice every 121 and a one-half years. If there are two transits in this flow of time, those two transits are viii years autonomously. That is the instance during the 21st century: the last 1 was on June 8, 2004 and the next i willl be on June 6, 2012. If y'all have proper center protection, you lot tin can see the disk of Venus without magnification. A Venus transit can last equally long equally seven.9 hours. Such a transit will exist partially visible from well over half of the planet earth, but the consummate transit is visible from only nigh i third of the globe. However most Venus transits do non concluding that long and are visible over a smaller surface area (the duration of the transit varies depending on the location yous observe from). For more than information see http://www.transitofvenus.org/.

Transits of Mercury are more common than transits of Venus: Mercury transits occur on boilerplate every eight years (though the pattern is non regular). However Mercury's deejay during a transit is as well small to be seen with the unaided centre (you must use a telescope with a proper solar filter).

A number of phenomena are created by lite from the sun interacting with the atmosphere. These phenomena include rainbows, haloes, solar pillars, crepuscular rays, coronas, sundogs, glories and the light-green flash. Observing the green flash is safe as long as you look at lord's day only while information technology is cherry-red; observing rainbows is always safe; observing halos, solar pillars, crepuscular rays, coronas and sun glories is safe as long equally you make a reasonable effort to avoid looking straight at the sunday. Never point binoculars or a telescope direct at the sun even during sunrise or sunset.

For more information:

• The article "3 Rise Suns," past Christopher Sarnecki, February, 1999 contains more data on daytime solar phenomena.
• NASA: Solar Eclipse Dwelling Page.

The Moon

The first thing you will notice about the moon is that it changes phase over the course of its 29 1/2-mean solar day cycle. The phases are listed beneath (this shows the number of days into the cycle and the menstruum of time during which the moon is visible. These times are gauge and do not take into account daylight savings time or variations due to longitude).

1 day	New Moon	non visible
4 days	Waxing Crescent	8 AM to 10 PM
seven days	First Quarter	11 AM to 1 AM
10 days	Waxing Gibbous	2 PM to four AM
xiv days	Full Moon	v PM to 7 AM
18 days	Waning Gibbous	8 PM to 10 AM
22 days	Last Quarter	11 PM to 1 PM
26 days	Waning Crescent	ii AM to 4 PM

You will note the moon is visible during daytime hours a pregnant fraction of the time.

The crescent moon points to the position of the sun (except during the new moon, when the moon is not visible, and during the full moon, when there is no crescent). The moon frequently appears to signal slightly above or beneath the lord's day, but this is an optical illusion - it really does point to the lord's day.

You may have heard that the same function of the moon ever points to the world and half the moon tin can never exist seen. This is but partly true; due to a phenomenon called libration yous can run across 59 of the moon provided yous notice over a period of time. The moon wobbles very slowly when information technology orbits the earth, and this wobble is noticeable if y'all compare the border of the moon 24-hour interval after day for a month or and then.

With even a causal look at the moon, yous tin see maria (which are lowlands and dark colored), terrae (which are highlands and light colored) and the terminator (the line between the night part and the lit role of the moon). Features that are harder to see include craters and mount ranges. Despite what you might retrieve, the full moon is not the best time to look for lunar features; maria and terrae are easiest to meet during the total moon, just craters and other features are easier to run across when the sun is low in the lunar sky as seen by that feature. In other words it is best to notice the moon at several different phases (particularly starting time quarter and concluding quarter). Lunar craters are too small to exist seen without optical aid, however at that place is one mountain range that can be seen with the naked eye. If you await but subsequently kickoff quarter, the mountain range Apennines can be seen every bit irregular section of the terminator (which is normally a shine arc).

Lunar eclipses occur when the Earth passes between the Sun and the Moon. In a given yr in that location may be equally few as 2 lunar eclipses or equally many as five; some of these are partial eclipses and some are total. An eclipse is divided into iii stages, a "penumbral" phase when the moon is simply slightly darkened, an "umbral" phase when the moon is very dark and another "penumbral" stage when the moon is once again just slightly darkened. In some partial eclipses at that place is no umbral stage, and the entire eclipse is penumbral. In these situations, the eclipse is easy to miss. A Lunar Eclipse tin can concluding as long equally one and three quarters hour, but are unremarkably shorter.

On occasion the moon passes in forepart of a planet or a star, such an event is called an occultation. Occultations tin can exist predicted in advance and are like shooting fish in a barrel to observe if you programme alee. Note, the timing of an occultation depends on your exact location. A given occultation is visible from some locations on the world and non from others.

For more information:

• See Peter Alway'due south Lunar Eclipse Page for more data most lunar eclipses.
• The International Occultation Timing Clan gives data near lunar occultations.

Asteroids

Asteroids are small bodies, most of which are in orbits between Mars and Jupiter. All are faint.

The best time to detect an asteroid is when it is at opposition (that is the time it is closest to the globe). If it is visible at all, an asteroid will be visible simply as a dot of light that is difficult to distinguish from nearby stars. Of the hundreds of known asteroids, Vesta is the easiest to find and volition sometimes exist visible to the naked center. Experienced observers at very nighttime sites may be able to see asteroids in improver to Vesta.

For more information see the IAU: Minor Planet Eye. This site describes many asteroids that are not naked eye visible, pay attending to the magnitudes listed on this site.

Comets

Some comets are short-period comets, that is they return later a gear up flow, which tin can be equally brusk as three years or equally long equally 200 years (whatever comet with a flow longer than 200 years is not considered to be short-period). The all-time known of these comets is Comet Halley, which returns every 76 years. Many curt-period comets are known, merely non all comets are short-catamenia. New comets are continually existence discovered. Nearly newly discovered comets are not short-period; they volition non return for hundreds or thousands of years.

Comets generally spend near of their time far away from the lord's day. They are shut to the dominicus for a relatively short time, but this is the only time they are easy to observe. New comets are often detected far from the sun (when they are quite dim). Usually such comets are getting closer to the sunday, if so they can be expected to get brighter over time. Astronomers often make predictions virtually how much brighter these comets volition get, but such predictions are frequently wrong (Comet Kohoutek in 1973 was much dimmer than predicted, Comet West in 1975 was much brighter than predicted).

At whatsoever point in time, over a dozen comets can be seen through telescopes; however most are not naked eye visible. Comets that have bright easily visible tails occur roughly once every 10 years, comets that are naked eye visible with small fuzzy tails are somewhat more mutual. Comets accept at least two tails, a grit tail and an ion tail; the dust tail is the easiest to see, the ion tail is visible only in some very bright comets. When information technology is visible, the ion tail is oriented at a slight angle to the dust tail and is bluish in color.

For a listing of comets that are currently visible, see IAU: Astronomical Headlines. Note, nigh of the comets listed on this page are too dim to be seen without optical aid; pay attending to the magnitudes of the listed comets.

Interplanetary Dust

Dust within the solar system tin can reflect lite from the lord's day, and this reflected light can be seen from a dark site. Zodiacal light is a soft glow that is ordinarily triangular in shape. There are ii areas of zodiacal light, one in the east and one in the w; they are easier to see in winter. The zodiacal band is a band of lite that joins the 2 areas of zodiacal low-cal, but it is very difficult to see. An oval shaped section of the zodiacal band, the Gegenshein ofttimes is bright enough to be seen fifty-fifty when the zodiacal ring itself cannot be seen.

Aurorae

Aurorae are brilliant lights visible at night acquired by electrons entering the earth'due south upper atmosphere. Aurorae in the Northern Hemisphere are called Aurorae Borealis or Northern Lights; aurorae in the Southern Hemisphere are chosen Aurorae Australis or Southern Lights.

Aurorae are more frequent within an oval about 2,500 kilometers wide centered on the N Magnetic Pole (located in Northern Canada) and within an oval about 2,500 kilometers wide centered on the S Magnetic Pole (located in the sea virtually Antarctica). This means the Aurorae Borealis is most commonly seen from Alaska, Canada, Greenland and Iceland. It can exist seen, just less frequently from the northern continental United states, Scandinavia, Ireland and the United Kingdom. On rare occasions, aurora take been seen even further from the n magnetic pole. The Aurorae Australis is rarely seen since at that place are no populated areas most the S Magnetic Pole.

Aurora are more mutual at solar maximum (which occurs every 11 years). Aurora can be relatively common upwards to three years later the solar maximum. Scientists take been somewhat successful (simply not perfect) at predicting when aurorae will occur.

Aurorae can appear in several different shapes, but the about common shapes have been described as sheets, defunction and streamers. They can appear in different colors (green is the most mutual, however red, violet and bluish have been observed). Nether unusual conditions, aurora can appear to pulse on and off over a large department of the sky (the author has observed this only once). Aurorae observing does not crave dark skies, only colors and pulsation are subtle phenomena which are easier to observe if you are nighttime adapted and observing from a nighttime site.

For more information, see

• SpaceWeather.com: Science News and Data about the Sunday-World Environment.

Meteors

On any clear night you tin expect to see a number of meteors (meteors are sometimes incorrectly chosen "shooting stars"). The number you will come across is affected by several factors.

• The limiting magnitude. If the limiting magnitude is reduced by 1, this will reduce the number of meteors visible by a factor between ii and 3; if the limiting magnitude is reduced by ii, this volition reduce the number of meteors past a factor between 4 and 9.
• Time of day; meteors go through a diurnal cycle with a minimum at 6 PM and increasing to a maximum at 6 AM (of class you can't encounter meteors in daylight, but this cycle is one cistron in the number of meteors you will run into when it is dark).
• Time of year; there is an annual cycle of meteors - there are tend to be fewer meteors in March than there are in September.
• Falling star showers - On certain days in the year, the background rate of meteors increases, sometimes dramatically. For example between August 10-16, the Perseid falling star shower produces an elevated number of meteors.
• Each meteor shower has a "radiant." Meteors from the shower appear to "radiate" from this point. During a meteor shower, the number of meteors seen is highest if the radiant is high, preferably near the overhead point.
• A few shooting star showers, such as the Leonids, are only active for a menses of a few hours each twelvemonth. In such cases, observers in some parts of the world might see a lot of activeness, simply observers in other parts of the earth will not.

The main shooting star showers are shown below (the dates given below may vary slightly from twelvemonth to year).

• Quadrantid (peaks on January 3). Most action occurs during a xix hour period.
• Perseid (peaks on August 11). The nigh dependable of the major showers. Perseid meteors tin can be seen over a iii calendar week flow.
• Leonid (peaks on November 17). At their best, the Leonids are 100 times as intense as whatsoever other shower, but this only happens some years, in other years they are very weak. While some aspects of Leonid activity are known (it tends to follow a 33 twelvemonth cycle; typically there are a few years of strong storms followed by about 30 years of weak showers), attempts to predict the verbal time of maximum Leonid activity have been incorrect in the past. All the same, Leonid predictions seem to be more authentic now (predictions in the past few years have closely matched observations). Most activity occurs during a v hr period.
• Geminid (peaks on December 14). Geminid meteors can exist seen December seven through December 15.

If yous programme to observe meteors, your best bet is to wait for a major shower, such as the Perseids. You tin try to discover any night of the yr, but you may observe for a long time and not see anything. It is all-time to bring a chair, anything else you need to be comfortable (perhaps warm clothing), sit back, relax, and watch. Typical non-shower observation rates at midnight at a nighttime sight during March are nix to 3 per hour; typical ascertainment rates during September (midnight at a dark sight) are eight to 10 per hour.

With a unproblematic radio (in the United States use an FM radio) information technology is possible to find the presence of meteors. This tin can be washed during the daytime or night, when it is articulate or when it is cloudy. You lot may want to consider trying this if it is overcast during a falling star shower.

For more data

• The International Meteor Organization.

Artificial Satellites

There are thousands of man-made satellites in orbit around the world. Some are also dim to be seen with the unaided eye. Even so others can easily be seen if you know when and where to look. In a given evening, yous can await to see several satellites; they appear as dots of light that slowly move across the heaven.

For more than data see "What Satellite is That?" by Christopher Sarnecki, June, 1999.

Galaxies

The universe is composed of billions of galaxies. If y'all go outside at dark, almost all the objects yous tin encounter with the unaided eye are inside our own Milky Way galaxy. In that location are four exceptions:

• M31, The Andromeda Galaxy - Easy to see from a relatively dark site.
• The Large Magellanic Cloud - Easy to see, but only from the Southern Hemisphere.
• The Small Magellanic Deject - Easy to see, but merely from the Southern Hemisphere.
• M33, The Triangulum Galaxy - Few naked eye observations have been reported, almost from experienced observers at very dark sites. M33 is very hard to see without optical assist.

Our Galaxy, the Milky way, can be seen from whatever reasonably dark site as a band of light that extends across the sky.

Stars

In general all stars vary slightly in brightness over time. Most of these changes are insignificant, yet some stars vary noticeably in brightness. The majority of these so-chosen variable stars change in brightness over a period somewhere between a few hours and a twelvemonth. A few such stars can be seen with the naked eye; if one is conscientious, persistent and patient, information technology is possible to track the variations of these stars. In some cases the star is visible during part of its range and not visible during the residue of its range.

Two types of variable stars, novae and supernovae, change brightness dramatically and unpredictably. Novae volition increment in effulgence from 7 to 16 magnitudes over a solar day or two then subtract in brightness slowly over the next several months. Novae vivid plenty to exist seen with the naked centre occur once every few years. Supernovae increase in brightness over 20 magnitudes in the bridge of a few days and then decline slowly over the next few years. Bright supernovae are rare. Over the past 400 years, at that place have been only three naked eye supernovae, one in the year 1604, one in 1885 and one in 1987. Both novae and supernovae are unpredictable. Information technology is possible to locate a previously undiscovered novae or supernovae with persistence and luck.

The color of stars is easily observed. Color is direct related to the star's temperature. The coldest stars are cherry; the hottest stars are blueish-white. Stars with intermediate temperatures can exist orange, yellow or white. It is piece of cake to tell the colour of brilliant stars, but hard to tell the color of the dimmer stars (dim stars often appear white fifty-fifty though they may exist red or blueish or some other color).

Many of the points of low-cal that announced to be stars are in fact double stars or even triple or quadruple stars. In a few cases, it is possible to "dissever" these stars (that is detect the different components) with the naked center.

In some cases, stars tin exist institute in large groups called "clusters." There are 2 types of clusters, globular and open. There are a few globular clusters and a few open clusters visible with the naked center (they include Omega Centauri, M13 and the Pleiades).

In addition, stars can be grouped into either associations or streams these are stars that are loosely bound merely are gradually moving away from each other. Many associations and streams are visible, however it is not ever easy to tell which stars are included and which are not. Ii of the near obvious associations involve some of the brightest stars in Ursa Major and Orion.

For more data:

• The American Association of Variable Star Observers posts information about variable stars and lists of newly discovered novae. Stars listed with magnitudes greater than six.5 will be difficult to come across with the naked eye.
• A listing of naked heart clusters can be found at The National Deep Sky Observers Order (Observing the Deep Sky with the Naked Eye).
• For a list of naked eye double stars, see "Observing Naked (or I got five.5 arcmins resolution)," by Christopher Sarnecki, October, 1999 (in part) and Jan 2000 (in part) and "Apprentice Astronomer Makes Tape Double Star Divide," by Christopher Sarnecki, August, 2000.

Nebulae

Nebulae are areas of gas within the galaxy. Some nebulae (emission, reflection and planetary nebulae) either glow or reflect light from nearby stars; many such nebulae can be seen from the earth. Other nebulae (nighttime nebulae) practice non glow, but can be detected because stars cannot be seen through them (these nebulae are opaque and starlight cannot pass through them). A few nebulae are visible to the unaided eye, they include:

• The Orion Nebula.
• The Pipage Nebula.
• The Nighttime Lanes in the Milky Mode.
• The Coal Sack (only visible from Southern Hemisphere).

For more information see The National Deep Sky Observers Society (Observing the Deep Sky with the Naked Eye).

Dark Myopia

Many people suffer from nearly-sightedness or myopia, and they correct for it with eyeglasses or contact lenses. It has been known for some time that myopia often gets worse when observing at nighttime. This is called night myopia. It'south not a serious condition, and most people don't realize they have it. It's temporary and goes away during the daytime. All the same if you endure from this condition, your night visible isn't quite as expert as it could be and y'all may not be able to come across some of the objects described earlier in this commodity.

If you lot use a telescope or binoculars, the focus knob volition allow yous to compensate for dark myopia. However this doesn't work for naked eye observing.

The first step is to determine if this situation applies to you (each person'due south eyes are dissimilar). There is a visitor that sells a "night myopia flipper" set. These are lens that you can place over your eyeglasses (or contact lens) and decide if boosted correction is necessary to deal with nighttime myopia. Take the flipper gear up and wait until your optics are dark adapted. And so use trail and error to find out which correction (if any) works best. Warning, if you are not conscientious you may terminate up with an improper correction and this can lead to headaches. Take your time, may certain yous allow your optics to adjust.

To order a ready, go to http://world wide web.optego.com/. (Expect for the "Night Myopia Diagnostic Flippers.")

If you recollect correction is advisable, you should talk over the situation with your eye intendance professional. Think this may require the purchase of eyeglasses that will only exist useful for naked center nighttime observing; such eyeglasses are not necessary for binocular or telescope viewing. Whether such a purchase is worth the expense needs to be an private decision.

For more information at that place is an article in Heaven and Telescope magazine. Run into Joshua Roth. September 2005. "Special Report: Dark Myopia." Sky and Telescope. Vol 110, Number three.

Photography

For data on taking photographs of astronomical objects, see "Elementary Astrophotography" by Clayton Kessler.

Binoculars and Telescopes

Afterward gaining experience with observing with the naked eye, the side by side step is to attempt observing the same objects with binoculars. Many objects that are barely visible with the naked centre reveal a lot of detail when observed through binoculars. In addition, binoculars increment the number of objects you lot can see.

Later on gaining experience with binoculars, you may feel set to purchase a telescope. Keep in mind that many people who purchase a telescope on impulse, are subsequently unhappy with their musical instrument. To avoid this, take your time when deciding to purchase a telescope. For more information, encounter Telescope Links.

References

For a listing of the reference materials used to produce this guide, see the University Lowbrow Astronomer'southward Book List.

Links

• Academy Lowbrow Astronomers Observer's Guide.
• The Home Page for the Academy Lowbrow Astronomers.
• The University of Michigan Astronomy Department.
• The University of Michigan Gateway.
• A List of Other Astronomy Clubs in SE Michigan.
• Other Astronomy Related Pages.

Copyright Info

Copyright © 2015, the University Lowbrow Astronomers. (The University Lowbrow Astronomers are an amateur astronomy club based in Ann Arbor, Michigan).

This page originally appeared in Reflections of the University Lowbrow Astronomers (the club newsletter).

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This folio revised Monday, June 22, 2022 11:12 AM .

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