Apparent magnitude

File:65Cyb-LB3-apmag.jpg

Asteroid 65 Cybele and two stars in the constellation Aquarius, with their magnitudes labeled

Apparent magnitude (Template:Mvar) is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.

Unless stated otherwise, the word magnitude in astronomy usually refers to a celestial object's apparent magnitude. The magnitude scale likely dates to before the ancient Roman astronomer Claudius Ptolemy, whose star catalog popularized the system by listing stars from 1st magnitude (brightest) to 6th magnitude (dimmest).<ref>Template:Cite book</ref> The modern scale was mathematically defined to closely match this historical system by Norman Pogson in 1856.

The scale is reverse logarithmic: the brighter an object is, the lower its magnitude number. A difference of 1.0 in magnitude corresponds to the brightness ratio of <math>\sqrt[5]{100}</math>, or about 2.512. For example, a magnitude 2.0 star is 2.512 times as bright as a magnitude 3.0 star, 6.31 times as magnitude 4.0, and 100 times magnitude 7.0.

The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46. The faintest stars visible with the naked eye on the darkest night have apparent magnitudes of about +6.5, though this varies depending on a person's eyesight and with altitude and atmospheric conditions.<ref>Template:Cite journal</ref> The apparent magnitudes of known objects range from the Sun at −26.832 to objects in deep Hubble Space Telescope images of magnitude +31.5.<ref name="AAVSO">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The measurement of apparent magnitude is called photometry. Photometric measurements are made in the ultraviolet, visible, or infrared wavelength bands using standard passband filters belonging to photometric systems such as the UBV system or the Strömgren uvbyβ system. Measurement in the V-band may be referred to as the apparent visual magnitude.

Absolute magnitude is a related quantity which measures the luminosity that a celestial object emits, rather than its apparent brightness when observed, and is expressed on the same reverse logarithmic scale. Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of Template:Convert. Therefore, it is of greater use in stellar astrophysics since it refers to a property of a star regardless of how close it is to Earth. But in observational astronomy and popular stargazing, references to "magnitude" are understood to mean apparent magnitude.

Amateur astronomers commonly express the darkness of the sky in terms of limiting magnitude, i.e. the apparent magnitude of the faintest star they can see with the naked eye. This can be useful as a way of monitoring the spread of light pollution.

Apparent magnitude is technically a measure of illuminance, which can also be measured in photometric units such as lux.<ref>Template:Cite journal</ref>

History

Visible to typical human eye<ref name="SIMBAD-mag6.5"/>	Apparent magnitude	Bright- ness relative to Vega	Number of stars (other than the Sun) brighter than apparent magnitude<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> in the night sky
Yes	−1.0	251%	1 (Sirius)
	Template:00.0	100%	5 (Vega, Canopus, Alpha Centauri, Arcturus)
	Template:01.0	40%	15
	Template:02.0	16%	48
	Template:03.0	6.3%	171
	Template:04.0	2.5%	513
	Template:05.0	1.0%	Template:Val
	Template:06.0	0.4%	Template:Val
	Template:06.5	0.25%	Template:Val<ref>Bright Star Catalogue</ref>
No	Template:07.0	0.16%	Template:Val
	Template:08.0	0.063%	Template:Val
	Template:09.0	0.025%	Template:Val
	10.0	0.010%	Template:Val

The scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars in the night sky were said to be of first magnitude (Template:Mvar = 1), whereas the faintest were of sixth magnitude (Template:Mvar = 6), which is the limit of human visual perception (without the aid of a telescope). Each grade of magnitude was considered twice the brightness of the following grade (a logarithmic scale), although that ratio was subjective as no photodetectors existed. This rather crude scale for the brightness of stars was popularized by Ptolemy in his Almagest and is generally believed to have originated with Hipparchus. This cannot be proved or disproved because Hipparchus's original star catalogue is lost. The only preserved text by Hipparchus himself (a commentary to Aratus) clearly documents that he did not have a system to describe brightness with numbers: He always uses terms like "big" or "small", "bright" or "faint" or even descriptions such as "visible at full moon".<ref>Hoffmann, S., Hipparchs Himmelsglobus, Springer, Wiesbaden/ New York, 2017</ref>

In 1856, Norman Robert Pogson formalized the system by defining a first magnitude star as a star that is 100 times as bright as a sixth-magnitude star, thereby establishing the logarithmic scale still in use today. This implies that a star of magnitude Template:Mvar is about 2.512 times as bright as a star of magnitude Template:Math. This figure, the fifth root of 100, became known as Template:Vanchor.<ref>Template:Cite journal</ref> The 1884 Harvard Photometry and 1886 Potsdamer Durchmusterung star catalogs popularized Pogson's ratio, and eventually it became a de facto standard in modern astronomy to describe differences in brightness.<ref>Template:Cite book</ref>

Defining and calibrating what magnitude 0.0 means is difficult, and different types of measurements which detect different kinds of light (possibly by using filters) have different zero points. Pogson's original 1856 paper defined magnitude 6.0 to be the faintest star the unaided eye can see,<ref>Template:Cite journal</ref> but the true limit for faintest possible visible star varies depending on the atmosphere and how high a star is in the sky. The Harvard Photometry used an average of 100 stars close to Polaris to define magnitude 5.0.<ref>Template:Cite book</ref> Later, the Johnson UVB photometric system defined multiple types of photometric measurements with different filters, where magnitude 0.0 for each filter is defined to be the average of six stars with the same spectral type as Vega. This was done so the color index of these stars would be 0.<ref>Template:Cite journal</ref> Although this system is often called "Vega normalized", Vega is slightly dimmer than the six-star average used to define magnitude 0.0, meaning Vega's magnitude is normalized to 0.03 by definition.

Limiting Magnitudes for Visual Observation at High Magnification<ref>Template:Cite book</ref>

Telescope aperture (mm)	Limiting Magnitude
35	11.3
60	12.3
102	13.3
152	14.1
203	14.7
305	15.4
406	15.7
508	16.4

With the modern magnitude systems, brightness is described using Pogson's ratio. In practice, magnitude numbers rarely go above 30 before stars become too faint to detect. While Vega is close to magnitude 0, there are four brighter stars in the night sky at visible wavelengths (and more at infrared wavelengths) as well as the bright planets Venus, Mars, and Jupiter, and since brighter means smaller magnitude, these must be described by negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has a magnitude of −1.4 in the visible. Negative magnitudes for other very bright astronomical objects can be found in the table below.

Astronomers have developed other photometric zero point systems as alternatives to Vega normalized systems. The most widely used is the AB magnitude system,<ref>Template:Cite journal</ref> in which photometric zero points are based on a hypothetical reference spectrum having constant flux per unit frequency interval, rather than using a stellar spectrum or blackbody curve as the reference. The AB magnitude zero point is defined such that an object's AB and Vega-based magnitudes will be approximately equal in the V filter band. However, the AB magnitude system is defined assuming an idealized detector measuring only one wavelength of light, while real detectors accept energy from a range of wavelengths.

Measurement

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Precision measurement of magnitude (photometry) requires calibration of the photographic or (usually) electronic detection apparatus. This generally involves contemporaneous observation, under identical conditions, of standard stars whose magnitude using that spectral filter is accurately known. Moreover, as the amount of light actually received by a telescope is reduced due to transmission through the Earth's atmosphere, the airmasses of the target and calibration stars must be taken into account. Typically one would observe a few different stars of known magnitude which are sufficiently similar. Calibrator stars close in the sky to the target are favoured (to avoid large differences in the atmospheric paths). If those stars have somewhat different zenith angles (altitudes) then a correction factor as a function of airmass can be derived and applied to the airmass at the target's position. Such calibration obtains the brightness as would be observed from above the atmosphere, where apparent magnitude is defined.Template:Cn

The apparent magnitude scale in astronomy reflects the received power of stars and not their amplitude. Newcomers should consider using the relative brightness measure in astrophotography to adjust exposure times between stars. Apparent magnitude also integrates over the entire object, regardless of its focus, and this needs to be taken into account when scaling exposure times for objects with significant apparent size, like the Sun, Moon and planets. For example, directly scaling the exposure time from the Moon to the Sun works because they are approximately the same size in the sky. However, scaling the exposure from the Moon to Saturn would result in an overexposure if the image of Saturn takes up a smaller area on your sensor than the Moon did (at the same magnification, or more generally, f/#).

Calculations

File:VISTA Magellanic Cloud Survey view of the Tarantula Nebula.jpg

Image of 30 Doradus taken by ESO's VISTA. This nebula has a visual magnitude of 8.

File:Apparent magnitude.svg

Graph of relative brightness versus magnitude

The dimmer an object appears, the higher the numerical value given to its magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of exactly 100. Therefore, the magnitude Template:Mvar, in the spectral band Template:Mvar, would be given by <math display="block">m_{x}= -5 \log_{100} \left(\frac {F_x}{F_{x,0}}\right),</math> which is more commonly expressed in terms of common (base-10) logarithms as <math display="block">m_{x} = -2.5 \log_{10} \left(\frac {F_x}{F_{x,0}}\right),</math> where Template:Mvar is the observed irradiance using spectral filter Template:Mvar, and Template:Math is the reference flux (zero-point) for that photometric filter. Since an increase of 5 magnitudes corresponds to a decrease in brightness by a factor of exactly 100, each magnitude increase implies a decrease in brightness by the factor <math>\sqrt[5]{100} \approx 2.512</math> (Pogson's ratio). Inverting the above formula, a magnitude difference Template:Math implies a brightness factor of <math display="block"> \frac{F_2}{F_1} = 100^\frac{\Delta m}{5} = 10^{0.4 \Delta m} \approx 2.512^{\Delta m}.</math>

Example: Sun and Moon

What is the ratio in brightness between the Sun and the full Moon?

The apparent magnitude of the Sun is −26.832<ref name="IAU2015B2"/> (brighter), and the mean magnitude of the full moon is −12.74<ref name="moon-fact" /> (dimmer).

Difference in magnitude: <math display="block"> x = m_1 - m_2 = (-12.74) - (-26.832) = 14.09. </math>

Brightness factor: <math display="block"> v_b = 10^{0.4 x} = 10^{0.4 \times 14.09} \approx 432\,513. </math>

The Sun appears to be approximately Template:Val times as bright as the full Moon.

Magnitude addition

Sometimes one might wish to add brightness. For example, photometry on closely separated double stars may only be able to produce a measurement of their combined light output. To find the combined magnitude of that double star knowing only the magnitudes of the individual components, this can be done by adding the brightness (in linear units) corresponding to each magnitude.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <math display="block"> 10^{-m_f \times 0.4} = 10^{-m_1 \times 0.4} + 10^{-m_2 \times 0.4}. </math>

Solving for <math>m_f</math> yields <math display="block"> m_f = -2.5\log_{10} \left(10^{-m_1 \times 0.4} + 10^{-m_2 \times 0.4} \right), </math> where Template:Mvar is the resulting magnitude after adding the brightnesses referred to by Template:Math and Template:Math.

Apparent bolometric magnitude

While magnitude generally refers to a measurement in a particular filter band corresponding to some range of wavelengths, the apparent or absolute bolometric magnitude (m_bol) is a measure of an object's apparent or absolute brightness integrated over all wavelengths of the electromagnetic spectrum (also known as the object's irradiance or power, respectively). The zero point of the apparent bolometric magnitude scale is based on the definition that an apparent bolometric magnitude of 0 mag is equivalent to a received irradiance of 2.518×10⁻⁸ watts per square metre (W·m⁻²).<ref name="IAU2015B2">Template:Cite journal</ref>

Absolute magnitude

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} While apparent magnitude is a measure of the brightness of an object as seen by a particular observer, absolute magnitude is a measure of the intrinsic brightness of an object. Flux decreases with distance according to an inverse-square law, so the apparent magnitude of a star depends on both its absolute brightness and its distance (and any extinction). For example, a star at one distance will have the same apparent magnitude as a star four times as bright at twice that distance. In contrast, the intrinsic brightness of an astronomical object, does not depend on the distance of the observer or any extinction.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The absolute magnitude Template:Mvar, of a star or astronomical object is defined as the apparent magnitude it would have as seen from a distance of Template:Convert. The absolute magnitude of the Sun is 4.83 in the V band (visual), 4.68 in the Gaia satellite's G band (green) and 5.48 in the B band (blue).<ref name="Bband">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Gband">Template:Cite journal</ref><ref name="Bessell2005">Template:Cite journal</ref>

In the case of a planet or asteroid, the absolute magnitude Template:Mvar rather means the apparent magnitude it would have if it were Template:Convert from both the observer and the Sun, and fully illuminated at maximum opposition (a configuration that is only theoretically achievable, with the observer situated on the surface of the Sun).<ref name="Luciuk">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Standard reference values

citation

CitationClass=web }}</ref>
Band	Template:Mvar (μm)	Template:Math (FWHM)	Flux at Template:Math, Template:Math
			Jy	10−20 erg/(s·cm2·Hz)
U	0.36	0.15	1810	1.81
B	0.44	0.22	4260	4.26
V	0.55	0.16	3640	3.64
R	0.64	0.23	3080	3.08
I	0.79	0.19	2550	2.55
J	1.26	0.16	1600	1.60
H	1.60	0.23	1080	1.08
K	2.22	0.23	Template:0670	0.67
L	3.50
g	0.52	0.14	3730	3.73
r	0.67	0.14	4490	4.49
i	0.79	0.16	4760	4.76
z	0.91	0.13	4810	4.81

The magnitude scale is a reverse logarithmic scale. A common misconception is that the logarithmic nature of the scale is because the human eye itself has a logarithmic response. In Pogson's time this was thought to be true (see Weber–Fechner law), but it is now believed that the response is a power law Template:Xref.<ref>Template:Cite journal</ref>

Magnitude is complicated by the fact that light is not monochromatic. The sensitivity of a light detector varies according to the wavelength of the light, and the way it varies depends on the type of light detector. For this reason, it is necessary to specify how the magnitude is measured for the value to be meaningful. For this purpose the UBV system is widely used, in which the magnitude is measured in three different wavelength bands: U (centred at about 350 nm, in the near ultraviolet), B (about 435 nm, in the blue region) and V (about 555 nm, in the middle of the human visual range in daylight). The V band was chosen for spectral purposes and gives magnitudes closely corresponding to those seen by the human eye. When an apparent magnitude is discussed without further qualification, the V magnitude is generally understood.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Because cooler stars, such as red giants and red dwarfs, emit little energy in the blue and UV regions of the spectrum, their power is often under-represented by the UBV scale. Indeed, some L and T class stars have an estimated magnitude of well over 100, because they emit extremely little visible light, but are strongest in infrared.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Measures of magnitude need cautious treatment and it is extremely important to measure like with like. On early 20th century and older orthochromatic (blue-sensitive) photographic film, the relative brightnesses of the blue supergiant Rigel and the red supergiant Betelgeuse irregular variable star (at maximum) are reversed compared to what human eyes perceive, because this archaic film is more sensitive to blue light than it is to red light. Magnitudes obtained from this method are known as photographic magnitudes, and are now considered obsolete.<ref>Template:Cite journal</ref>

For objects within the Milky Way with a given absolute magnitude, 5 is added to the apparent magnitude for every tenfold increase in the distance to the object. For objects at very great distances (far beyond the Milky Way), this relationship must be adjusted for redshifts and for non-Euclidean distance measures due to general relativity.<ref name=umeh>Template:Cite journal</ref><ref name=hogg>Template:Cite arXiv</ref>

For planets and other Solar System bodies, the apparent magnitude is derived from its phase curve and the distances to the Sun and observer.<ref>Template:Cite journal</ref>

List of apparent magnitudes

Some of the listed magnitudes are approximate. Telescope sensitivity depends on observing time, optical bandpass, and interfering light from scattering and airglow.

Apparent visual magnitudes of celestial objects

Apparent magnitude (V)	Object	Seen from...	Notes
−67.57	gamma-ray burst GRB 080319B	seen from 1 AU away	would be over Template:Val (20 quadrillion) times as bright as the Sun when seen from the Earth
−43.27	star NGC 2403 V14	seen from 1 AU away
−41.82	star NGC 2363-V1	seen from 1 AU away
−41.39	star Cygnus OB2-12	seen from 1 AU away
−40.67	star M33-013406.63	seen from 1 AU away
−40.17	star η Carinae A	seen from 1 AU away
−40.07	star Zeta1 Scorpii	seen from 1 AU away
−39.66	star R136a1	seen from 1 AU away
−39.47	star P Cygni	seen from 1 AU away
−38.00	star Rigel	seen from 1 AU away	would be seen as a large, very bright bluish disk of 35° apparent diameter
−37.42	star Betelgeuse	seen from 1 AU away
−30.30	star Sirius A	seen from 1 AU away
−29.30	star Sun	seen from Mercury at perihelion
−27.40	star Sun	seen from Venus at perihelion
−26.83	star Sun	seen from Earth<ref name="IAU2015B2"/>	about 400,000 times as bright as mean full Moon
−25.60	star Sun	seen from Mars at aphelion
−25	Minimum brightness that causes the typical eye slight pain to look at
−23.00	star Sun	seen from Jupiter at aphelion
−21.70	star Sun	seen from Saturn at aphelion
−21.00	star Sun	seen from Earth on an overcast midday	measuring about 1000 lux
−20.20	star Sun	seen from Uranus at aphelion
−19.30	star Sun	seen from Neptune
−19.00	star Sun	seen from Earth on a very strongly overcast midday	measuring about 100 lux
−18.20	star Sun	seen from Pluto at aphelion
−17.70	planet Earth	seen fully illuminated as earthlight from the Moon<ref name="Agrawal">Template:Cite journal</ref>
−16.70	star Sun	seen from Eris at aphelion
−16.00	star Sun	as twilight on Earth	citation	CitationClass=web }}</ref>
−14.2	An illumination level of 1 lux<ref>Template:Cite book</ref><ref name =IM08>Template:Cite book</ref>
−12.60	full moon	seen from Earth at perihelion	maximum brightness of perigee + perihelion + full Moon (~0.267 lux; mean distance value is −12.74,<ref name="moon-fact" /> though values are about 0.18 magnitude brighter when including the opposition effect)
−12.40	Betelgeuse (when supernova)	seen from Earth when it goes supernova<ref>Template:Cite journal</ref>
−11.20	star Sun	seen from Sedna at aphelion
−10.00	Comet Ikeya–Seki (1965)	seen from Earth	which was the brightest Kreutz Sungrazer of modern times<ref name="brightest">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
−9.50	Iridium (satellite) flare	seen from Earth	maximum brightness
−9 to −10	Phobos (moon)	seen from Mars	maximum brightness
−7.50	supernova of 1006	seen from Earth	the brightest stellar event in recorded history (7200 light-years away)<ref name="SN1006" />
−6.80	Alpha Centauri A	seen from Proxima Centauri b	citation	CitationClass=web }}</ref>
−6.00	The total integrated magnitude of the night sky (incl. airglow)	seen from Earth	measuring about 0.002 lux
−6.00	Crab Supernova of 1054	seen from Earth	(6500 light-years away)<ref name="SN1054" />
−5.90	International Space Station	seen from Earth	when the ISS is at its perigee and fully lit by the Sun<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
−4.92	planet Venus	seen from Earth	maximum brightness<ref name="Mallama_and_Hilton" /> when illuminated as a crescent
−4.14	planet Venus	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
−4	Faintest objects observable during the day with naked eye when Sun is high. An astronomical object casts human-visible shadows when its apparent magnitude is equal to or lower than −4 <ref>NASA Science Question of the Week. Gsfc.nasa.gov (7 April 2006). Retrieved on 26 April 2013.</ref>
−3.99	star Epsilon Canis Majoris	seen from Earth	maximum brightness of 4.7 million years ago, the historical brightest star of the last and next five million years.<ref name=tomkin>Template:Cite journal – based on computations from HIPPARCOS data. (The calculations exclude stars whose distance or proper motion is uncertain.) </ref>
−3.69	Moon	lit by earthlight, reflecting earthshine seen from Earth (maximum)<ref name="Agrawal"/>
−2.98	planet Venus	seen from Earth	minimum brightness during transits.
−2.94	planet Jupiter	seen from Earth	maximum brightness<ref name="Mallama_and_Hilton" />
−2.94	planet Mars	seen from Earth	maximum brightness<ref name="Mallama_and_Hilton" />
−2.5	Faintest objects visible during the day with naked eye when Sun is less than 10° above the horizon
−2.50	new moon	seen from Earth	minimum brightness
−2.50	planet Earth	seen from Mars	maximum brightness
−2.48	planet Mercury	seen from Earth	maximum brightness at superior conjunction (unlike Venus, Mercury is at its brightest when on the far side of the Sun, the reason being their different phase curves)<ref name="Mallama_and_Hilton" />
−2.20	planet Jupiter	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
−1.66	planet Jupiter	seen from Earth	minimum brightness<ref name="Mallama_and_Hilton" />
−1.47	star system Sirius	seen from Earth	Brightest star except for the Sun at visible wavelengths<ref name="SIMBAD-Sirius" />
−0.83	star Eta Carinae	seen from Earth	apparent brightness as a supernova impostor in April 1843
−0.72	star Canopus	seen from Earth	2nd brightest star in night sky<ref name="SIMBAD-Canopus" />
−0.55	planet Saturn	seen from Earth	maximum brightness near opposition and perihelion when the rings are angled toward Earth<ref name="Mallama_and_Hilton" />
−0.30	Halley's comet	seen from Earth	Expected apparent magnitude at 2061 passage
−0.27	star system Alpha Centauri AB	seen from Earth	Combined magnitude (3rd brightest star in night sky)
−0.04	star Arcturus	seen from Earth	4th brightest star to the naked eye<ref name="SIMBAD-Arcturus" />
−0.01	star Alpha Centauri A	seen from Earth	4th brightest individual star visible telescopically in the night sky
+0.03	star Vega	seen from Earth	originally chosen as a definition of the zero point<ref name="SIMBAD-Vega" />
+0.23	planet Mercury	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
+0.46	star Sun	seen from Alpha Centauri
+0.46	planet Saturn	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
+0.71	planet Mars	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
+0.90	Moon	seen from Mars	maximum brightness
+1.17	planet Saturn	seen from Earth	minimum brightness<ref name="Mallama_and_Hilton" />
+1.33	star Alpha Centauri B	seen from Earth
+1.86	planet Mars	seen from Earth	minimum brightness<ref name="Mallama_and_Hilton" />
+1.98	star Polaris	seen from Earth	mean brightness<ref>Template:Cite journal</ref>
+2.00	star system T CrB (when nova)	seen from Earth	Star system that goes nova every 80 years
+2.40	Halley's Comet	seen from Earth	About Magnitude during 1986 perihelion
+3	Faintest objects visible in an urban neighborhood with naked eye
+3.03	supernova SN 1987A	seen from Earth	in the Large Magellanic Cloud (160,000 light-years away)
+3.44	Andromeda Galaxy	seen from Earth	M31<ref name="SIMBAD-M31" />
+4	Faintest objects visible in a suburban neighborhood with naked eye
+4.00	Orion Nebula	seen from Earth	M42
+4.38	moon Ganymede	seen from Earth	maximum brightness<ref name="horizons-Ganymede" /> (moon of Jupiter and the largest moon in the Solar System)
+4.50	open cluster M41	seen from Earth	an open cluster that may have been seen by Aristotle<ref name="Aristotle">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
+4.50	Sagittarius Dwarf Spheroidal Galaxy	seen from Earth
+5.20	asteroid Vesta	seen from Earth	maximum brightness
citation	CitationClass=web }}</ref>	planet Uranus	seen from Earth	maximum brightness<ref name="Mallama_and_Hilton" /> (Uranus comes to perihelion in 2050)
+5.68	planet Uranus	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
+5.72	spiral galaxy M33	seen from Earth	which is used as a test for naked eye seeing under dark skies<ref name="SIMBAD-M33">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref><ref name="M33">{{#invoke:citation/CS1|citation	CitationClass=web }} (Shows bolometric magnitude not visual magnitude.)</ref>
+5.80	gamma-ray burst GRB 080319B	seen from Earth	Peak visual magnitude (the "Clarke Event") seen on Earth on 19 March 2008 from a distance of 7.5 billion light-years.
+6.03	planet Uranus	seen from Earth	minimum brightness<ref name="Mallama_and_Hilton" />
+6.49	asteroid Pallas	seen from Earth	maximum brightness
+6.5	Approximate limit of stars observed by a mean naked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5.<ref name="SIMBAD-mag6.5"/>
+6.50	global cluster M2	seen from Earth	mean naked-eye target
+6.64	dwarf planet Ceres	seen from Earth	maximum brightness
+6.75	asteroid Iris	seen from Earth	maximum brightness
+6.90	spiral galaxy M81	seen from Earth	citation	CitationClass=web }}</ref>
+7.25	planet Mercury	seen from Earth	minimum brightness<ref name="Mallama_and_Hilton" />
citation	CitationClass=web }}</ref>|| planet Neptune || seen from Earth	maximum brightness<ref name="Mallama_and_Hilton" /> (Neptune comes to perihelion in 2042)
+7.78	planet Neptune	seen from Earth	mean brightness<ref name="Mallama_and_Hilton" />
+8	Extreme naked-eye limit, Class 1 on Bortle scale, the darkest skies available on Earth.<ref name="Bortle">{{#invoke:citation/CS1|citation			CitationClass=web }}</ref>
+8.00	planet Neptune	seen from Earth	minimum brightness<ref name="Mallama_and_Hilton" />
+8.10	moon Titan	seen from Earth	maximum brightness; largest moon of Saturn;<ref name="horizons-Titan" /><ref name="arval" /> mean opposition magnitude 8.4<ref name="jpl-sat" />
+8.29	star UY Scuti	seen from Earth	Maximum brightness; one of largest known stars by radius
+8.94	asteroid 10 Hygiea	seen from Earth	maximum brightness<ref name="AstDys-Hygiea" />
+9.30	spiral galaxy M63	seen from Earth
+9.5	Faintest objects visible using common 10×50 binoculars under typical conditions<ref name="binoculars"/>
+10	Apollo 8 CSM in orbit around the Moon	seen from Earth	citation	CitationClass=web }}</ref>
+10	star system T CrB(average)	seen from Earth	Star system that goes nova every 80 years
+10.20	moon Iapetus	seen from Earth	maximum brightness,<ref name="arval" /> brightest when west of Saturn and takes 40 days to switch sides
+11.05	star Proxima Centauri	seen from Earth	closest star (other than the Sun)
+11.8	moon Phobos	seen from Earth	Maximum brightness; brighter moon of Mars
+12.23	star R136a1	seen from Earth	Most luminous and massive star known<ref>Template:Cite news</ref>
+12.89	moon Deimos	seen from Earth	Maximum brightness
+12.91	quasar 3C 273	seen from Earth	brightest (luminosity distance of 2.4 billion light-years)
+13.42	moon Triton	seen from Earth	Maximum brightness<ref name="jpl-sat" />
+13.65	dwarf planet Pluto	seen from Earth	maximum brightness,<ref name="pluto" /> 725 times fainter than magnitude 6.5 naked eye skies
+13.9	moon Titania	seen from Earth	Maximum brightness; brightest moon of Uranus
+14.1	star WR 102	seen from Earth	Hottest known star
+15.4	centaur Chiron	seen from Earth	maximum brightness<ref name="AstDys-Chiron" />
+15.55	moon Charon	seen from Earth	maximum brightness (the largest moon of Pluto)
+16.8	dwarf planet Makemake	seen from Earth	Current opposition brightness<ref name="AstDys-Makemake" />
+17.27	dwarf planet Haumea	seen from Earth	Current opposition brightness<ref name="AstDys-Haumea" />
+18.7	dwarf planet Eris	seen from Earth	Current opposition brightness
+19.5	Faintest objects observable with the Catalina Sky Survey 0.7-meter telescope using a 30-second exposure<ref>{{#invoke:citation/CS1|citation			CitationClass=web }}</ref> and also the approximate limiting magnitude of Asteroid Terrestrial-impact Last Alert System (ATLAS)
+20.7	moon Callirrhoe	seen from Earth	(small ≈8 km satellite of Jupiter)<ref name="jpl-sat" />
+22	Faintest objects observable in visible light with a 600 mm (24″) Ritchey-Chrétien telescope with 30 minutes of stacked images (6 subframes at 5 minutes each) using a CCD detector<ref name="24inch">{{#invoke:citation/CS1|citation			CitationClass=web }}</ref>
+22.8	Luhman 16	seen from Earth	Closest brown dwarfs (Luhman 16A=23.25, Luhman 16B=24.07)<ref name="Boffin et al. 2014" />
+22.91	moon Hydra	seen from Earth	maximum brightness of Pluto's moon
+23.38	moon Nix	seen from Earth	maximum brightness of Pluto's moon
+24	Faintest objects observable with the Pan-STARRS 1.8-meter telescope using a 60-second exposure<ref>{{#invoke:citation/CS1|citation			CitationClass=web }}</ref> This is currently the limiting magnitude of automated allsky astronomical surveys.
+25.0	moon Fenrir	seen from Earth	(small ≈4 km satellite of Saturn)<ref name="sheppard-saturn" /> and about 25 million times fainter than what can be seen with the naked eye.
+25.3	Trans-Neptunian object Template:Mpl	seen from Earth	Furthest known observable object in the Solar System about Template:Convert from the Sun
+26.2	Trans-Neptunian object Template:Mpl	seen from Earth	200 km sized object about Template:Convert from the Sun and about 75 million times fainter than what can be seen with the naked eye.
+27.7	Faintest objects observable with a single 8-meter class ground-based telescope such as the Subaru Telescope in a 10-hour image<ref>What is the faintest object imaged by ground-based telescopes? Template:Webarchive, by: The Editors of Sky Telescope, 24 July 2006</ref>
+28.2	Halley's Comet	seen from Earth (2003)	in 2003 when it was Template:Convert from the Sun, imaged using 3 of 4 synchronised individual scopes in the ESO's Very Large Telescope array using a total exposure time of about 9 hours<ref name="ESO2003">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
+28.4	asteroid Template:Mpl	seen from Earth orbit	observed magnitude of ≈15-kilometer Kuiper belt object seen by the Hubble Space Telescope (HST) in 2003, dimmest known directly observed asteroid.
+29.4	JADES-GS-z13-0	seen from Earth	Discovered by the James Webb Space Telescope. One of the furthest objects discovered.<ref name="Robertson2022">Template:Cite journal</ref> Approximately a billion times fainter than can be observed with the naked eye.
+31.5	Faintest objects observable in visible light with Hubble Space Telescope via the EXtreme Deep Field with ≈23 days of exposure time collected over 10 years<ref>Template:Cite journal</ref>
+35	unnamed asteroid	seen from Earth orbit	expected magnitude of dimmest known asteroid, a 950-meter Kuiper belt object discovered (by the HST) passing in front of a star in 2009.<ref name="hstoccultation">Template:Cite news</ref>
+35	star LBV 1806−20	seen from Earth	a luminous blue variable star, expected magnitude at visible wavelengths due to interstellar extinction

See also

• Angular diameter
• Distance modulus
• List of nearest bright stars
• List of nearest stars
• Luminosity
• Surface brightness

External links

• {{#invoke:citation/CS1|citation

|CitationClass=web }}