0 naked eye: difficult if near bright summer evening star
artificial lights but generally Vega; C/1996 B2
visible even from large cities (Hyakutake) at peak
+1 naked eye: brilliant as seen from planet Saturn
dark, rural areas
+2 naked eye: difficult but visible from stars of Big Dipper
small cities and suburbs; diffuse Halley's comet in
objects such as comets may require 1986 near peak
small binoculars from urban areas
3 naked eye: rural, suburban, small city faintest naked-eye
binoculars: bright, urban areas stars visible from
many smaller
cities/inner
suburbs;
4 naked eye: (outer) suburbs faintest naked-eye
binoculars: cities (stars), suburban stars visible from
areas (diffuse objects such as comets) many smaller
cities/(outer)
suburbs
5 generally binocular objects from urban moons of Jupiter
and suburban areas; faintest naked-eye
stars visible from "dark" rural areas
located some 40 miles (60 km) from
major cities
6 binocular objects from suburban areas; planet Uranus
faintest naked-eye stars visible from
"dark" rural areas located some 100
miles (150 km) from major cities
7 binoculars; faintest naked-eye stars brightest minor
visible from "dark" rural areas planet (asteroid)
located some 140 miles (200 km) from and about 1-2
major cities and some 30 miles (50 km) comets each year
from nearest town of population 5000
or so
8 binocular objects; from urban areas, such planet Neptune
objects may only be visible with small
telescopes
10 from dark sky, objects visible with at any given
20x80 binoculars; from brighter sites, time, there are
a larger telescope is needed usually a couple
of comets this
bright
11 general limiting visual brightness# of
comets with a 15-cm-aperture reflector
12 general limiting visual brightness# of at any given time,
comets with a 20-cm-aperture reflector there are usually a
half dozen comets
this bright
13 general limiting visual brightness# of
comets with a 25-cm-aperture reflector
14 general limiting visual brightness# of Pluto at its brightest
stars with a 20-cm-aperture reflector
15 general limiting visual brightness# of
comets with a 50-cm-aperture reflector
19 general limiting photographic brightness#
of comets with a 50-cm-aperture
reflector
21 general limiting brightness of stars with
a 60-cm-aperture reflector + CCD
22 general limiting brightness# of comets with
a CCD and 150-cm-aperture reflector
* naked-eye viewing assumes 20-20 vision (corrected or uncorrected)
# from a dark, rural site; "visual" as compared to "photographic" or
"CCD-detected"; "reflector" means "reflecting telescope"