A measure of how bright an object appears when seen from Earth. It's a logarithmic scale with a difference of 5 magnitudes corresponds to a brightness change of exactly 100. A one-magnitude change is equivalent to a brightness change of 2.512. The relationship is inverse which means that the brighter an object appears, the lower its magnitude value. The apparent magnitude of stars is measured with a bolometer.

Apparent magnitude examples include:
Sun = -26.7
Full Moon = -12.9
Venus = -4.9 (max. brightness)
Sirius = -1.5 (brightest night-time star)
Faintest stars visible to naked eye (normal conditions) = +6

Sirius the brightest night-time star (credit:- Fred Espenak)

Glossary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Sky Highlights - June 2017

Saturn
Saturn reaches opposition on June 15

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for June

Northern Hemisphere
Evening
Southwest:- Jupiter (mag. -2.2)
Southeast:- Saturn (mag. 0.0)
Midnight
West:- Jupiter
South:- Saturn
Morning
Southwest:- Saturn
Southeast:- Neptune (mag. +7.9)
East:- Venus (mag. -4.3), Uranus (mag. +5.9)

Southern Hemisphere
Evening
North:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
Morning
West:- Saturn
Northeast:- Neptune
East:- Venus, Uranus, Mercury (first half of month (mag. -0.4 to -1.2)

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

Shop at Amazon US

Contributions

If you like the website and want to contribute to the running costs then please do so below. All contributions are most welcome.

PayPal - The safer, easier way to pay online.