Magnitude (in astronomy, stargazing, and astrophotography) is simply a measure of the brightness of an astronomical (celestial) object (e.g., a star like Betelgeuse or a galaxy like Andromeda galaxy).
Why is it important for an amateur (professional) astronomer, stargazer, and astrophotographer? It's straightforward - the brighter the object, the easier it is to spot, gaze, and photograph!
There are two types of magnitude in astronomy: apparent and absolute. In our hobby, we mainly use the apparent one - the brightness as it appears to our eyes on the night sky, not the absolute "quantity"/"amount" of light that a particular celestial object "produces" objectively.
How is Calculated
There are two facts about the magnitude that may be counterintuitive for a newcomer to the hobby:
- It is "reversed" - the smaller the number, the brighter the celestial object appears on the night sky.
- It can be negative.
Look at the table below.
Magnitude Examples on Different Astronomical Objects
Here I curated a few interesting astrophotography and stargazing objects in order of their magnitude. I sorted from the brightest to the dimmest (non-visible).
|Astronomical Object||Apparent Magnitude|
|International Space Station (ISS)||-6|
|Mars and Jupiter||-3|
|Vega and Saturn||0|
|Polaris (North Star)||2|
|North America Nebula||4|
|Naked Eye Limit||6|
|Limit of the Hubble Telescope||32|
It's important to remember that there is one more important factor in stargazing and astrophotography than magnitude itself - the clear, dark sky. It can be hard to spot even bright objects like Pleiades or Orion Nebula on a highly light-polluted night sky in a city. If you live in a town area like me, then get into the car, drive some distance from the center, and enjoy astronomy as it should be - without (or with greatly reduced) artificial light. Use this fantastic map to find dark-sky spots in your area.