Star Magnitude Converter

NISAKE GAME

Contains ads

About this app

【Please read first】
This app does not show constellations or where anything is in the sky.
It takes a magnitude and gives you a brightness ratio, and that is all.
There is no absolute magnitude, no luminosity, and no conversion to lux.

──────────

✨ Star Magnitude Converter - how much brighter is a 1st magnitude star?

Exactly one hundred times a 6th magnitude one.
Five magnitudes are a factor of a hundred: fixed in 1856, still the definition.

【From a difference in magnitude to a ratio】
Type a magnitude difference and get the brightness ratio.
One magnitude is about 2.512 times. Two and a half magnitudes are ten times.
Five are exactly one hundred, and ten are ten thousand.

【Percentages too】
"Three magnitudes fainter" means little on its own.
"Six percent of the brightness" means something.
That is why the ratio and the percentage are shown side by side.

【It works backwards】
How many magnitudes is ten times brighter? Two and a half.
Enter a ratio or a percentage and read off the difference.

【Against objects you know】
Enter an apparent magnitude and see it against the Sun, the full Moon,
Sirius, Vega and the naked-eye limit at 6th magnitude, each taken as 1.
The Sun at −26.74 is about 398,000 times the full Moon at −12.74.
The gap is exactly 14.00 magnitudes: the whole difference between day and night.

【Negative magnitudes work】
The brighter something is, the smaller the number, so the brightest are
all negative. The Sun is −26.74, the full Moon −12.74, Sirius −1.46.
A plus-minus button sits beside the input, so the sign is always one tap away.

【Enter a reference and get exactly 1.000】
Type −26.74 against the Sun and you get 1. Type 0.03 against Vega, same thing.
It holds for every reference, because you are comparing something with itself.

【Outside the range you get a dash】
Magnitude differences run from −40 to +40, apparent magnitudes from −30 to +35.
A ratio of zero or less has no magnitude at all, so it gives a dash and a
one-line reason rather than an invented number.

【Quick chart】
Magnitude differences of 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5 and 10 as ratios
and percentages. Apparent magnitudes of −27, −13, −5, −1, 0, 1, 3, 6, 10 and
20 against the Sun and against the naked-eye limit.

【Common values】
Five magnitudes, one magnitude, one fainter, three fainter, ten times brighter,
the Sun, the full Moon, Sirius, Vega, Polaris, the naked-eye limit and Pluto,
one tap each.

【A history of the last five】
Tap to bring back something you looked up. History is kept on the device
only and can be cleared at any time.

【Notes worth knowing】
Why smaller means brighter, why one magnitude is the fifth root of a hundred,
and why Sirius leads the sky only because it is close, while Canopus gives out
far more light from much further away. A guide to apparent magnitudes runs from
the Sun down to the limit of the Hubble Space Telescope.

【No account needed】
The calculation runs on your device, and the numbers you type are never sent anywhere.

──────────

NISAKE GAME makes small tools that each do one thing.

The relation between magnitude and brightness follows the definition set by
Norman Pogson in 1856.

What’s new

• An ad now appears when the app starts
• A Copy button now sits next to the result. It copies the whole line, units and all
• The history card stays hidden until there is history, so the quick charts sit higher