what does it mean for a digit to be significant
Significant figures The significant figures of a number are digits that carry meaning contributing to its measurement resolution. This includes all digits except:[1]
Magnitude (astronomy) The scale is logarithmic and defined such that each step of one magnitude changes the brightness by a factor of the fifth root of 100, or approximately 2.512. For example, a magnitude 1 star is exactly a hundred times brighter than a magnitude 6 star, as the difference of five magnitude steps corresponds to 2.5125, or 100.