Limiting Magnitude | British Astronomical Association
The Stellar Magnitude System
Apparent magnitude m is a measure of the relative brightness of a star or other astronomical objects as seen by an observer. An object's apparent magnitude depends on its intrinsic luminosity , its distance , and any extinction of the object's light by interstellar dust along the line of sight to the observer. The magnitude scale is an inverse logarithmic relation, where a difference of 1. The brighter an object appears, the lower its magnitude.
I have question about limiting magnitude of my kit. Looking at the Minor Planets Center website most of the asteroids listed above 19th magnitude in the V-Band. Last weekend decided to hunt for some faint asteroids. Cartes du Ciel said that there would be 3 20th magnitude asteroids in the field of view of a galaxy I was imaging. I double checked the ephemeris on the MPC website none of the asteroids required further observations; therefore I assumed that they had stable orbits.