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ASTRONOMY FORMULAS FOR YOUR
ZHUMELL DOBSONIAN TELESCOPE
LIMITING MAGNITUDE
To determine the limiting magnitude of a telescope, use the aperture
in the following formula for an approximation.
Limiting Magnitude = 7.5 + 5LOG(Aperture in cm)
Ex: Limiting Magnitude of a 254x1250mm telescope.
Limiting Magnitude = 7.5 + 5LOG(25.4cm)
Limiting Magnitude = 7.5 + (5 x 1.405)
Limiting Magnitude = 14.52
RESOLVING POWER
To determine the resolving power of a telescope under ideal
conditions, divide the aperture into 4.56.
Resolving Power = 4.56/Aperture (in inches)
Ex: Resolving Power of a 254x1250mm telescope.
Aperture (in.) = 70mm/25.4 = 2.75 in.
Resolving Power = 4.56/10in.
Resolving Power = .456
