Numbers
Helpful Numbers and Formulas
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Determine Magnification
Magnification = Focal Length / Eyepiece Diameter
If you are using a 20 mm eyepiece and the Focal Length of your scope is 700 mm then 700 mm/20 mm = 35x
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Calculate f ratio
f ratio = Focal Length / Aperture
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Calculate Field of View (FOV)
FOV = AFOV (Apparent Field of View) / Magnification
AFOV :: Plossl = 50 Degrees, Nagler = 82 Degrees, Panoptic = 68 Degrees, Radian = 60 Degrees
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Magnitude
The smaller the number, the brighter the object. A star with a magnitude of -1 is brighter than a star with a magnitude of 1.
Some interesting information on how magnitude is determined can be found here.
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Longitude and Latitude of my Backyard
Longitude: -76.535531
Latitude: 36.779288
+36° 46′ 45.44″, -76° 32′ 7.91″
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Distance and Speed
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AU (Astronomical Unit) – Mean (Mathematical Average) distance of the Earth from the Sun – 149,597,870.7 kilometers or 92,955,807 miles – It takes about 499 seconds (8.32 minutes) for light to travel 1 AU
LD (Lunar Distance) – Average distance from Earth to the Moon – 384,403 kilometers or 238,857 miles
Light Year – Distance light travels in a vacuum in 1 year (365.25 days) – 9,460,730,472,580.8 kilometers or (about) 5,878,630,000,000 miles which is equal to about 63,241.1 AU
Speed of Light (or Light Speed) – Distance light travels in 1 second – 299,792,458 meters/second or 186,000 miles/second
