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Magnification Formula:
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Telescope magnification (also known as power) is the factor by which a telescope enlarges the apparent size of celestial objects. It is calculated by dividing the focal length of the objective lens or mirror by the focal length of the eyepiece.
The calculator uses the magnification formula:
Where:
Explanation: The formula shows that magnification increases with longer objective focal lengths and decreases with longer eyepiece focal lengths.
Details: Proper magnification calculation helps astronomers select appropriate eyepieces for different observing conditions and targets. Higher magnification isn't always better - it can reduce image brightness and clarity, especially in poor atmospheric conditions.
Tips: Enter both focal lengths in millimeters. The objective focal length is typically specified by the telescope manufacturer, while eyepiece focal lengths are marked on the eyepiece itself.
Q1: What is the practical limit for telescope magnification?
A: A general rule is 50x per inch of aperture (2x per mm), though atmospheric conditions often limit usable magnification to 200-300x even with large telescopes.
Q2: Can I use any eyepiece with any telescope?
A: Most modern telescopes use standardized eyepiece barrels (1.25" or 2"), but you must ensure compatibility with your telescope's focuser size.
Q3: Why does higher magnification make images dimmer?
A: Higher magnification spreads the same amount of light over a larger area, reducing surface brightness. Exit pupil size decreases with higher magnification.
Q4: What magnification is best for planetary viewing?
A: Typically 150-250x works well for planets, depending on telescope aperture and atmospheric conditions.
Q5: How does Barlow lens affect magnification?
A: A Barlow lens multiplies the effective focal length of the telescope, typically by 2x or 3x, thereby increasing the magnification with any given eyepiece.