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AstroBrainCalculators
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Plan

  • Tonight
  • Targets
    • Saved targets
  • Plan a night
  • Night plans
    • Logbook

Tools

  • Sky atlas
  • Field of View
  • Night Outlook
    • Weather
  • Exposure Lab
  • Calculators
  • Horizon Studio
  • Sequence Studio
    • Nights
    • Projects

Setup

  • Settings
  • About & Support
  • What’s new

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Visual

Eyepiece calculator

AllField of viewSamplingImage scaleFocal ratioFocal length for seeingEyepieceBinocularsResolving powerDust shadowGuide scope

Object

Telescope

mm
mm
Barlow / reducer
×

Eyepiece

mm
°
Powered by Aladin Lite·CDS / Université de Strasbourg·Imagery: DSS2 (CDS)
Comfortable
Magnification
24×
True field
2.83°
Exit pupil
5.0 mm

24× shows about 2.83° of sky (5.4 full-Moon widths) with a 5.0 mm exit pupil.

M = f·B / e = 600·1.00 / 25.0 = 24.0× · TF ≈ AFOV / M = 68 / 24.0 = 2.83° · P = D / M = 120 / 24.0 = 5.00 mm

The true field is approximate; real fields depend on the eyepiece’s field stop.