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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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Workshop

Dust shadow distance calculator

AllField of viewSamplingImage scaleFocal ratioFocal length for seeingEyepieceBinocularsResolving powerDust shadowGuide scope

Your flat

px

Camera

µm
Binning

Focal ratio

f/5.00 from 600 mm and 120 mm aperture

Dust to sensor
2.3mm
Donut on the sensor
0.45 mm
Focal ratio used
f/5.00

The dust sits roughly 2.26 mm in front of the sensor.

d = donut·p·b / 1000·F = 120·3.76·1 / 1000·5.00 = 2.3 mm

Geometric estimate for a small particle; it does not identify the dusty surface.