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Plan

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

Tools

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

Setup

  • Settings
  • About & Support
  • What’s new

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Sky & timeNew

Planetary imaging calculator

Which Barlow, and how long can I record?

All 16 calculators
Polar alignmentTripod trailingSky darknessPlanetary imaging

Planet

″

Telescope

mm
mm

Camera

µm

Telescope, camera and sky are shared by every calculator in this visit and kept in the link.

Needs a strong BarlowDrawn to scale

Target focal ratio

f/18.8

With 3.76 µm pixels aim for about f/19 (critical sampling f/13.7). Record Jupiter for up to 291 s before its rotation blurs 1.15″ detail.

Barlow needed
3.76×
Planet disc
131 px
Capture before rotation blurs
291 s

With your numbers

F ≈ 5·p = 5·3.76 = f/18.8 (2p/λ = f/13.7)

18.8 / 5.00 = 3.76×

t = r·P·3600 / (π·D) [disc-centre speed π·D/P] = 1.15·9.93·3600 / (π·45.0) = 291 s

f ≈ 5 × pixel size is the common practical target; diameters change through the year, so enter tonight's. Derotation software allows longer captures.