AST / CALC Urquhart / capability
Astronomy calculator
Calculate sampling and field of view.
Enter telescope focal length, camera pixel size and sensor dimensions. The calculation runs only in this browser and sends no values to UDS.
Calculated result
Enter valid positive values.
- Image scale
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- Horizontal field
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- Vertical field
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- Diagonal field
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Image scale is a geometric calculation, not a prediction of final image quality. Seeing, guiding, focus, optics and processing still matter.
Method
Transparent formulae, bounded interpretation.
Image scale = 206.265 × pixel size (µm) ÷ focal length (mm), expressed in arcseconds per pixel.
Field of view = 2 × arctan(sensor dimension ÷ (2 × focal length)), converted to degrees.
Use actual effective focal length and active sensor dimensions where reducers, barlows or crop modes change the system.