Resolution and Sampling
Know what the aperture can resolve.
Compare the telescope's diffraction limit with your camera sampling and local seeing. Change any input to see the consequences immediately.
Purpose and method
What this calculator does
Am I over- or under-sampled? Compare diffraction, seeing and camera sampling.
In words: Pixel scale is pixel pitch divided by focal length using the angular conversion constant.
Use the effective focal length after reducers or Barlows, the camera's native pixel pitch, the selected binning and a realistic local seeing estimate.
Working geometry
Diffraction and sampling
The atmospheric and diffraction spot is sampled by the camera pixel grid.
Inputs
Optical path
Use physical dimensions and canonical units for the estimate.
Calculated now
Resolution and sampling
These are ideal optical estimates, not a guarantee of image detail.
- Rayleigh limit
- 0.692″at 550 nm
- Dawes estimate
- 0.580″empirical double-star limit
- Image scale
- 0.776″ / px3.76 µm effective pitch
- Pixels per Rayleigh limit
- 0.89undersampled
- Pixels per seeing FWHM
- 2.58for 2.0″ seeing
- Critical focal ratio
- f/11.22,241 mm for 2 px
Equations
The Rayleigh limit is the ideal diffraction separation. The detector samples that scale with the image scale; two pixels per Rayleigh limit is the minimum target used here, while seeing usually becomes the practical limit from the ground.
Atmospheric turbulence, focus, obstruction, tracking, contrast, processing, and target brightness can all reduce real-world resolution. Treat these outputs as planning guidance.