Detector Angular Field Of View
Compute centered rectilinear detector field of view using exact pinhole angles, rather than a small-angle plate-scale product.
Description
A centered rectilinear detector spans a pinhole angular field determined by its dimensions and focal length.
A centered rectilinear detector spans a pinhole angular field determined by its dimensions and focal length. Exact tangent geometry differs from a simple linear plate-scale product for a wide field.1
Compute centered rectilinear detector field of view using exact pinhole angles, rather than a small-angle plate-scale product.
When to use Detector Angular Field Of View
Use this tool to compute centered rectilinear detector field of view using exact pinhole angles, rather than a small-angle plate-scale product.
Prepare the source, detector or coordinate measurements. Confirm frame, epoch, angular units, axis directions and the stated RA proper-motion convention before entering values.
How to use Detector Angular Field Of View and understand its results
- Prepare the source, detector or coordinate measurements. Confirm frame, epoch, angular units, axis directions and the stated RA proper-motion convention before entering values.
- Enter detectorWidthMm, detectorHeightMm, focalLengthMm using the field table and calculation rules, then run the tool.
- Read widthDegrees, heightDegrees. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| detectorWidthMm | Detector width mm | number | Required |
| detectorHeightMm | Detector height mm | number | Required |
| focalLengthMm | Focal length mm | number | Required |
Enter positive detector width, height and focal length, all in mm. The tool separately evaluates the horizontal and vertical angular spans and returns degrees. Different dimensions can produce unequal fields.
axisFOV=2atan(detectorDimension/(2focalLength)) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| widthDegrees | Width degrees | number |
| heightDegrees | Height degrees | number |
{
"input": {
"detectorWidthMm": 2,
"detectorHeightMm": 1,
"focalLengthMm": 10
},
"output": {
"widthDegrees": 11.421186274999286,
"heightDegrees": 5.724810452223495
}
}Limitations and assumptions
Distortion, vignetting, detector rotation and usable image margins are not modeled. The result is centered pinhole geometry and does not extract dimensions or focal length from image metadata.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Cd Matrix Image Axis Angles: Infer both image-axis angles in the WCS tangent plane from CD columns, exposing skew rather than assuming an orthogonal scalar rotation. For a complementary task, use Anisotropic Psf Sampling: Screen measured PSF FWHM sampling independently along both pixel axes using a supplied minimum; the two-pixel heuristic is not an exact Gaussian bandlimit.
References
-
Detector Angular Field Of View — tool.io
Similar or alternative tools
- Cd Matrix Image Axis Angles
Infer both image-axis angles in the WCS tangent plane from CD columns, exposing skew rather than assuming an orthogonal scalar rotation.
- Anisotropic Psf Sampling
Screen measured PSF FWHM sampling independently along both pixel axes using a supplied minimum; the two-pixel heuristic is not an exact Gaussian bandlimit.