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aperture_photometry

Differential aperture photometry on ctx.image (photutils).
Category Advanced
Backend photutils - wraps photutils (optional extra reduction)
Version 1.0.0
Reads ctx.image (an ImageFrame)
Writes extras.photometry, metrics.target_flux

Provide the target's (x, y) pixel coordinates and one or more comparison stars. The differential magnitude for each comparison is -2.5 * log10(target_flux / comp_flux); positive means the target is fainter than the comparison.

Parameters

Parameter Default Required Description
target_xy None yes Target (x, y) pixel coordinates (length-2 list).
comparison_xy None yes List of (x, y) coordinates for comparison stars.
aperture_radius 5.0 - Aperture radius (pixels) for source extraction.
annulus_in_radius 8.0 - Inner radius of the sky annulus (pixels).
annulus_out_radius 12.0 - Outer radius of the sky annulus (pixels).

Use it

from spectro_kernel import run_algorithm

output = run_algorithm("aperture_photometry", ctx, {
    "target_xy": "<value>",
    "comparison_xy": "<value>",
    "aperture_radius": 5.0,
    "annulus_in_radius": 8.0,
    "annulus_out_radius": 12.0
})

The CLI loads a single 1-D spectrum with --input; this algorithm needs ctx.image (an ImageFrame). Run it from Python or as a step of a pipeline preset.

{
  "tool": "aperture_photometry",
  "arguments": {
    "session_id": "<session_id>",
    "params": {
      "target_xy": "<value>",
      "comparison_xy": "<value>",
      "aperture_radius": 5.0,
      "annulus_in_radius": 8.0,
      "annulus_out_radius": 12.0
    }
  }
}

Every algorithm is an MCP tool of the same name; describe_algorithm returns this page's metadata as JSON.

References

  • Bradley et al. — Astropy Photutils (https://photutils.readthedocs.io/).
  • AAVSO Guide to CCD Photometry.
  • disentangle_sb2 - Separate the spectra of the two components of an SB2 spectroscopic binary.
  • doppler_tomogram - Doppler tomogram of a binary from N phase-resolved spectra.