Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add tondevrel/scientific-agent-skills --skill photutilsgit clone --depth 1 https://github.com/tondevrel/scientific-agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/tondevrel/scientific-agent-skills/photutils)<a href="https://agentmods.dev/skills/tondevrel/scientific-agent-skills/photutils"><img src="https://agentmods.dev/badge/skills/tondevrel/scientific-agent-skills/photutils/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/tondevrel/scientific-agent-skills/photutils"><img src="https://agentmods.dev/badge/skills/tondevrel/scientific-agent-skills/photutils.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00088 | $0.02635 |
| Opus 5 | $0.00044 | $0.01318 |
| Sonnet 5 | $0.00018 | $0.00527 |
| Haiku 4.5 | $0.00009 | $0.00264 |
Grade A, and why
photutils scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 297 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Photutils - Astronomical Photometry
Photutils is the modern standard for extracting quantitative data from astronomical images. It replaces legacy tools like SExtractor or DAOPHOT with a modular, Pythonic interface integrated with the Astropy ecosystem.
When to Use
- Detecting stars or galaxies in an astronomical image (DAOStarFinder, IRAFStarFinder).
- Measuring the brightness of objects using circular, elliptical, or rectangular apertures.
- Performing PSF-fitting photometry (essential for crowded stellar fields).
- Estimating and subtracting complex 2D backgrounds (sky background).
- Calculating the centroids (precise centers) of astronomical sources.
- Performing "isophotal analysis" (measuring shapes of galaxies).
- Segmentation of images based on thresholding.
Reference Documentation
Official docs: https://photutils.readthedocs.io/
GitHub: https://github.com/astropy/photutils
Search patterns: photutils.aperture, photutils.detection, photutils.background, photutils.psf
Core Principles
Background First
Accurate photometry is impossible without correct background subtraction. Photutils provides tools to estimate global and local sky levels.
Aperture vs. PSF
- Aperture Photometry: Summing pixels within a fixed shape. Best for isolated sources or galaxies.
- PSF Photometry: Fitting a mathematical model of a star to the data. Best for overlapping stars or high-precision work.
Units and WCS
Photutils is fully units-aware. If your image has WCS metadata, apertures can be defined in sky coordinates (degrees) rather than just pixels.
Quick Reference
Installation
pip install photutils
Standard Imports
import numpy as np
import matplotlib.pyplot as plt
from astropy import units as u
from photutils.detection import DAOStarFinder
from photutils.aperture import CircularAperture, aperture_photometry
from photutils.background import Background2D, MedianBackground
Basic Pattern - Detection and Aperture Photometry
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 11d ago First seen · 297 lines · 88 tokens per session scan A ed2d0b1ce58c
photutils is a skill published in the GitHub repository tondevrel/scientific-agent-skills (21 stars, last pushed 7mo ago), licensed MIT. It adds 88 tokens to every session and 2,635 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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