Celestially

Celestially is a Python package to generate astronomical finding charts for given celestial coordinates (RA/Dec). It uses astropy, matplotlib, and astroquery to fetch sky images and overlay markers for the target position.

Features

• Generate a finding chart for any sky position
• Input: RA/Dec (ICRS, J2000) or CSV file with multiple targets
• Output: PNG/JPG/PDF finding chart image
• Mark target with crosshair
• Plot proper motion vector if available
• Add image scale bar in arcseconds
• Customizable crosshair and scale bar

Installation

pip install git+https://github.com/naamach/celestially

Usage Example (Python)

from celestially import create_finding_chart

# Example coordinates (RA, Dec in degrees)
ra = 210.8023
dec = 54.3489
create_finding_chart(ra, dec, output_file='chart.png')

Command Line Usage

Generate a chart for a single object:

celestially-create 210.8023 54.3489 --output chart.png --fov 5 --survey "DSS2 Red"

Generate charts for multiple objects from a CSV:

celestially-create --csv targets.csv --fov 5 --survey "DSS2 Red"

CSV Format

The CSV file should have columns:

• name: Object name
• ra: Right Ascension (degrees)
• dec: Declination (degrees)
• pmra: Proper motion in RA (mas/yr, optional)
• pmdec: Proper motion in Dec (mas/yr, optional)

Example:

name,ra,dec,pmra,pmdec
StarA,210.8023,54.3489,10.5,-5.2
StarB,211.1234,54.5678,,

CLI Options

• --output: Output image filename (default: finding_chart.png)
• --survey: Sky survey to use (default: DSS2 Red)
• --fov: Field of view in arcminutes (default: 3.5)
• --sexagesimal: Input coordinates in sexagesimal format
• --csv: CSV file with columns: name,ra,dec[,pmra,pmdec]
• --crosshair-len: Crosshair arm length in pixels (default: 15)
• --crosshair-gap: Crosshair center gap half-width in pixels (default: 4)
• --scale-bar: Scale bar length in arcsec (default: auto)
• --format: Output image format (png, jpg, pdf, etc.)

License

MIT

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The package name "celestially" is a play on "Where's Wally" and "celestial," reflecting its purpose: creating finding charts to help you locate a specific star in an astronomical image.

This package was developed with the assistance of GitHub Copilot.