Catalog Modules

starward provides Python access to major astronomical catalogs for deep-sky objects and bright stars.

Available Catalogs

Module	Catalog	Objects	Description
messier	Messier	110	Classic deep-sky catalog
ngc	NGC	~7,840	New General Catalogue
ic	IC	~5,386	Index Catalogue
caldwell	Caldwell	109	Patrick Moore's catalog
hipparcos	Hipparcos	~9,100	Bright star catalog

Common Interface

All catalog modules share a consistent interface:

# Singleton instance
CATALOG.get(number)           # Get object by number
CATALOG.list_all()            # List all objects
CATALOG.search(query)         # Search by text
CATALOG.filter_by_type(type)  # Filter by object type
CATALOG.filter_by_constellation(code)  # Filter by constellation
CATALOG.filter_by_magnitude(max_mag)   # Filter by brightness
CATALOG.stats()               # Catalog statistics

# Coordinate functions
catalog_coords(number)        # Get ICRSCoord
catalog_altitude(number, observer, jd)  # Current altitude
catalog_transit_altitude(number, observer)  # Transit altitude

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Messier Catalog

The 110 Messier objects—the finest deep-sky objects visible from mid-northern latitudes.

Basic Usage

from starward.core.messier import MESSIER, messier_coords

# Get the Andromeda Galaxy
m31 = MESSIER.get(31)
print(f"{m31.name}: {m31.object_type}")
print(f"Magnitude: {m31.magnitude}")
print(f"Constellation: {m31.constellation}")

# Get coordinates
coords = messier_coords(31)
print(f"RA: {coords.ra.hours:.4f}h")
print(f"Dec: {coords.dec.degrees:.4f}°")

MessierObject Properties

Property	Type	Description
number	int	Messier number (1-110)
name	str	Common name
object_type	str	Type (galaxy, nebula, cluster, etc.)
constellation	str	IAU 3-letter code
ra_hours	float	Right ascension in hours
dec_degrees	float	Declination in degrees
magnitude	float	Visual magnitude
size_arcmin	float	Angular size in arcminutes
distance_kly	float	Distance in thousands of light-years
ngc	int	NGC catalog number

Searching and Filtering

from starward.core.messier import MESSIER

# Search by name or description
results = MESSIER.search("orion")
results = MESSIER.search("ring nebula")

# Filter by type
galaxies = MESSIER.filter_by_type("galaxy")
globulars = MESSIER.filter_by_type("globular_cluster")
planetaries = MESSIER.filter_by_type("planetary_nebula")

# Filter by constellation
sgr_objects = MESSIER.filter_by_constellation("Sgr")

# Filter by brightness
naked_eye = MESSIER.filter_by_magnitude(6.0)
binocular = MESSIER.filter_by_magnitude(8.0)

Visibility Calculations

from starward.core.messier import messier_altitude, messier_transit_altitude
from starward.core.observer import Observer
from starward.core.time import jd_now

observer = Observer.from_degrees("Home", 40.7, -74.0)
jd = jd_now()

# Current altitude
alt = messier_altitude(31, observer, jd)
print(f"M31 altitude: {alt.degrees:.1f}°")

# Maximum altitude (at transit)
transit_alt = messier_transit_altitude(31, observer)
print(f"M31 transit altitude: {transit_alt.degrees:.1f}°")

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NGC Catalog

The New General Catalogue—the primary professional deep-sky reference.

Basic Usage

from starward.core.ngc import NGC, ngc_coords

# Get the North America Nebula
ngc7000 = NGC.get(7000)
print(f"{ngc7000.name}: {ngc7000.object_type}")

# Get M31 by NGC number
ngc224 = NGC.get(224)
print(f"NGC 224 is {ngc224.name}")

# Cross-reference Messier
m31_ngc = NGC.get_by_messier(31)
print(f"M31 = NGC {m31_ngc.number}")

NGCObject Properties

Property	Type	Description
number	int	NGC number
name	str	Common name (if any)
object_type	str	Object type
constellation	str	IAU 3-letter code
ra_hours	float	Right ascension
dec_degrees	float	Declination
magnitude	float	Visual magnitude
size_arcmin	float	Angular size
messier_number	int	Messier number (if applicable)

Statistics

from starward.core.ngc import NGC

stats = NGC.stats()
print(f"Total objects: {stats['total']}")
print(f"By type: {stats['by_type']}")

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IC Catalog

The Index Catalogue—a supplement to the NGC.

Basic Usage

from starward.core.ic import IC, ic_coords

# Get the Horsehead Nebula
ic434 = IC.get(434)
print(f"{ic434.name}: {ic434.object_type}")

# Famous IC objects
ic1805 = IC.get(1805)  # Heart Nebula
ic1848 = IC.get(1848)  # Soul Nebula

The IC module has the same interface as NGC.

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Caldwell Catalog

Sir Patrick Moore's 109 deep-sky objects not in the Messier catalog.

Basic Usage

from starward.core.caldwell import Caldwell, caldwell_coords

# Get the Double Cluster
c14 = Caldwell.get(14)
print(f"{c14.name}: NGC {c14.ngc_number}")

# Get the Sculptor Galaxy
c65 = Caldwell.get(65)
print(f"{c65.name} in {c65.constellation}")

CaldwellObject Properties

Property	Type	Description
number	int	Caldwell number (1-109)
name	str	Common name
object_type	str	Object type
constellation	str	IAU 3-letter code
ngc_number	int	NGC cross-reference
magnitude	float	Visual magnitude

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Hipparcos Star Catalog

Bright stars with precise astrometric data from ESA's Hipparcos satellite.

Basic Usage

from starward.core.hipparcos import Hipparcos, star_coords

# Get Sirius
sirius = Hipparcos.get(32349)
print(f"{sirius.name}: {sirius.spectral_type}")
print(f"Magnitude: {sirius.magnitude}")
print(f"Distance: {sirius.parallax_mas} mas")

# Find by name
vega = Hipparcos.get_by_name("Vega")
polaris = Hipparcos.get_by_name("Polaris")

# Find by Bayer designation
betelgeuse = Hipparcos.get_by_bayer("Alpha Orionis")

HIPStar Properties

Property	Type	Description
hip_number	int	Hipparcos catalog number
name	str	Common name
bayer	str	Bayer designation (e.g., "Alpha Lyrae")
constellation	str	IAU 3-letter code
ra_hours	float	Right ascension
dec_degrees	float	Declination
magnitude	float	Visual magnitude
spectral_type	str	Full spectral type (e.g., "A0V")
spectral_class	str	Spectral class letter (e.g., "A")
bv_color	float	B-V color index
parallax_mas	float	Parallax in milliarcseconds

Filtering by Spectral Type

from starward.core.hipparcos import Hipparcos

# Hot blue stars
b_stars = Hipparcos.filter_by_spectral_class("B")
a_stars = Hipparcos.filter_by_spectral_class("A")

# Cool red giants
k_giants = Hipparcos.filter_by_spectral_class("K")
m_giants = Hipparcos.filter_by_spectral_class("M")

# Named stars only
named = Hipparcos.filter_named()

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Object Types

Deep-Sky Object Types

Type	Description
galaxy	Spiral, elliptical, irregular galaxies
globular_cluster	Dense spherical star clusters
open_cluster	Loose stellar associations
planetary_nebula	Shells from dying stars
emission_nebula	Glowing gas clouds
reflection_nebula	Dust reflecting starlight
dark_nebula	Opaque dust clouds
supernova_remnant	Stellar explosion debris
star_cloud	Dense Milky Way regions

Spectral Classes

Class	Color	Temperature	Examples
O	Blue	>30,000 K	Very rare
B	Blue-white	10,000-30,000 K	Rigel, Spica
A	White	7,500-10,000 K	Vega, Sirius
F	Yellow-white	6,000-7,500 K	Procyon
G	Yellow	5,200-6,000 K	Sun
K	Orange	3,700-5,200 K	Arcturus
M	Red	2,400-3,700 K	Betelgeuse

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Working with Coordinates

All catalog modules provide coordinate functions returning ICRSCoord:

from starward.core.messier import messier_coords
from starward.core.ngc import ngc_coords
from starward.core.hipparcos import star_coords

# Get coordinates
m31_coords = messier_coords(31)
ngc7000_coords = ngc_coords(7000)
sirius_coords = star_coords(32349)

# Use with other calculations
from starward.core.angles import angular_separation

sep = angular_separation(
    m31_coords.ra, m31_coords.dec,
    sirius_coords.ra, sirius_coords.dec
)
print(f"Separation: {sep.degrees:.1f}°")

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Example: Building an Observing List

from starward.core.messier import MESSIER, messier_altitude
from starward.core.observer import Observer
from starward.core.time import jd_now

observer = Observer.from_degrees("Home", 40.7, -74.0)
jd = jd_now()

# Find galaxies above 30° altitude
print("Galaxies visible tonight:")
for obj in MESSIER.filter_by_type("galaxy"):
    alt = messier_altitude(obj.number, observer, jd)
    if alt.degrees > 30:
        print(f"  M{obj.number}: {obj.name} ({alt.degrees:.0f}°)")

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See Also

• Finder Module — Cross-catalog search
• Lists Module — Observation list management
• Visibility Module — Visibility calculations