When is the best time to observe Rho Herculis?

Rho Herculis is best observed from May through July, with peak visibility during June when it transits around midnight in the Northern Hemisphere.

Where is Rho Herculis located in the sky?

Rho Herculis lies in the constellation Hercules at right ascension 17h 24m and declination +37° 09′.

What telescope do I need to split Rho Herculis?

Splitting Rho Herculis requires an aperture of roughly 100 mm or larger — the components are separated by about 3.9″ at magnitudes near 4.5. Larger apertures and steady seeing help resolve the pair cleanly.

Rho Herculis — Double Star in Hercules

HIP 85112; Rho Herculis; 75 Herculis

Observable Double Star Excellent (66/100)

Sep: 3.9", Companion: mag 5.4

Magnitude 4.5^m DoubleStar Hercules (Her) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.52

Range 4.54 - 4.56

Period 3.3 days

Variable Type Alpha2 CVn (Magnetic Rotating)

Spectral Type B9.5III giant

Star Color Blue-white (B-V -0.03)

2Position & Identifiers

RA 17h 23m 41.0s

Dec +37° 08' 45.0"

Constellation Hercules (Her)

HR 6485

HIP 85112

HD 157779

SAO 66001

Bayer Rho

Flamsteed 75 Her

Double Cat 10526

SIMBAD Wikipedia

3How easy to split?

Primary 4.5 mag Companion 5.4 mag Separation 3.9″

Sign in and configure your equipment and default location to see a personalized row.

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Medium+	Medium+	Medium+
150 mm Newton 150mm Newt.	Easy	Easy	Easy
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season May – Jul (peak: Jun)

5Light Curve

6Multiple Star System Triple C: optical

Components 3 (triple)

Component IDs AB

Separation 3.9″

Companion Mag 5.4

Position Angle 320°

Star Colors A: Blue-white B: Yellow-white

Discoverer STF2161

Notes

Binary with HR 6484. Combined colors. Combined mag. 4.17V.

Separation over time

Measured 1821 → 2023 (202 y)

Separation drift 4.5" → 3.9" (-0.60")

Rate -0.0030" / y

PA drift 308° → 320° (+12°, +0.059°/y)

Essentially fixed on human timescales — the same view your grandchildren will see.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.