When is the best time to observe HIP 399?

HIP 399 is best observed from August through October, with peak visibility during September when it transits around midnight in the Northern Hemisphere.

Where is HIP 399 located in the sky?

HIP 399 lies in the constellation Pegasus at right ascension 00h 05m and declination +26° 39′.

What telescope do I need to split HIP 399?

Splitting HIP 399 requires an aperture of roughly 60 mm or larger — the components are separated by about 13.1″ at magnitudes near 6.2. The companion is about 4.5 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 399 — Double Star in Pegasus

Magnitude 6.2^m DoubleStar Pegasus (Peg) Visible

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Observe

1Physical Properties

Magnitude 6.25

Spectral Type K4IIIb bright giant

Star Color Red (B-V 1.40)

2Position & Identifiers

RA 00h 04m 56.0s

Dec +26° 38' 56.0"

Constellation Pegasus (Peg)

HR 9109

HIP 399

HD 225276

SAO 73731

Double Cat 42

SIMBAD

3How easy to split?

Primary 6.3 mag Companion 10.7 mag Separation 13.1″

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

Easy Medium Hard Very hard Impossible

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

4Visibility

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Best season Aug – Oct (peak: Sep)

5Multiple Star System

Separation 13.1″

Companion Mag 10.7

Position Angle 149°

Star Colors A: Red

Discoverer FOX 103

Separation over time

Measured 1895 → 2015 (120 y)

Separation drift 23.4" → 13.1" (-10.30")

Rate -0.0858" / y

PA drift 121° → 149° (+28°, +0.233°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

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.