When is the best time to observe Arkab Prior?

Arkab Prior is best observed from June through August, with peak visibility during July when it transits around midnight in the Northern Hemisphere.

Where is Arkab Prior located in the sky?

Arkab Prior lies in the constellation Sagittarius at right ascension 19h 23m and declination -44° 28′.

What telescope do I need to split Arkab Prior?

Splitting Arkab Prior requires an aperture of roughly 60 mm or larger — the components are separated by about 28.3″ at magnitudes near 4.0. The companion is about 3.2 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Arkab Prior — Double Star in Sagittarius

HIP 95241; Beta1 Sagittarii

Observable Double Star Good (58/100)

Sep: 28.3", Companion: mag 7.2

Magnitude 4.0^m DoubleStar Sagittarius (Sgr) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.01

Spectral Type B9V

Star Color Blue-white (B-V -0.10)

2Position & Identifiers

RA 19h 22m 38.3s

Dec -44° 27' 32.0"

Constellation Sagittarius (Sgr)

HR 7337

HIP 95241

HD 181454

SAO 229646

Bayer Beta1

SIMBAD Wikipedia

3How easy to split?

Primary 4.0 mag Companion 7.2 mag Separation 28.3″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
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

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Best season Jun – Aug (peak: Jul)

5Multiple Star System

Separation 28.3″

Companion Mag 7.2

Companion Sp F0V

Position Angle 76°

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

Discoverer DUN 226

Notes

CPM. Companion A5V; vsini 129k/s, optical?

Separation over time

Measured 1826 → 2015 (189 y)

Separation drift 30.0" → 28.3" (-1.70")

Rate -0.0090" / y

PA drift 60° → 76° (+16°, +0.085°/y)

Slow change over generations — observable in lifetime comparisons.

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.