When is the best time to observe 1 Bootis?

1 Bootis is best observed from March through May, with peak visibility during April when it transits around midnight in the Northern Hemisphere.

Where is 1 Bootis located in the sky?

1 Bootis lies in the constellation Boötes at right ascension 13h 41m and declination +19° 57′.

What telescope do I need to split 1 Bootis?

Splitting 1 Bootis requires an aperture of roughly 100 mm or larger — the components are separated by about 4.4″ at magnitudes near 5.8. The companion is about 3.8 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

1 Bootis — Double Star in Boötes

Magnitude 5.8^m DoubleStar Boötes (Boo) Visible

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Observe

1Physical Properties

Magnitude 5.75

Spectral Type A1V

Star Color White (B-V 0.01)

Distance 181 ly

2Position & Identifiers

RA 13h 40m 40.5s

Dec +19° 57' 20.0"

Constellation Boötes (Boo)

HR 5144

HIP 66727

HD 119055

SAO 82942

Flamsteed 1 Boo

Double Cat 8991

SIMBAD

3How easy to split?

Primary 5.8 mag Companion 9.6 mag Separation 4.4″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Hard+	Hard+	Hard+
150 mm Newton 150mm Newt.	Medium+	Medium+	Medium+
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 Mar – May (peak: Apr)

5Multiple Star System Triple C: optical

Components 3 (triple)

Component IDs AB

Separation 4.4″

Companion Mag 9.6

Position Angle 133°

Star Colors A: White B: Yellow

Discoverer STF1772

Notes

AB binary. B is Am.

Separation over time

Measured 1827 → 2019 (192 y)

Separation drift 6.0" → 4.4" (-1.60")

Rate -0.0083" / y

PA drift 140° → 133° (-7°, -0.036°/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.