When is the best time to observe HIP 101909?

HIP 101909 is best observed from June through August, with peak visibility during July when it transits around midnight in the Northern Hemisphere.

Where is HIP 101909 located in the sky?

HIP 101909 lies in the constellation Delphinus at right ascension 20h 39m and declination +15° 50′.

What telescope do I need to split HIP 101909?

Splitting HIP 101909 requires an aperture of roughly 60 mm or larger — the components are separated by about 39.9″ at magnitudes near 6.0. The companion is about 5.3 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 101909 — Double Star in Delphinus

DoubleStar Delphinus (Del) Visible

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Observe

1Physical Properties

Magnitude 5.97

Spectral Type B3V

Star Color Blue-white (B-V -0.14)

2Position & Identifiers

RA 20h 39m 05.0s

Dec +15° 50' 17.0"

Constellation Delphinus (Del)

HR 7899

HIP 101909

HD 196775

Double Cat 14106

SIMBAD

3How easy to split?

Primary 6.0 mag Companion 11.3 mag Separation 39.9″

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

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 Quintuple

Components 5 (quintuple)

Component IDs AC

Separation 39.9″

Companion Mag 11.3

Position Angle 122°

Star Colors A: Blue-white

Discoverer BU 288

Notes

AB optical. B, 13v at 7".

Separation over time

Measured 1913 → 2012 (99 y)

Separation drift 43.9" → 39.9" (-4.00")

Rate -0.0404" / y

PA drift 279° → 122° (-157°, -1.586°/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.