When is the best time to observe HIP 100288?

HIP 100288 is best observed from June through August, with peak visibility during July when it transits around midnight in the Northern Hemisphere.

Where is HIP 100288 located in the sky?

HIP 100288 lies in the constellation Sagittarius at right ascension 20h 20m and declination -29° 12′.

What telescope do I need to split HIP 100288?

Splitting HIP 100288 requires an aperture of roughly 60 mm or larger — the components are separated by about 27.3″ at magnitudes near 6.3. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 100288 — Double Star in Sagittarius

Magnitude 6.3^m DoubleStar Sagittarius (Sgr) Visible

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Observe

1Physical Properties

Magnitude 6.30

Spectral Type A4/7V

Star Color White (B-V 0.17)

2Position & Identifiers

RA 20h 20m 28.1s

Dec -29° 11' 50.0"

Constellation Sagittarius (Sgr)

HR 7764

HIP 100288

HD 193281

SAO 189164

Double Cat 13702

SIMBAD

3How easy to split?

Primary 6.3 mag Companion 7.6 mag Separation 27.3″

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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 Quintuple D: optical

Components 5 (quintuple)

Component IDs AC

Separation 27.3″

Companion Mag 7.5

Position Angle 321°

Star Colors A: White C: Orange

Discoverer HJ 5188

Notes

Component C, photometric spectral class A2IV, vsini 53k/s. Component B, 10.1V at 4.1". For component AB, Rakos and | Mermilliod give 6.93V, +0.28(B-V), +0.24(U-B). However, other sources give the following V magnitudes: | Comp. 1976 1978 1980 Preferred | Gronbech and Oblak Ruffener | Olsen | AB 6.635 6.610 6.608 6.61 | C 7.724 7.706 7.72 | Colors converted from the uvby system (Gronbech and Olsen) are AB +0.13(B-V), +0.185(U-B); C +0.165(B-V), +0.14(U-B).

Separation over time

Measured 1834 → 2018 (184 y)

Separation drift 25.0" → 27.3" (+2.30")

Rate +0.0125" / y

PA drift 323° → 321° (-2°, -0.011°/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.