When is the best time to observe 15 Delphini?

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

Where is 15 Delphini located in the sky?

15 Delphini lies in the constellation Delphinus at right ascension 20h 50m and declination +12° 33′.

What telescope do I need to split 15 Delphini?

Splitting 15 Delphini requires an aperture of roughly 60 mm or larger — the components are separated by about 105.5″ at magnitudes near 6.0. The companion is about 5.1 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

15 Delphini — Double Star in Delphinus

DoubleStar Delphinus (Del) Visible

Star Map + List + Plan Star Hop

Observe

1Physical Properties

Magnitude 5.98

Spectral Type F5V

Star Color Yellow-white (B-V 0.43)

Distance 109 ly

2Position & Identifiers

RA 20h 49m 37.8s

Dec +12° 32' 43.0"

Constellation Delphinus (Del)

HR 7973

HIP 102805

HD 198390

Flamsteed 15 Del

SIMBAD

3How easy to split?

Primary 6.0 mag Companion 11.1 mag Separation 105.5″

Sign in and configure your equipment and default location to see a personalized row.

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

Easy Medium Hard Very hard Impossible

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

4Visibility

Set a location in User Settings to see visibility data.

Best season Jun – Aug (peak: Jul)

5Multiple Star System Quadruple

Components 4 (quadruple)

Component IDs AC

Separation 105.5″

Companion Mag 11.1

Position Angle 86°

Star Colors A: Yellow-white

Discoverer BU 1495

Separation over time

Measured 1886 → 2020 (134 y)

Separation drift 109.4" → 105.5" (-3.90")

Rate -0.0291" / y

PA drift 81° → 86° (+5°, +0.037°/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.