When is the best time to observe Rotanev?

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

Where is Rotanev located in the sky?

Rotanev lies in the constellation Delphinus at right ascension 20h 38m and declination +14° 36′.

What telescope do I need to split Rotanev?

Splitting Rotanev requires an aperture of roughly 440 mm or larger — the components are separated by about 0.5″ at magnitudes near 3.6. Larger apertures and steady seeing help resolve the pair cleanly.

Rotanev — Double Star in Delphinus

HIP 101769; Beta Delphini; 6 Delphini

Magnitude 3.6^m DoubleStar Delphinus (Del) Visible

Star Map + List + Plan

About Rotanev

Description

Rotanev, Beta Delphini, is the brightest star in the small but distinctive constellation Delphinus. It is an F-type subgiant of spectral class F5 IV about 101 light-years away, paired spectroscopically with an F-type companion in a 26.66-year orbit. The pair is just barely within the reach of speckle interferometry at its widest separation (0.5 arcseconds). Combined magnitude is 3.63.

Observing Tips

Rotanev marks the southwest corner of the tiny diamond of Delphinus, one of the sky's most charming small constellations. Binoculars readily show the diamond pattern. The spectroscopic binary within Rotanev is too close to split visually; the primary appears as a steady pale yellow-white point. Best observed July through November.

History

The name Rotanev — along with its partner Sualocin at Alpha Delphini — famously hides a signature: both names read in reverse give "Nicolaus Venator," a Latinized version of the name Niccolò Cacciatore, the assistant astronomer to Giuseppe Piazzi at Palermo Observatory in the early 1800s. Cacciatore quietly named the two stars after himself in the 1814 Palermo Catalogue, and the names have stuck.

Fun Facts

Rotanev's hidden etymology went undetected for decades; the trick was only spotted by British astronomer Thomas William Webb in 1859. Today Rotanev and Sualocin remain the only IAU-recognized star names known to be deliberate Latin-reversed self-tributes by their cataloger.

Observe

1Physical Properties

Magnitude 3.63

Spectral Type F5IV subgiant

Star Color Yellow-white (B-V 0.44)

Distance 101 ly

2Position & Identifiers

RA 20h 37m 33.0s

Dec +14° 35' 43.0"

Constellation Delphinus (Del)

HR 7882

HIP 101769

HD 196524

SAO 106316

Bayer Beta

Flamsteed 6 Del

Double Cat 14073

SIMBAD Wikipedia

3How easy to split?

Primary 3.6 mag Companion 5.0 mag Separation 0.5″

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

Easy Medium Hard Very hard Impossible

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

To reach "Medium" at Bortle 3, you'd need at least a 440 mm reflector.

4Visibility

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Best season Jun – Aug (peak: Jul)

5Multiple Star System Quintuple

Components 5 (quintuple)

Component IDs AB

Separation 0.5″

Companion Mag 5.0

Companion Sp F2V

Position Angle 320°

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

Discoverer BU 151

Notes

AB 4.0 F5IV, 4.9 F5IV, 26.65y, a = 0.475" or 26.60y, a = 0.480". Speckle interferometry gives sep. 0.58" and with SB | data leads to masses 2.2 and 1.8 solar. Combined mag., colors. Components C-E optical.