When is the best time to observe Eta Fornacis?

Eta Fornacis is best observed from September through November, with peak visibility during October when it transits around midnight in the Northern Hemisphere.

Where is Eta Fornacis located in the sky?

Eta Fornacis lies in the constellation Fornax at right ascension 02h 50m and declination -35° 51′.

What telescope do I need to split Eta Fornacis?

Splitting Eta Fornacis requires an aperture of roughly 100 mm or larger — the components are separated by about 4.9″ at magnitudes near 5.9. The companion is about 4.1 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Eta Fornacis — Double Star in Fornax

HIP 13225; Eta2 Fornacis

Magnitude 5.9^m DoubleStar Fornax (For) Visible

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Observe

1Physical Properties

Magnitude 5.92

Spectral Type K0III giant

Star Color Orange (B-V 0.90)

2Position & Identifiers

RA 02h 50m 14.8s

Dec -35° 50' 37.0"

Constellation Fornax (For)

HR 848

HIP 13225

HD 17793

SAO 193940

Bayer Eta2

SIMBAD Wikipedia

3How easy to split?

Primary 5.9 mag Companion 10.0 mag Separation 4.9″

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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 Sep – Nov (peak: Oct)

5Multiple Star System

Separation 4.9″

Companion Mag 10.0

Position Angle 16°

Star Colors A: Orange

Discoverer HJ 3536

Notes

Primary G6III, secondary G4V.

Separation over time

Measured 1835 → 2016 (181 y)

Separation drift 4.0" → 4.9" (+0.90")

Rate +0.0050" / y

PA drift 4° → 16° (+12°, +0.066°/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.