When is the best time to observe Alpherg?

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

Where is Alpherg located in the sky?

Alpherg lies in the constellation Pisces at right ascension 01h 31m and declination +15° 21′.

What telescope do I need to split Alpherg?

Splitting Alpherg requires an aperture of roughly 790 mm or larger — the components are separated by about 0.6″ at magnitudes near 3.6. The companion is about 3.9 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Alpherg — Double Star in Pisces

HIP 7097; Eta Piscium; 99 Piscium

Magnitude 3.6^m DoubleStar Pisces (Psc) Visible

Star Map + List + Plan

About Alpherg

Description

Alpherg, Eta Piscium, is a G-type bright giant of spectral class G7 IIIa about 347 light-years away. It shines at magnitude 3.62 and is the brightest star in the faint zodiac constellation Pisces. Alpherg has a mass of about 3.5 Suns and a radius of about 30 Suns.

Observing Tips

Alpherg marks the head of one of the two fishes of Pisces. Despite being the brightest star in its constellation, the surrounding faintness of Pisces makes finding it a minor challenge for new observers — use the Circlet asterism (the head of the other fish) as a signpost. Best observed September through December.

History

The name Alpherg comes from the Arabic "al-fargh al-thānī," meaning "the second spout" (of water, referring to Aquarius's water flowing into Pisces). The IAU adopted the name in 2016.

Fun Facts

Pisces is the dimmest zodiac constellation; none of its stars shine brighter than magnitude 3.6. Alpherg's relatively modest brightness reflects the general faintness of the constellation — no blazing lumineries, but a full star-pattern that wraps around a significant section of the ecliptic.

Observe

1Physical Properties

Magnitude 3.62

Spectral Type G7IIIa bright giant

Star Color Orange (B-V 0.97)

Distance 347 ly

2Position & Identifiers

RA 01h 31m 29.0s

Dec +15° 20' 45.0"

Constellation Pisces (Psc)

HR 437

HIP 7097

HD 9270

SAO 92484

Bayer Eta

Flamsteed 99 Psc

Double Cat 1199

SIMBAD Wikipedia

3How easy to split?

Primary 3.6 mag Companion 7.5 mag Separation 0.6″

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 790 mm reflector.

4Visibility

Set a location in User Settings to see visibility data.

Best season Sep – Nov (peak: Oct)

5Multiple Star System

Separation 0.6″

Companion Mag 7.5

Position Angle 62°

Star Colors A: Orange

Discoverer BU 506

Notes

CPM.

Separation over time

Measured 1878 → 2008 (130 y)

Separation drift 1.0" → 0.60" (-0.40")

Rate -0.0031" / y

PA drift 13° → 62° (+49°, +0.377°/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.