When is the best time to observe Kurhah?

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

Where is Kurhah located in the sky?

Kurhah lies in the constellation Cepheus at right ascension 22h 04m and declination +64° 38′.

What telescope do I need to split Kurhah?

Splitting Kurhah requires an aperture of roughly 80 mm or larger — the components are separated by about 8.2″ at magnitudes near 4.3. Larger apertures and steady seeing help resolve the pair cleanly.

Kurhah — Double Star in Cepheus

HIP 108917; Xi Cephei; 17 Cephei

Observable Double Star Good (59/100)

Sep: 8.2", Companion: mag 6.4

Magnitude 4.3^m DoubleStar Cepheus (Cep) Visible

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Observe

1Physical Properties

Magnitude 4.29

Spectral Type A3/6Vm

Star Color White (B-V 0.34)

Distance 102 ly

2Position & Identifiers

RA 22h 03m 47.4s

Dec +64° 37' 40.0"

Constellation Cepheus (Cep)

HR 8417

HIP 108917

HD 209790

SAO 19827

Bayer Xi

Flamsteed 17 Cep

Double Cat 15600

SIMBAD Wikipedia

3How easy to split?

Primary 4.3 mag Companion 6.4 mag Separation 8.2″

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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 Jul – Sep (peak: Aug)

5Multiple Star System Triple C: optical

Components 3 (triple)

Component IDs AB

Separation 8.2″

Companion Mag 6.4

Position Angle 275°

Star Colors A: White B: Yellow

Discoverer STF2863

Notes

AB 4.61 A3m, 6.5 F7V or F3III-IV, 3800y, a = 11.5". Aa, 2.254y, a = 0.073". Component B is HD 209791 = GC 30876, | vsini =<25k/s. Component C, 12.7v at 97" optical.

Separation over time

Period: 2501.3 y Eccentricity: 0.749 Now: 8.2", PA 274° + 0.04" in 5 years

Apparent separation over time, computed from ORB6 orbital elements. Steep curves indicate fast-changing pairs — catch them while they're splittable.

Eyepiece View

Telescope Eyepiece

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80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 4.3 · B: 6.4 · Sep: 8.2″ · PA: 275° · N up, E right

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″

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Size Comparison

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Spectral Classification

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Hertzsprung-Russell Diagram

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Stellar Lifecycle

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Blackbody Spectrum

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Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

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Stellar Fusion

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15Stellar Notes

Spectroscopic Binary

ADS 15600A, 810.9d, K 7.1k/s, V0 -10.7k/s, msin3i 0.855, asini 70.3. sep. SB components 0.06". Resolved by | speckle interferometry. Mass transfer. Secondary undermassive for its luminosity. vsini both components 20k/s.

Group/Cluster

Hyades group.

Spectral

K/H/m yield classes A3/F1/F2 respectively.

Dynamical

0.038".

Radial Velocity

Change of 7k/s in 55y needs confirmation.

Alternative Names

Alkurhah; Al Kirdah; Kurhah.

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