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Tegmine — Double Star in Cancer

HIP 40167; Zeta1 Cancri; 16 Cancri

Observable Double Star Fair (28/100)

Sep: 1.1", Companion: mag 6.2

Magnitude 5.6m DoubleStar Cancer (Cnc) Visible
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Observe

1Physical Properties

Magnitude 5.63
Spectral Type F8V
Star Color Yellow (B-V 0.54)
Distance 84 ly

2Position & Identifiers

RA 08h 12m 12.7s
Dec +17° 38' 52.0"
Constellation Cancer (Cnc)
HR 3208
HIP 40167
HD 68255
SAO 97646
Bayer Zeta1
Flamsteed 16 Cnc
Double Cat 6650
SIMBAD Wikipedia

3How easy to split?

Primary 5.6 mag Companion 6.3 mag Separation 1.1″
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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. V. hard+ V. hard+ V. hard+
150mm Newt. Hard Hard Hard
C8 203mm Hard+ Hard+ 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 200 mm reflector.

4Visibility

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Best season Dec – Feb (peak: Jan)

5Multiple Star System Quintuple

Components 5 (quintuple)
Component IDs AB
Separation 1.1″
Companion Mag 6.2
Position Angle 177°
Star Colors A: Yellow B: Yellow
Discoverer STF1196
Combined mag. and color for 3208-9-10, 4.67V, +0.53(B-V). AB 5.63 F7V, 6.02 F9V combined colors (AB), 59.7y, | a = 0.884". Component C = HR 3210.

Separation over time

Period: 59.8 y Eccentricity: 0.320 Now: 1.1", PA 347° -0.08" in 5 years
0.00" 0.33" 0.66" 0.98" 1.3" 2025 2030 2035 2040 2045 1.1"

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

Eyepiece View

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80x Dawes: 1.9″ TFOV: 0.6°
Realistic = true angular size
N E 177°

A: 5.6 · B: 6.2 · Sep: 1.1″ · PA: 177° · N up, E right

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

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6

Size Comparison

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8

Spectral Classification

9

Hertzsprung-Russell Diagram

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Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map
10

Stellar Lifecycle

11

Blackbody Spectrum

12

Stellar Absorption Spectrum

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

13

Stellar Fusion

Discover

14Stellar Notes

0.039".
Tegmen; Tegmine.
15

Light Travel Time Machine

16

Relativistic Travel

Nearby in the Sky

Other targets within a few degrees — pan your scope a little and keep exploring.

Visibility scores assume a 150 mm Newton at Bortle 4.

NGC 2563
Hard+
Bright spiral galaxy
Galaxy mag 12.3 3.9° Cancer
R Cnc
Hard+
Mira-type variable, range 6.2–11.8
Variable Star mag 7.13 6.0° Cancer
M44
NGC 2632
Easy
Scattered bright open cluster
Open Cluster mag 3.1 7.0° Cancer
Show on Map

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