When is the best time to observe OP Herculis?

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

Where is OP Herculis located in the sky?

OP Herculis lies in the constellation Hercules at right ascension 17h 57m and declination +45° 21′.

What telescope do I need to follow OP Herculis?

To follow OP Herculis through its full brightness cycle (magnitude 5.8 to 6.7) you need any 7×50 or 10×50 binoculars — the star fades out of smaller apertures near minimum light.

OP Herculis — Variable Star in Hercules

Observable Variable Star Good (58/100)

Range: 5.85 - 6.73, Period: 120.5d, Type: SRB

Magnitude 5.8–6.7^m VariableStar Hercules (Her) Visible

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1Physical Properties

Magnitude 6.02

Range 5.85 - 6.73

Period 120 days

Variable Type Semi-Regular Variable (Late-type Giant)

Spectral Type M5IIbS supergiant

Star Color Red (B-V 1.64)

2Position & Identifiers

RA 17h 56m 48.4s

Dec +45° 21' 03.0"

Constellation Hercules (Her)

HR 6702

HIP 87850

HD 163990

SAO 47080

Variable ID OP Her

SIMBAD

3How easy to follow?

Magnitude 5.9 – 6.7 mag Amplitude 0.9 mag Period 120.5 d Type SRB

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Equipment	Bortle 3	Bortle 4	Bortle 5
Naked eye Naked eye	V. hard+	V. hard	Imp.
50 mm finder 50mm finder	Medium+	Medium+	Medium
150 mm telescope 150mm scope	Medium+	Medium+	Medium+

Easy Medium Hard Very hard Impossible

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

4Visibility

Set a location in User Settings to see visibility data.

Best season May – Jul (peak: Jun)

5Survey Image

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6Light Curve

7Comparison Stars for OP Her (5.8–6.7)

Nearby stable stars for estimating brightness (AAVSO)

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8

Size Comparison

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9

Compare Stars

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10

Spectral Classification

11

Hertzsprung-Russell Diagram

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

12

Stellar Lifecycle

13

Blackbody Spectrum

14

Stellar Absorption Spectrum

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

15

Stellar Fusion

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16Stellar Notes

Variable Star

SRb 5.85 - 6.73V, 7.7 - 8.3p, 120.5d.

Spectral

Technetium star.

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.

M92

NGC 6341

Easy

Large bright globular cluster

Globular Cluster mag 6.4 7.4° Hercules

NGC 6702

Medium

Elliptical galaxy

Galaxy mag 12.2 8.8° Lyra

XY Lyr

Medium

Semi-regular variable, range 5.8–6.3

Variable Star mag 6.04 9.5° Lyra

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