When is the best time to observe Gamma Sagittarii?

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

Where is Gamma Sagittarii located in the sky?

Gamma Sagittarii lies in the constellation Sagittarius at right ascension 18h 05m and declination -29° 35′.

What telescope do I need to follow Gamma Sagittarii?

To follow Gamma Sagittarii through its full brightness cycle (magnitude 4.3 to 5.1) you need the naked eye under a dark sky — the star fades out of smaller apertures near minimum light.

Gamma Sagittarii — Variable Star in Sagittarius

HIP 88567; Gamma1 Sagittarii

Observable Variable Star Excellent (70/100)

Range: 4.28 - 5.10, Period: 7.6d, Type: DCEP

Magnitude 4.3–5.1^m VariableStar Sagittarius (Sgr) Visible

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1Physical Properties

Magnitude 4.69

Range 4.28 - 5.10

Period 7.6 days

Variable Type Classical Cepheid

Spectral Type F4-G1Ib

Star Color Yellow-white (B-V 0.78) (reddened by dust)

2Position & Identifiers

RA 18h 05m 01.3s

Dec -29° 34' 48.0"

Constellation Sagittarius (Sgr)

HR 6742

HIP 88567

HD 164975

SAO 186237

Bayer Gamma1

Variable ID W Sgr

Double Cat 11029

SIMBAD Wikipedia

3How easy to follow?

Magnitude 4.3 – 5.1 mag Amplitude 0.8 mag Period 7.59 d Type DCEP

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Equipment	Bortle 3	Bortle 4	Bortle 5
Naked eye Naked eye	Hard+	Hard	Hard
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

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Best season May – Jul (peak: Jun)

5Survey Image

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6Light Curve

7Comparison Stars for Gamma Sgr (4.3–5.1)

Nearby stable stars for estimating brightness (AAVSO)

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8

Size Comparison

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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

ADS 11029A, CDelta 4.30 - 5.08V, 7.594710d. Period changes. Spectrum and magnetic field variable. One component of | SB.

Double Star

ADS 11029A is speckle interferometric double, sep. 0.116". Visual companions, 13.5v at 33" and 13.5v at 48".

Spectroscopic Binary

80y, K 2.65k/s, V0 -27.7k/s, asini 60.

Alternative Names

Although HR 6742 and 6746 are named gamma1 and gamma2 Sgr, respectively, more often 6746 is simply called gamma Sgr | and the Greek letter is omitted for HR 6742.