4 Sagittarii — Double Star in Sagittarius
Good (57/100)
Observe
1Physical Properties
Magnitude
4.76
Spectral Type
B9V
Star Color
Blue-white
(B-V -0.04)
Distance
326 ly
2Position & Identifiers
RA
17h 59m 47.6s
Dec
-23° 48' 58.0"
Constellation
Sagittarius
(Sgr)
HR
6700
HIP
88116
HD
163955
SAO
186061
Flamsteed
4 Sgr
Querying VizieR catalog...
3How easy to split?
Primary
4.8 mag
Companion
8.4 mag
Separation
3.7″
Sign in
and configure your equipment and default location to see a personalized row.
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Hard | Hard | Hard |
| 150 mm Newton 150mm Newt. | Medium+ | Medium+ | Medium+ |
| 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
Set a location in User Settings to see visibility data.
Best season
May – Jul
(peak: Jun)
5Multiple Star System
Separation
3.7″
Companion Mag
8.4
Position Angle
243°
Star Colors
A: Blue-white
B: Yellow
Discoverer
GUL 1
Eyepiece View
80x
Dawes: 1.9″
TFOV: 0.6°
Realistic = true angular size
A: 4.8 · B: 8.4 · Sep: 3.7″ · PA: 243° · N up, E right
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
6
Size Comparison
Querying VizieR for stellar data…
7
Compare Stars
8
Spectral Classification
9
Hertzsprung-Russell Diagram
Loading HR diagram…
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
14
Light Travel Time Machine
15
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.
M20
Trifid Nebula
Emission nebula — try an OIII filter
Emission Nebula
mag 6.3
1.0°
Sagittarius
NGC 6530
Rich open cluster
Open Cluster
mag 4.6
1.2°
Sagittarius
IC 4678
Diffuse nebula
Diffuse Nebula
mag 10.40
1.9°
Sagittarius
21 Sgr
Colorful double, sep 1.7″
Double Star
mag 4.81
6.8°
Sagittarius
Explore Nightbase
Related knowledge, tools, and stories — no observation planning required.
Sagittarius
Mythology, bright stars, and deep-sky highlights.
Constellation
Double Stars — A Guide for Observers
Two suns where one appeared — how to find, split, and appreciate the night sky's finest pairs. From Albireo's gold-and-blue to the Sirius B challenge.
Article
Jupiter
The Great Red Spot, cloud belts, and the Galilean moons.
Deep dive
