NGC 6540 — Open Cluster in Sagittarius
Fair (21/100)
Observe
1Properties
Magnitude
15.0
Angular Size
4.1′
pF, S, iE, er or Cl
Querying SIMBAD database...
Position & Identifiers
2How easy to spot?
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. | Imp. | Imp. | Imp. |
| 150 mm Newton 150mm Newt. | V. hard | Imp. | Imp. |
| Celestron C8 (203 mm SCT) C8 203mm | V. hard | V. hard | Imp. |
Easy
Medium
Hard
Very hard
Impossible
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
Stretch
on Seestar S50
3Visibility
Set a location in User Settings to see visibility data.
Best season
May – Jul
(peak: Jun)
4
Eyepiece View
5
Best Magnification
Explore
6
Classification Decoder
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 6520
Open cluster
Open Cluster
mag 8.0
0.6°
Sagittarius
Gamma Sgr
HIP 88567; Gamma1 Sagittarii
Pulsating variable, period 7.6d
Variable Star
mag 4.69
1.8°
Sagittarius
NGC 6553
Globular cluster — dense ball of ancient stars
Globular Cluster
mag 8.3
2.0°
Sagittarius
M8
Lagoon Nebula
Emission nebula — try an OIII filter
Emission Nebula
mag 4.6
3.4°
Sagittarius
NGC 6530
Rich open cluster
Open Cluster
mag 4.6
3.4°
Sagittarius
Collinder 367
Open cluster
Open Cluster
mag 6.4
4.0°
Sagittarius
NGC 6451
Open cluster
Open Cluster
mag 8.0
4.2°
Scorpius
Explore Nightbase
Related knowledge, tools, and stories — no observation planning required.
The Hertzsprung-Russell Diagram — Reading Stars Like a Map
The HR diagram turns the night sky into a physics map: every named star has a spot, every spot tells you mass, age, and fate. A guide for amateur observers.
Article
Sagittarius
Mythology, bright stars, and deep-sky highlights.
Constellation
Saturn
Rings, divisions, and the jewel of the outer Solar System.
Deep dive
