WhatTheStar

M 70 Deep sky · Globular cluster in Sagittarius · M 70 · NGC 6681

M 70

A small globular cluster at the foot of the Teapot — where Alan Hale and Thomas Bopp both spotted the great comet that took their names.

Finder chart of M 70: about 6° of sky with north up and east to the left, M 70 ringed at the centre, stars to magnitude 6.5, with Kaus Australis, Ascella and Kaus Media named, and M 54 and M 69 marked. M 70Kaus AustralisAscellaKaus MediaM 54M 69
About 6° of sky, north up and east to the left, as you see it facing that way. Stars to magnitude 6.5.

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Type
Globular cluster
Designations
M 70 · NGC 6681
Constellation
Sagittarius
Apparent magnitude
9.1
Apparent size
8′
Position (J2000)
RA 18h 43m · Dec −32° 18′

The full Moon, about 31′ across, is 3.9 times as wide. The Sun passes 9° from it around late December, and for about 23 days of the year it sits within 15° of the Sun, lost in its glare.

Survey photograph of M 70: 14′ of sky, north up and east to the left, with the stars around it taken out
14′ of sky, north up and east to the left: the picture the sky map lays in as you zoom in, its stars taken out so the map’s own show through. Photo: DSS2 colour (STScI / Caltech / AAO; colour and HEALPix by CDS). Licence: DSS: © Caltech, AAO/UKSTU and AURA, by agreement; HiPS © CNRS/Unistra (ODbL).

When to see it

On the night of Wed 30 Jun 2027, when it is highest around midnight, on each city’s own clock:

FromRisesHighestSets
London GMT+1 22:40 01:10 · 6° 03:39
New York EDT 21:17 01:04 · 17° 04:52
Singapore GMT+8 19:19 01:15 · 56° 07:11
Sydney GMT+10 16:27 00:06 · 88° 07:45

Common questions

Can I see it from 50° north?
Only just. At its highest it is 8° above the southern horizon, so it needs a clear, flat view that way and clean air.
Can I see it from 35° south?
Yes, and well placed: at its highest it passes almost overhead, 87° up, above most of the air’s haze.
When is the best time of year to see it?
Around late June, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late September it is highest in the early evening, and in late March not until the hours before dawn.
How bright is it?
Magnitude 9.1 in total, but that light is spread over 8′ of sky: on average 22.2 magnitudes per square arcsecond. Against a dark country sky that average stands out; a city’s glow drowns all but its brightest parts.
Naked eye, binoculars or telescope?
Binoculars. At magnitude 9.1 it is past the eye, but a 50 mm pair under a dark sky reaches about magnitude 11.0.

Look for

It lies on the line between Kaus Australis and Ascella, along the Teapot’s bottom, east of M 69.

Look for

From 50° north it barely clears the horizon, at 8°; from 35° north it climbs to 23°; from the equator it climbs to 58°; from 35° south it climbs to 87°.

Look for

Magnitude 9.1 against the faintest star each can show: the eye under a city sky, 4.5 (4.6 short); the eye under a dark country sky, 7.0 (2.1 short); 50 mm binoculars under that dark sky, 11.0 (2.0 to spare); a 100 mm telescope there, 12.5 (3.5 to spare). Those limits are for a point of light; its light is spread over its whole size, so it needs some of that margin in hand. Through 7×50 binoculars, whose field is about 7.1° across, it spans 2% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 13% of the field’s width.

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