'((3 6.< TOUR
We search out the celestial wonders amidst the Eagle’s tail feathers
Tick the box when you’ve seen each one 1 NGC 6751
All of this month’s Deep-Sky Tour objects are located around the region of sky representing the lower body and tail of Aquila, the Eagle. The first is planetary nebula NGC 6751, which can be found at the southern apex of a squat isosceles triangle that uses mag. +3.4 Lambda (h) and mag. +4.0 12 Aquilae as its base. NGC 6751 is around 12th magnitude, with a central star shining at mag. +13.9. It can be seen in a 6-inch scope, but its small (10 arcsecond) diameter is best revealed with larger instruments. A 10-inch scope at 250x magnification shows a circular, ring-like object with a bright centre that gently fades away towards the outer ring. Larger scopes still begin to show dark mottling, which becomes especially evident south of the core. Ĵ SEEN IT
2 NGC 6790
Our next object is NGC 6790, another planetary located farther up Aquila’s body, close to the centre of a triangle formed by mag. +3.4 Delta (b), mag. +4.6 Nu (i) and mag. +5.1 23 Aquilae. At mag. +10.7, this nebula shouldn’t give much trouble for larger instruments, but it is challengingly small at just 7 arcseconds. Its size tends to make it appear quite star-like at low magnifications, so don’t be afraid to up the power. Like many planetaries, NGC 6790 responds well to the use of UHC or OIII filters. The latter can be used to confirm you’ve got it via the ‘blink technique’: pass an OIII filter between your eye and eyepiece and the nebula should maintain its brightness while the stars dim. Do this several times and the star-like nebula should become obvious. Ĵ SEEN IT
3 NGC 6760
A much easier nearby object for smaller scopes is globular cluster NGC 6760. It an be found 4º southwest of Delta Aquilae and at mag. +8.8 should be easy to locate. Its identification is further assisted by a small asterism of stars nearby forming a squashed pentagon, in which NGC 6760 marks the northern point. A 6-inch scope shows a 2-arcminute diameter haze with a mottled granularity. Under good conditions, 150x magnification should resolve some of the cluster’s stars. Increased aperture delivers extra detail, although even a 10-inch scope doesn’t resolve everything. This size of scope shows NGC 6750 to be almost double the size shown through a 6-inch instrument. The larger aperture also reveals a slight east-west elongation. Ĵ SEEN IT
4 NGC 6741
Planetary nebula NGC 6741, also known as the Phantom Streak Nebula,
is 2.5º southwest of NGC 6760. This is an 11th-magnitude object with an overall size of 9x7 arcseconds. Once again, given its size, this object is best suited for larger apertures, NGC 6741 appearing quite starlike at lower powers. A magnitude +12.7 star sits just north of the nebula’s centre. At powers below 300x it’s difficult to separate the nebula and star, especially as the dimmer star is a good match for the surface brightness of the nebula. It is 7,000 lightyears from Earth, and has a distinctly elongated and somewhat rectangular appearance when photographed with professional telescopes. Ĵ SEEN IT
5 NGC 6704
Our last two objects are easy small telescope targets. The first is open cluster NGC 6704, situated approximately one-quarter of the way along the line from Beta (`) Scuti towards 12 Aquilae. Here we’ve left Aquila, hopping next door into Scutum. Despite being located against rich Milky Way starfields, these aren’t that obvious through smaller apertures, resulting in the cluster appearing with surprisingly few field stars around it. It contains around 71 members, which together give it an integrated magnitude of +9.2. A 6-inch scope reveals a mostly hazy patch with just a few stars showing individually. Six of these form a distinctive wedge-shaped asterism that can be used to positively identify the cluster. Ĵ SEEN IT
6 M11
Our final target is M11, the Wild Duck Cluster. It resides in Scutum and can be found by extending the curve formed by Lambda and 12 Aquliae through mag. +4.8 Eta (d) Scuti. M11 is 1.5º westsouthwest of Eta and should be just visible to the naked eye. A 6-inch scope shows around 150 stars, and as you increase the aperture the view gets steadily more breathtaking, with many stars appearing clumped into knots and strings. Its name comes from a V-shape of stars that resembles the pattern formed by flying wild ducks. In total this cluster, 6,000 lightyears distant, is estimated to contain 2,900 stars, 500 of which are brighter than mag. +14.0. Ĵ SEEN IT