Deep-sky tour
We explore the border region between the constellations of Cygnus and Cepheus
1 IC 1396
First up is the visually difficult nebula, IC 1396. Occupying a roughly circular area in southern Cepheus, the orange variable star Erakis (Mu (m) Cephei) sits on its north-northeast edge. IC 1396 stretches 2.5˚ southsouthwest of this star. The nebula is visually difficult due to low surface brightness. It contains the open cluster Trumpler 37 and the lovely triple Struve 2816 (Σ2816) at the region’s centre.
A dark sky combined with a rich-field 150mm or larger scope will give the best results. Use a low power eyepiece and an OIII (oxygen) visual filter. SEEN IT
2 vdB 142 The object vdB 142 (IC 1396A) is a dark region within IC 1396. Double star Σ2813 sits centrally within vdB 142. A number of knots of brighter emission material mark the nebula’s borders, especially to the west and it’s this bright, thin outline that best defines vdB 142. Rotated so east is at the top, the nebula resembles an elephant’s head and has become known as the Elephant’s Trunk Nebula. The nebula’s ‘bright’ outline is due to gas ionised by the massive star HD 206267, the brightest component of Σ2816. To see the outline you’ll need dark skies and a large scope. SEEN IT
3 M39
M39 is easy to observe; first, head north of Erakis to mag. +4.3 Nu (η) Cephei and then reverse direction, moving from Nu Cephei through Erakis and continuing for around 4.5 times that distance again to arrive at M39. Mag. +4.0 Rho (r) Cygni lies 2.8˚ south of the cluster.
M39 is large at 32 arcminutes across. Visually it resembles a squashed kite. The brightest star shines at mag. +6.6. A close pair (mag. +7.7 and +8.8) sits at the centre of the pattern. At 40x magnification, the kite shape is surrounded by a field of fainter stars. SEEN IT 4 Sh 2-125
Sharpless 2-125, the Cocoon Nebula, is a reflection and emission nebula in northern Cygnus. Measuring 12 arcminutes across, it shines at mag. +7.2 but is tricky to see due to low surface brightness. A hydrogen-beta filter gives a better view. It co-resides with IC 5146, a cluster of mag. +9.5 stars. IC 5146/Sharpless 2-125 sits 3.5˚ east and 1.3˚ south of M39. Extending a line from mag. +4.7 Pi1 Cygni through mag. +4.2 Pi2 Cygni for the same distance brings you into the Cocoon Nebula’s general area. SEEN IT
5 NGC 7000
NGC 7000, the North America Nebula, has a photographic shape resembling that of North America. Listed as a fourth magnitude object, this is misleading. With an apparent size of 120x100 arcminutes, it has low surface brightness, magnification tending to look right through it.
Head 4.4˚ east-southeast of Deneb to arrive at mag. +3.7 Xi (ξ) Cygni. Heading back along this line towards Deneb, NGC 7000’s width occupies a little less than half the line’s length. The southern half of the ‘continent’ appears brightest, a dark region forming the Gulf of Mexico providing excellent contrast with the glowing nebula. The brighter eastern edge of this region forms what’s known as the ‘Cygnus Wall’. The use of an OIII or UHC filter under dark-sky conditions, combined with a rich-field scope and low magnification are key to seeing any detail in NGC 7000. SEEN IT
6 IC 5070
If you fancy a slightly more challenging object, then IC 5070 will be right up your street. Location-wise this emission nebula couldn’t be easier, because it’s next to NGC 7000 to the west. It has a listed apparent magnitude of +8.0 and like its better-known neighbour NGC 7000 it’s large, which leads to low surface brightness. IC 5070, also known as the Pelican Nebula, has a size of 60x50 arcminutes. The main portion (the Pelican’s head and beak) sits between 57 Cygni (mag. +4.8) and 56 Cygni (mag. +5.0). The brightest part of the nebula (IC 5067), and thus the best observing region, sits slightly northwest of the mid-point of the line joining both stars. Again, a dark sky and a rich-field telescope on low power are recommended here. SEEN IT