Deep-sky tour

Take in magnificent galaxies in the vicinity of Triangulum, the Triangle

1 M33

M33 is a magnificent, albeit faint spiral galaxy in Triangulum. Although listed at mag. +5.7 it’s hard to see. M33 is face-on to us and with an apparent size of 62 x 39 arcminutes, its surface brightness is low. Locate it by extending the line from M31, the Andromeda Galaxy, through Mirach (Beta (b) Andromedae) for the same distance again. A small scope under dark skies will show the central core as a misty fuzzball. A 250mm scope shows a mottled patchwork of dim light surrounding the core.  SEEN IT

2 Collinder 21 Our next target has a charm all its own. To locate it, start at Rasalmothallah (Alpha (a) Trianguli). Head 2.4˚ south and 0.7˚ west, where you’ll find a mag. +8.1 star with a curve of 10th magnitude stars to its north. This is the cluster Collinder 21. The semi-circle has a diameter of 6 arcminutes. A small scope reveals six stars here, a 250mm instrument increasing the count to 14.  SEEN IT

3 NGC 672 (and IC 1727)

Heading 0.6˚ northwest from the brightest star in Collinder 21 brings you to NGC 672, a spiral galaxy located 23.4 million lightyears away. A 150mm scope reveals the object to be elongated, with a hint of brightness at its centre. With a visual magnitude of +10.8 and a size 6.6 x 2.7 arcminutes, like M33, NGC 672 suffers from low surface brightness. This is an interacting galaxy, deformed by gravitational forces inflicted by IC 1727, a mag. +12.1 irregular galaxy located 6 arcminutes to the west. A 250mm instrument reveals NGC 672 to be 4 arcminutes long and 1.5 arcminutes wide.  SEEN IT

4 NGC 777

We head inside the pointed isosceles triangle that is Triangulum for our next

This Deep-Sky Tour has been automated ASCOM-enabled Go-To mounts can now take you to this month’s targets at the touch of a button, with our Deep-Sky Tour file for the EQTOUR app. Find it online.

View the Triangulum Galaxy, M33, through a 250mm telescope to reveal the mottled patchwork of the spiral galaxy target, the 12th magnitude elliptical galaxy NGC 777. It’s visible in a 150mm instrument, despite its dim magnitude, but again dark skies are recommended. To locate it, imagine the middle line of the Triangulum triangle starting at Rasalmothallah. Head 2.4˚ along this line from Rasalmothallah where you’ll find a mag. +8.7 star with a mag. +9.3 star 6.5 arcminutes to the west: TYC2308-878-1 and TYC2308-585-1 respectively. NGC 777 forms a right-angled triangle with these stars, TYC2308-585-1 at the right angle. The galaxy lies 4.7 arcminutes from TYC2308585-1 in a direction away from Rasalmothallah. It’s dim in a 150mm instrument, a misty patch with a star-like nucleus; and is 1 arcminute across in a 250mm scope.  SEEN IT

5 NGC 784

For our penultimate target, the virtually edge-on barred spiral galaxy NGC 784, head 2.3˚ southeast of Rasalmothallah to locate mag. +6.6 HIP 9493. You’ll find NGC 784 28 arcminutes to the north of this star. Again, this galaxy is listed at a reasonably bright mag. +11.8 but suffers from low surface brightness. A 150mm scope will show it as a faint scratch of light orientated north-south. A large scope is necessary to do it justice, the galaxy appearing 6 arcminutes long and nearly an arcminute wide through a 300mm instrument. The mistiness of the galaxy’s elongated halo surrounds a brighter inner region roughly 1.5 arcminutes in length. Through larger instruments, there’s a definite mottled texture across the galaxy’s length.  SEEN IT

6 NGC 890

Our final target is NGC 890, an 11th magnitude lenticular galaxy sitting 1.1˚ east-southeast of Gamma (g) Trianguli in a barren area of sky. The best strategy to locate it is to use the short edge of Triangulum formed by drawing a line from Beta (b) through Gamma Trianguli. Keep this line going for about half the distance again and you’ll be in the right area. Listed with an integrated magnitude of +11.1, a 150mm instrument sees it as a slightly elongated glow. A 250mm scope reveals an object approaching 2 arcminutes in length and 1 arcminute wide under dark-sky conditions.  SEEN IT

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