One certain signal that summer time is nearly over and longer autumnal nights are taking up from extra balmy late-summer evenings is the grand look in September’s late-evening southern sky of the Nice Sq. of Pegasus, the winged-horse’s acquainted asterism (star sample). The Sq. is nicely up within the jap sky as astronomically darkish skies fall at mid-month and its centre culminates at round 1am BST (midnight UT) at a really beneficial altitude of 60 levels.
The way to observe
The 4 stars marking the corners of the Sq. all shine at second- or third-magnitude, so it’s simple to see it even from light-polluted areas. Rookies typically comment that the Sq. seems bigger than anticipated; it spans roughly 15 levels alongside both sides and is about 20 levels throughout diagonally.
Solely three of the celebrities truly belong to Pegasus. The highest-left (north-eastern) star of the Sq. is alpha (α) Andromedae (Alpheratz), the brightest star within the constellation Andromeda. At one time it had two designations, alpha Andromedae and delta (δ) Pegasi, however when the constellation boundaries had been outlined by the Worldwide Astronomical Union (IAU) in 1922, Alpheratz was assigned to Andromeda and the identify delta Pegasi fell into disuse (a minimum of by skilled astronomers). The three different stars of the Sq. are among the many brightest within the constellation: magnitude +2.45 Markab (alpha [α] Pegasi) lies on the backside proper (south-western) nook), magnitude +2.4 Scheat (beta [β] Pegasi) sits at prime proper (north-west), and magnitude +2.8 Algenib (gamma [γ] Pegasi) marks the underside left (south-eastern) nook.
Mendacity throughout the Sq., about 2.5 levels north-west of Algenib, is NGC 7814 (Caldwell 43), a really good edge-on galaxy shining at magnitude +10.5. It’s generally known as the ‘Little Sombrero’, as it’s paying homage to the magnificent Sombrero Galaxy (Messier 104) in Virgo, however NGC 7814 is far smaller, spanning solely 6.3 × 2.6 arcminutes. NGC 7814 is a simple seize for a 150mm (six-inch) telescope.
NGC 7741 is one other galaxy situated throughout the confines of the Sq., discovered 6 levels south-west of Alpheratz. It’s a horny imaging goal, however is an actual problem for a 250mm (10-inch) telescope, glowing at magnitude +11.4, a magnitude or so fainter than NGC 7814, throughout its 4 x 2.8 arcminute type.
One remaining goal of observe throughout the Sq. is the galaxy grouping of NGC 7769, 7770 and 7769. The previous and latter are good eleventh-magnitude spirals that may be noticed by apertures within the 250-300mm (10- to 12-inch) vary, however the actual attraction is the group’s attractiveness in deep photos.
How darkish’s your sky?
A superb measure of your sky high quality is to rely the variety of stars you could see throughout the Nice Sq. of Pegasus – not together with the nook stars of the Sq. itself. You may work out your limiting magnitude based on the variety of stars seen utilizing the next desk.
| Seen naked-eye stars inside sq. | Limiting magnitude | Sky situations |
| 1 | 4.5 | Poor |
| 4 | 5 | Common |
| 7 | 5.5 | Good |
| 13 | 6 | Excellent |
| 35 | 6.5 | Glorious |
