Copelands Septet (Hickson 57)

Hickson 57
Hickson 57: Copelands Septet in Leo; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 120+40+40+40 min LRGB; Bernese Highlands; © 2011 Radek Chromik [32]

History

This group of galaxies was discovered on 9 February 1874 by the British astronomer Ralph Copeland with Lord Rosse's 72 inch reflecting telescope in Birr Castle. [277]

Physical Properties

The visual magnitudes between 13.6 mag to 15.2 mag challenge larger amateur telescopes from approx. 14 inches to a duel. Especially the weaker galaxies of the seven are not easy to capture. NGC 3745 is one of the most difficult galaxies with 15.2 mag. NGC 3746, NGC 3748, NGC 3750, NGC 3751 and NGC 3753 have visual magnitudes of 14.2 mag, 14.8 mag, 13.9 mag, 13.9 mag and 13.6 mag. The galaxy NGC 3754, which is close to NGC 3753, is another tough nut to crack with 14.3 mag.

Revised+Historic NGC/IC Version 22/9, © 2022 Dr. Wolfgang Steinicke [277]
Name RA Dec Type bMag vMag B-V SB Dim PA z D(z) Dreyer Description Identification, Remarks
NGC 3745 11 37 44.5 +22 01 16 Gx (E-S0) 16.2 15.2 1.0 12.0 0.4 × 0.2 102 0.031565 133.3 pB, pS, R MCG 4-28-4; VV 282; Arp 320; HCG 57G; Copeland septet
NGC 3746 11 37 43.6 +22 00 35 Gx (SBab) 15.0 14.1 0.9 13.3 1.1 × 0.5 126 0.030094 127.1 pB, pS, R UGC 6597; MCG 4-28-5; CGCG 127-6; VV 282; Arp 320; HCG 57B; Copeland septet
NGC 3748 11 37 49.1 +22 01 35 Gx (SB0) 15.8 14.8 1.0 12.6 0.7 × 0.4 132 0.029407 124.2 pB, pS, R MCG 4-28-7; CGCG 127-7; VV 282; Arp 320; HCG 57E; Copeland septet
NGC 3750 11 37 51.6 +21 58 29 Gx (E-S0) 14.9 13.9 1.0 12.1 0.5 × 0.4 132 0.030291 127.9 pB, R, cbM, 1st of 3 in line MCG 4-28-8; CGCG 127-9; VV 282; Arp 320; HCG 57C; NPM1G +22.0340; Copeland septet
NGC 3751 11 37 53.9 +21 56 13 Gx (E-S0) 15.3 14.4 0.9 12.0 0.5 × 0.2 9 0.031335 132.3 F, L, E 45° UGC 6601; MCG 4-28-9; HCG 57F; Copeland septet
NGC 3753 11 37 53.8 +21 58 53 Gx (Sab) 14.5 13.7 0.8 13.4 1.7 × 0.5 117 0.029110 122.9 pB, pL, 2nd of 3 in line UGC 6602; MCG 4-28-10; CGCG 127-12; VV 282; Arp 320; HCG 57A; Copeland septet
NGC 3754 11 37 55.0 +21 59 08 Gx (Sb) 15.1 14.3 0.8 12.4 0.4 × 0.3 18 0.029944 126.4 vF, R, 3rd of 3 in line MCG 4-28-11; CGCG 127-12; VV 282; Arp 320; HCG 57D; IRAS 11352+2216; Copeland septet

Finder Chart

The galaxy septet is located in the constellation Leo. At the back left of Leo, near δ Leonis (Zosma) on the extension of two stars with 4.5 mag (93 Leonis) and 5.2 mag (92 Leonis) the septet can be found. In the large-field eyepiece (1° and more true field of view) a row of three 9th to 8th magnitude stars points the way to the galaxy group.

Finder Chart Copelands Septet (Hickson 57)
Copelands Septet (Hickson 57) in constellation Leo. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Visual Observation

350 mm Aperture: The somewhat distant galaxy NGC 3751 can be easily and reliably recognized with a 14-inch device with averted vision. In the first group of three with NGC 3750/53/54, verifying the faint galaxy NGC 3754 is difficult because it almost merges with the neighboring galaxy NGC 3753. In the second group of three with NGC 3746/45/48 the middle galaxy NGC 3745 with 15.2 mag is at the same time the weakest and most difficult galaxy.

To see all seven galaxies, you need an extremely transparent sky and a larger amateur telescope. With an aperture of 14 inches, the lower limit is certainly exhausted. More aperture makes all galaxies more safely accessible and verifiable. [192]

14" PWO-Dobson, F:4.6 / TV-Nagler 13mm, 123x, 0.67° und TV-Radian 8mm, 200x, 0.3°
Eduard von Bergen, 2005

Objects Within a Radius of 15°

References