Hickson 57, Copelands Septet
History
This group of galaxies was discovered on February 9, 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.
| Name | RA [hms] | Dec [dms] | mType | Dim ['] | Btot [mag] | HRV [km/s] | PA [°] |
|---|---|---|---|---|---|---|---|
| NGC 3746, HICK 57B | 11 37 43.6 | +22 00 33 | SBRM | 1.1 x .5 | 14.8 | 9025 | 127 |
| NGC 3745, HICK 57G | 11 37 44.6 | +22 01 15 | L M | .4 x .2 | 16.1 | 9413 | |
| NGC 3748, HICK 57E | 11 37 49.1 | +22 01 33 | L M | .7 x .4 | 15.7 | 8989 | |
| NGC 3750, HICK 57C | 11 37 51.7 | +21 58 26 | L M | .8 x .7 | 14.9 | 9064 | |
| NGC 3753, HICK 57A | 11 37 53.8 | +21 58 51 | S M | 1.7 x .5 | 14.5 | 8717 | 120 |
| NGC 3751, HICK 57F | 11 37 54.0 | +21 56 10 | L M | .8 x .5 | 15.3 | 9592 | 5 |
| NGC 3754, HICK 57D | 11 37 55.1 | +21 59 08 | S M | .4 x .3 | 14.7 | 9012 |
Finder Chart
The galaxy septet is located in the constellation Leo. Left behind on the lion, near δ Leonis on the extension of two stars with 4.5 mag and 5.2 mag is the septet.
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]