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Type: galaxy pair
Mag: B=15.3, V=?
Size: 0.204′ x 0.204′
NGC 5721, 5722, 5723, and 5724. The brightest three of this small group of six galaxies were found by William and John Herschel, the other three by Lord Rosse and his observer at the time, Johnstone Birney. Fortunately, the Birr Castle observers provide a diagram, so the galaxies can be positively identified, even though Dreyer's estimated NGC postions are not quite correct. MCG got all the numbers right, but the double nebula, CGCG 248-016, is incorrectly labeled as NGC 5721 + NGC 5723; it should be NGC 5721 + NGC 5722.
Is NGC 5724 the faintest positively identified NGC galaxy? It looks to be about 18th magnitude on the blue POSS1 print. There may be other such faint objects lurking among Lord Rosse's observations, but I don't recall seeing them.
The RNGC (Sulentic and Tifft 1973) notes that this is a 15.5 mag galaxy. Their coded description reads E,R,BM,ALMSTEL.
The Messier objects
The Bennett objects
The Caldwell list
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