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Biography
D'Arrest started his astronomical career as a 2nd assistant astronomer at Berlin Observatory (1845-48). There he discovered (together with Galle) Neptun with the 9.6" Fraunhofer refractor. Actually Galle saw the planet first, but d'Arrest used one of the new Berliner Akademische Sternkarten to mark Leverrier's postion. After this time he worked at the old Leipzig Observatory (Pleissenburg) from 1848-57 using a 4.6" f/16.8 Fraunhofer refractor (erected in 1830). In 1851 he married Auguste Emilie Möbius (1822-1897). The had a daughter and a son. A year later he became Professor of Astronomy at Leipzig University. From 1857-1875 he was at Copenhagen Observarory using a 11" f/17.5 Merz refractor.
Obituary: MNRAS 36, 155 (1876), Obs. 32, 211 (1909); AN 86, 63 (1875); VJS 11, 1 (1876)
Copenhagen Observatory and 11" f/17.5 Merz-Refractor
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Discoveries
At Leipzig (using the 4,6" Fraunhofer refractor) d'Arrest found 2 NGC objects: NGC 607 (Auwers 15) on Aug. 23, 1855, which is only a pair of stars in Cetus. And, on the same night, the asterism NGC 7005 near M 73. They are published in Resulate aus Beobachtungen der Nebelflecke und Sternhaufen (Engelmann, Leizpig 1857), cited as "R" in Tab. 1 below (column "Ref"). The first observations at Copenhagen (using the 11" Merz refractor) were published by Arthur Auwers (William Herschel's Verzeichnisse von Nebelflecken und Sternhaufen, Königsberg 1862). These objects are cited as "Auw" (plus number in Auwer's list). d'Arrest's major work on nebulae, listing 5000 observations, including precise positions measured with a ring micrometer and descriptions of 1492 objects, is Siderum Nebulosorum Observationes Havnienses (Copenhagen, 1867); cited as "SN". There are two intermediate papers: AN #1500 [63, 177 (1865)] and AN #1537 [65, 1 (1865)]. In the first, d'Arrest mentioned the Coma cluster of galaxies (where he found 25 objects).
Dreyer credits 344 objects to d'Arrest. Due to identities and considering the right historical order - if other observers are involved - the correct number of discoveries is 321:
- 8 objects, credited to others by Dreyer, are first seen by d'Arrest. Objects of Lord Rosse IV: NGC 710, 714, 717 (incorrectly credited to Lord Rosse III by Dreyer); objects of Marth: NGC 4053, 4078, 7464, 6712, 7679.
- 8 objects, credited to d'Arrest by Dreyer, are seen first by others. William Herschel: NGC 4092, 4669, 5819; Lord Rosse III: NGC 169, 394, 3016; Marth: NGC 6384, 7367.
- 23 objects, found by d'Arrest, are idential to objects, found earlier by other observers (Tab. 1, below). NGC 4886 is already counted in the "Dreyer 344", while NGC 4107 is not (see above).
| Object | Identity | Discoverer | Remarks |
| NGC 523 | NGC 537 | W. Herschel | |
| NGC 674 | NGC 697 | W. Herschel | |
| NGC 875 | NGC 867 | W. Herschel | |
| NGC 1550 | NGC 1551 | W. Herschel | |
| NGC 3144 | NGC 3174 | W. Herschel | |
| NGC 3183 | NGC 3218 | W. Herschel | |
| NGC 3235 | NGC 3234 | J. Herschel | |
| NGC 3575 | NGC 3162 | W. Herschel | |
| NGC 3760 | NGC 3301 | W. Herschel | |
| NGC 3856 | NGC 3847 | J. Herschel | |
| NGC 4046 | NGC 4045 | W. Herschel | |
| NGC 4078 | NGC 4107 | d'Arrest | NGC 4107 not counted |
| NGC 4130 | NGC 4129 | W. Herschel | |
| NGC 4140 | NGC 4077 | W. Herschel | |
| NGC 4325 | NGC 4368 | W. Herschel | |
| NGC 4338 | NGC 4310 | W. Herschel | |
| NGC 4702 | NGC 4692 | W. Herschel | |
| NGC 4797 | NGC 4798 | W. Herschel | |
| NGC 4882 | NGC 4886 | d'Arrest | NGC 4886 counted |
| NGC 4884 | NGC 4889 | W. Herschel | |
| NGC 4960 | NGC 4961 | W. Herschel | |
| NGC 5519 | NGC 5570 | W. Herschel | |
| NGC 5868 | NGC 5865 | W. Herschel |