10-inch Newtonian, StarlightXpress MX716, 38 minutes
The Arp includes both the low surface brightness galaxy and the small high surface brightness companion; it is in the LSB Spirals class. A reduced-contrast enlargement of the companion shows some of the inner detail, while the very faint, looping arms are better seen in the higher-contrast image. The Atlas notes comment that "not known if both galaxies are at the same distance".
Arp 4 has probably been the source of more frustration than any other Arp, for both visual and CCD observers. As a result of errors in the professional catalogs that went largely unnoticed until Dennis Webb did his research in 1995, most, if not all, of the chart-generating programs mistakenly identify NGC 599 and 601 as Arp 4. While they are a somewhat unusual galaxy pair, they aren't Arp 4. Arp 4 is actually MGC-2-5-50 and A. There are several similar errors in the catalogs but the others reflect confusion among several small adjacent galaxies -- almost any imaging setup is going to include the correct galaxy within the field.