IC 4604 is a large diffuse nebula of 5th magnitude located in the southwestern corner of the constellation Ophiuchus, surrounding the bright triple star Rho Ophiuchi. Several regions of bright and dark nebulosity surround this area, which takes its name from ρ Oph.

Highlighted by the bright star Antares, the region provides an impressive spectacle of colorful glowing gases, juxtaposed with converging dark rivers of thick dust. Other areas of nebulosity within the region include IC 4603, centered around the star SAO 184376; and IC 4605, around 22 Scorpii. The nebulosity around Antares itself (α Sco) is designated IC 4606. Dark nebulae Barnard 45 and Barnard 42 separate the reflection nebulosity near ρ Oph (IC 4603 and IC 4604) from the nebulosity closer to 22 Sco and Antares (IC 4605 and IC 4606). Barnard 44 lies to the east.

At a distance of some 540 light-years, IC 4604 is one of the nearest star-forming regions to the Sun. The colorful clouds surrounding Rho Ophiuchi represent the visible counterpart of a much larger but invisible molecular cloud permeating the region. This Ophiuchus cloud lies well above the plane of the galaxy, near the border of the Scorpius-Centaurus OB association. About 1.5 million years ago, a massive star in upper Scorpius exploded as a supernova, sending a powerful shock wave through the Ophiuchus cloud about 1 million years ago, triggering star formation that is still continuing today.

(quote from SkySafari)

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Date and Place 2015-05-13 Oborotaki, Fukushima
Scope Takahashi Epsilon180ED + BetaSGR Focuser
Mount Celestron CGEM
Camera Atik383L+
Auto guiding Off-axis Superstar + GPUSB
Filter Astrodon Tru-balance Gen.2 LRGB Filter 36[mm] Unmounted
Exposure L : 18x 600[s]
R : 4x 420[s], G : 4x 420[s], B : 9x 420[s]
Total : 271[min]
Software Astroart5 SP3 with SHS Version 4.0 beta 1
PHD Guiding 2.3.1
Sky Safari Pro 4.0.5
Stella Image 6Photoshop