IC 4604 (Ophiuchus)
The blue reflection nebula IC 4604 and the triple star Rho Ophiuchi in the constellation Ophiuchus
Fig. 1 - Part of a gigantic cloud of colorful cosmic dust and gas: The blue reflection nebula IC 4604 in Ophiuchus (and the triple star Rho Ophiuchi), photographed with an 8-inch f/4 Newtonian reflector on a ZWO AM5 mount.
| Object name: | Constellation: | Coordinates: | Apparent size: | Visual brightness: |
|---|---|---|---|---|
| IC 4604 (Rho Oph. Region) | Ophiuchus | 16h26m / -23°27' | 60' x 50' | - |
IC 4604 is a blue reflection nebula associated with the triple star Rho (ρ) Ophiuchi in the constellation Ophiuchus. IC 4604 is part of the Rho Ophiuchi Region, a large, complex region of stars, emission nebulae, and dark nebulae covering an area 4.5° by 6.5°. The Rho Ophiuchi complex is only 460 light-years away, just slightly farther than the Pleiades Cluster (Messier 45). It is one of the closest star-forming regions to the Solar System.
In the same way that molecules in the Earth's atmosphere preferentially scatter the bluer portions of the Sun's light (Rayleigh Scattering), creating our blue sky, so do the dust grains that make up IC 4604 scatter the light emanating from the stars of Rho Ophiuchi (source: Wikipedia).
Technical Details:
Exposure time: 4h 51min (97x3min)
Gain: 100
Temperature: -10°C
Date: May 30/31 and June 18/19, 2025
Processing: Astro Pixel Processor (APP) and Photoshop
Calibration: Darks, flats, and bias
Equipment:
Cooled ASI 2600MC Pro camera, TeleVue Paracorr Type II coma corrector, 8" f/4 "ONTC" Newtonian telescope, ZWO AM5 Strain Wave Mount, ZWO OAG-L off-axis system, ASI 174MM Mini guide camera, ASIAIR Plus
Fig. 2 - Search chart for IC 4604. Copyright 2025 'The Mag-7 Star Atlas Project', www.siaris.net.