Click on the image for a full resolution version
See this image also on Instagram
IC 4685, located approximately 4,000 light-years away from our Sun, is an often overlooked emission nebula. It shines mostly in red, due to the excitation of hydrogen gas by energetic ultraviolet radiation from nearby hot young stars. It lies in the same area as the Lagoon Nebula, M8 (located less than one degree west of it), and the Trifid Nebula, M20. Please see a wide field image of all three. These partners are brighter and famous enough to quickly and predominantly catch the astrophotographers’ attention away from IC 4685. But this nebula is attractive for many reasons. One of them is the difficulty of getting a good reproduction of the nebula, even in narrowband. This is mostly due to the presence of a remarkably beautiful and faint blue reflection nebula, IC 1274. Another reason is the conspicuous presence, as in its neighbor M20, of three nebula types: emission, reflection and dark nebulas.
This image contains several objects. On the upper right of the image is the reflection nebula IC 1274, just left of the 8th magnitude star HD 165999 (the brightest in this image). Just to the lower left of IC 1274 you can find a blob of red emission nebula, IC 1275. IC 4685 is the larger region in the center, which is crossed by the dark “river” B303. The bright red nebula on the left (East) is NGC 6559, topped by a blue reflection patch that gives it the appearance of a colorful cosmic flower. The strangely shaped and very bright planetary nebula PK006-02.1 is the cherry on top of the cake. In order to capture the reflection nebulas, broadband blue images were taken and blended together with the OIII and Halpha narrowband images. The narrowband images account for the amount of detail that can be seen, especially in IC 4685 and the “river” area.
Object
Name(s): IC 4685
Type: Emission/Reflection Nebula
RA: 18h 09m 24s
Dec: -23º 58’ 58”
Constellation: Sagittarius
Size (arcmin): 70×50
Magnitude: +7.2
Distance: 4,000 ly
Image
Date: 2023-04-05 to 2023-05-02
Location: Obstech, Río Hurtado, Chile
Size (arcmin): 34×48 arcmin
Telescope: 24” f/6.5 Reflector
Camera: QHY 461 (11760x8896pix)
Guiding: off-axis guider
Total exposure: 56h 20m (Ha: 24h; OIII: 21h 20m; RGB: 11h)
Processing: CCDStack, PixInsight (one process) and Photoshop CC 2023