Crescent Nebula
The Crescent Nebula - lower right (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by Friedrich Wilhelm Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.
It is a rather faint object located about 2 degrees SW of Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity.
Imaging telescope: Takahashi FSQ130ED
Imaging camera: ASI 2600MM
Mount: JTW Trident P75
Guiding telescope: Takahashi FS60CB
Guiding camera: QHY 5 II
Focal Extender / Reducer: None
Software: Sequence Generator Pro SGP (for capture) PHD 2 (guiding), Astro Pixel Processor, PixInsight.
Filters: Astrodon Ha (3nm), OIII (3nm) and Astrodon SII (3nm). Astrodon R,G,B.
Accessories: Robofocus Focuser controlled by Lunatico Armadillo, ATIK EFW 3, RB Focus Gaius, RB Focus Excalibur.
Dates: 21st Jun. - 3rd Jul. 2024
Frames: (Total)
Astrodon Ha 30 x 600"
Astrodon OIII 36 x 600"
Astrodon SII 3 0 x 600"
Astrodon RGB 3 x 20 x 60"
Total integration = 17 Hours
Center (RA, Dec): (303.358, 38.531)
Center (RA, hms): 20h 13m 25.822s
Center (Dec, dms): +38° 31' 51.836"
Size: 77.5 x 51.7 arcmin
Radius: 0.776 deg
Pixel scale: 1.19 arcsec/pixel
Orientation: Up is 359.5 degrees E of N
It is a rather faint object located about 2 degrees SW of Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity.
Imaging telescope: Takahashi FSQ130ED
Imaging camera: ASI 2600MM
Mount: JTW Trident P75
Guiding telescope: Takahashi FS60CB
Guiding camera: QHY 5 II
Focal Extender / Reducer: None
Software: Sequence Generator Pro SGP (for capture) PHD 2 (guiding), Astro Pixel Processor, PixInsight.
Filters: Astrodon Ha (3nm), OIII (3nm) and Astrodon SII (3nm). Astrodon R,G,B.
Accessories: Robofocus Focuser controlled by Lunatico Armadillo, ATIK EFW 3, RB Focus Gaius, RB Focus Excalibur.
Dates: 21st Jun. - 3rd Jul. 2024
Frames: (Total)
Astrodon Ha 30 x 600"
Astrodon OIII 36 x 600"
Astrodon SII 3 0 x 600"
Astrodon RGB 3 x 20 x 60"
Total integration = 17 Hours
Center (RA, Dec): (303.358, 38.531)
Center (RA, hms): 20h 13m 25.822s
Center (Dec, dms): +38° 31' 51.836"
Size: 77.5 x 51.7 arcmin
Radius: 0.776 deg
Pixel scale: 1.19 arcsec/pixel
Orientation: Up is 359.5 degrees E of N
Sky Map & Finding Chart
SII, Ha & OIII in the image;
Annotated Image:
