Caldwell 48
C48 - Click here for full resolution
Caldwell 48, also known as NGC 2775, is a spiral galaxy located in the constellation Cancer. It is approximately 55 million light-years away from Earth. This galaxy is notable for its well-defined spiral arms and a bright central bulge, which are characteristic features of a flocculent spiral galaxy. Unlike grand-design spirals, flocculent spirals have patchy and discontinuous arms, giving them a fluffy or "woolly" appearance. NGC 2775 has a diameter of about 70,000 light-years, making it slightly smaller than our Milky Way. The galaxy's arms are rich in young, blue stars and star-forming regions, while the central bulge is dominated by older, yellow stars. Caldwell 48 is also known for its relatively low rate of star formation compared to other spiral galaxies. This galaxy was discovered by William Herschel in 1783 and is included in the Caldwell Catalogue, compiled by Sir Patrick Moore, as object number 48.
source: DeepSeek
NGC/IC:
Other Names:
Object:
Constellation:
R.A.:
Dec:
Distance to Earth:
App. Magnitude:
Transit date:
Tr. Alt (Oria, Spain):
NGC2775
n.a.
Galaxy
Cancer
09h 10m 18s
+07° 02.0′
55 million ly
10.5
25 February
60º S
Conditions
C48 is best visible during Winter. Observed from the remote observatory at IC Astronomy in Oria , Spain, it reaches a maximum altitude of 60 degrees in late February. C48 was photographed from the observatory in Spain over 6 nights during late January, early February 2025.
Equipment
The default rig at the observatory was used. The core of this rig is a Planewave CDK-14 telescope on a 10Micron GM2000 mount, coupled to a Moravian C3-61000 Pro full-frame camera. The RoboTarget module in Voyager Advanced automated the process to find optimal time-slots during astronomical night.
Telescope
Mount
Camera
Filters
Guiding
Accessoires
Software
Planewave CDK14, Optec Gemini Rotating focuser
10Micron GM2000HPS, custom pier
Moravian C3-61000 Pro, cooled to -10 ºC
Chroma 2” Luminance, Red, Green and Blue unmounted, Moravian filterwheel L, 7-position
Unguided
Compulab Tensor I-22, Windows 11, Dragonfly, Pegasus Ultimate Powerbox v2
Voyager Advanced, Viking, Mountwizzard4, Astroplanner, PixInsight 1.9.2
Imaging
C48 is a typical broadband object, and the default exposure times were used. This means 3 minutes for luminance and 5 minutes for each of the Red, Green and Blue filters. The total exposure was 20 h. Despite the small field of view of this long focal length telescope, the final image was heavily cropped to emphasise the galaxy’s structure.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Rotation
Image center
4500 x 3000 px (13.5 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
22' x 15'
-0.133°
RA: 09h 10m 20.083s
Dec: +07° 02’ 15.20”
Processing
All images were calibrated using Darks (50), Flats (50) and Flat-Darks (50), registered and integrated using the WeightedBatchPreProcessing (WBPP) in PixInsight. All further processing was done in PixInsight, including the use of scripts and tools developed by RC-Astro, SetiAstro, GraXpert, and others. For a step-by-step description of the processing techniques applied, see process flow below.
The core of the galaxy is rather bright, with fainter signal stretching out far away from the center. To capture both in the final image, an HDR technique was applied. In this case, a separate HDR clone was created using HDRMultiscaleTransform. Most relevant settings were 6 layers and small scale 8 (3) as scaling function. This creates way too much compression, so this image was blended into the original in a 50/50 balance using the Cosmicphotons ImageBlend script.
In the original processing I had used S0 Galaxy as the white balance reference in SPCC. It usually renders a bit cooler than Average Spiral Galaxy, which I prefer. This time however, the galaxy came out a bit blend. So I ran another SPCC using Average Spiral Galaxy as the reference. Originally this came out quite nice. But after stretching, where colour was preserved as much as possible, the galaxy had too much of a yellow/orang-ish colour. A super tiny amount of correction on the CIE b* channel brought out the blueish hues just a bit more, making the overall appearance much more balanced. To avoid the whole image being affected by this, a GAME mask was used to protect the rest of the image.
Remaining processing was done in a standard manner.
Processing workflow (click to enlarge)
This image has been published on Astrobin
