M48
M48 - Click here for full resolution
Messier 48, also known as NGC 2548, is a prominent open star cluster located in the constellation Hydra, the Water Snake. It was discovered by the French astronomer Charles Messier in 1771, though there was some initial confusion in its cataloging due to a recording error in its position. This error was later corrected, and M48 was properly identified. The cluster is situated approximately 1,500 light-years from Earth, making it one of the closer open clusters to our solar system. M48 spans about 23 light-years in diameter and contains roughly 80 stars, though some estimates suggest there could be up to 200 stars in the cluster. The stars in M48 are loosely bound by gravity, giving the cluster a somewhat scattered appearance. It is relatively young, with an estimated age of around 300 million years. The cluster is dominated by hot, blue-white main-sequence stars, which are characteristic of younger star clusters. However, it also includes a few evolved stars, such as red giants, which add to its diversity.
source: DeepSeek
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NGC2548
n.a.
Open Cluster
Hydra
08h 13m 43s
-05° 45.0′
1,500 ly
5.5
10 February
47º S
Conditions
M48 is best visible during Winter. Observed from the remote observatory at IC Astronomy in Oria , Spain, it reaches a maximum altitude of 47 degrees in early February. M48 as a stars-only object is a good ‘full moon’ target that is not too much effected by the light of the moon. M48 was photographed from the observatory in Spain over 4 nights during mid January 2025 when the moon was >75% illuminated.
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
M48 is a typical broadband object, that is not very critical to conditions of moon interference and was shot when moon illumination was >75%. With the moon being so prominent, all images, including the R,G and B images, were shot as 3 min exposures. The total exposure was 12 h. The field of view of this long focal length telescope was barely enough to capture the whole cluster. As can be seen from the annotated image below, the M48 boundaries are only just visible in the corners. Still most of the stars from the cluster have been captured in this image.
Resolution (original)
Focal length
Pixel size
Resolution
Field of View (original)
Rotation
Image center
9576 × 6388 px (61.2 MP)
2585 mm @ f/7.3
3.8 µm
0.30 arcsec/px
48' x 32'
-0.117°
RA: 08h 13m 39.434s
Dec: -05° 43’ 35.03”
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.
Stretching a stars only image can be a bit tricky. The various scripts and pixelmath formulas can wash out colour quickly. An arcsinh stretch retains colour much better, or alternatively one can use the Colour mode in GHS, rather than the RGB mode. The latter option was applied for the RGB channel of this image. The luminance was stretched using the Bill Blanshan script. Now it is important to make sure the Lum and RGB star sizes are about the same. In the original stretch, Lum came out with bigger stars than RGB. To compensate, the RGB was convoluted, to spread out the colour a bit, and the CosmicPhotons script Starreduction was used to reduce star size in Lum. The result was pretty well overlapping star sizes and matching Lum and RGB signals.
Remaining processing was done in a standard manner.
Processing workflow (click to enlarge)
This image has been published on Astrobin
