Hemisphere:  Southern  ·  Constellation: Eridanus (Eri)  ·  Contains:  NGC 1721  ·  NGC 1723  ·  NGC 1725  ·  NGC 1728  ·  NGC1721  ·  NGC1723  ·  NGC1725  ·  NGC1728
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Galaxy group in Eridanus, 


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Galaxy group in Eridanus

Imaging telescopes or lenses: Plane Wave Instruments CDK 12.5"

Imaging cameras: Finger Lakes Instruments Proline 16803

Mounts: AP900GTO

Guiding telescopes or lenses: Plane Wave Instruments CDK 12.5"

Guiding cameras: Starlight Xpress Lodestar guide camera

Software: PixInsight  ·  MaximDL

Filters: Astronomik L R G B Series II

Dates:Jan. 9, 2021

Frames: 40x600"

Integration: 6.7 hours

Avg. Moon age: 25.50 days

Avg. Moon phase: 17.27%

Astrometry.net job: 4166756

RA center: 4h 59' 34"

DEC center: -11° 4' 20"

Pixel scale: 1.451 arcsec/pixel

Orientation: 127.640 degrees

Field radius: 0.342 degrees

Resolution: 1200x1200

Locations: Wiruna Dark Sky Site, Ilford, NSW, Australia

Data source: Traveller


It is difficult to find much information on this cluster. The redshifts of 1723, 1725 and 1728 are all quite similar (0.01248, 0.01296 and 0.01255) corresponding to distances of 53-58 Mpc. NGC 1721 has a slightly greater redshift of 0.01501, corresponding to a distance of 64 Mpc. However, these galaxies do appear to be interacting, so the differences in redshift could be explained by local velocities within the group and may not be indicative of actual distance variation


Sky plot

Sky plot


Galaxy group in Eridanus, 



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Rarely Imaged Small DSOs