M28
NGC 6626
22’ x 15’ | 0.3”/px | 4500 × 3000 px | full resolution
Sagittarius
RA 18h 24m Dec -24° 52’ | 0°
Messier 28, also known as NGC 6626, is a globular cluster of stars in the center-west of Sagittarius. It was discovered by Charles Messier in 1764. He briefly described it as a "nebula containing no star... round, seen with difficulty in 31⁄2-foot telescope; Diam 2′." It is about 18,300 light-years away from Earth. It is about 551000 M☉ and its metallicity (averaging −1.32 or 10 times less than our own sun), coherency and preponderence of older stellar evolution objects, support its dating to very roughly 12 billion years old. 18 RR Lyrae type variable stars have been found within. It bore the first discovery of a millisecond pulsar in a globular cluster – PSR B1821–24. This was using the Lovell Telescope at Jodrell Bank Observatory, England. A total of 11 further of these have since been detected in it with the telescope at Green Bank Observatory, West Virginia. As of 2011, these number the third-most in a cluster tied to the Milky Way, following Terzan 5 and 47 Tucanae.
source: Wikipedia
Data Acquisition
Data was collected over 8 nights in July and August 2025, using a 14” reflector telescope with full-frame camera at the remote observatory in Spain. Data was gathered using standard RGB filters. A total of approximately 10 hours of data was finally combined to create the final image.
Location Remote hosting facility IC Astronomy in Oria, Spain (37°N 2°W)
Sessions
Frames
Equipment
Telescope
Mount
Camera
Filters
Guiding
Accessoires
Software
Planewave CDK14 (2563mm @ f/7.2), Optec Gemini Rotating focuser
10Micron GM2000HPS, custom pier
Moravian C3-61000 Pro (full frame), cooled to -10 ºC
Chroma 2” RGB unmounted, Moravian filterwheel L, 7-position
Unguided
Compulab Tensor I-22, Dragonfly, Pegasus Ultimate Powerbox v2
Voyager Advanced, Viking, Mountwizzard4, Astroplanner, PixInsight 1.9.3
Processing
All processing was done in Pixsinsight unless stated otherwise. Default features were enhanced using scripts and tools from RC-Astro, SetiAstro, GraXpert, CosmicPhotons and others. Images were calibrated using 50 Darks, 50 Flats, and 50 Flat-Darks, registered and integrated using WeightedBatchPreProcessing (WBPP). The processing workflow diagram below outlines the steps taken to create the final image.
M28 is not a very large cluster, so the final image was cropped to approximately half the size in each dimension to have a nicely balance composition in the final image.
The rest of the processing workflow followed regular procedures.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
