M72
NGC 6981
30’ x 20’ | 0.3”/px | 6000 × 4000 px | full resolution
Aquarius
RA 20h 53m 28s Dec -12° 32’ 14” | 0°
Messier 72 (also known as NGC 6981) is a globular cluster in the south west of the very mildly southern constellation of Aquarius. M72 was discovered by astronomer Pierre Méchain in 1780. His countryman Charles Messier looked for it 36 days later, and included it in his catalog. Both opted for the then-dominant of the competing terms for such objects, considering it a faint nebula rather than a cluster. With a larger instrument, astronomer John Herschel called it a bright "cluster of stars of a round figure". Astronomer Harlow Shapley noted a similarity to Messier 4 and 12. Based upon a 2011 census of variable stars, the cluster is 54.57 ± 1.17 kly away from the Sun. It has an estimated combined mass of 168,000 solar masses (M☉) and is around 9.5 billion years old. The core region has a density of stars that is radiating 2.26 times solar luminosity (L☉) per cubic parsec. There are 43 identified variable stars in the cluster.
source: Wikipedia
Data Acquisition
Data was collected over 11 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 12 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.
My experience with globular clusters is that sharpening in BlurXTerminator can best be set to “0” or a very low value, as artefacts can show up very quickly in the fabric behind the stars towards the nucleus of the cluster. That leaves some extra room for sharpening later on in the process. In this case a very mild sharpening was applied using UnsharpMask towards the end of the processing, just to give the slightest extra punch to the image. The rest was done by dialling in carefully brightness and contrast using the GHS tool.
The rest of the processing workflow followed regular procedures.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
