M25
IC 4725
48’ x 32’ | 0.3”/px | 9576 × 6388 px | full resolution
Sagittarius
RA 18h 31m Dec -19° 07’ | 180°
Messier 25, also known as IC 4725, is an open cluster of stars in the southern constellation of Sagittarius. The first recorded observation of this cluster was made by Philippe Loys de Chéseaux in 1745 and it was included in Charles Messier's list of nebulous objects in 1764. The cluster is located near some obscuring features, with a dark lane passing near the center. M25 is at a distance of about 2,000 light-years away from Earth and is 67.6 million years old. The spatial dimension of this cluster is about 13 light-years across. It has an estimated mass of 1,937 M☉, of which about 24% is interstellar matter. A Delta Cephei type variable star designated U Sagittarii is a member of this cluster, as are two red giants, one of which is a binary system.
source: Wikipedia
Data Acquisition
Data was collected over 6 nights in August and September 2025, mostly under full moon conditions, 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 7 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.
After gradient removal and colour calibration there were still colour casts in some areas of the background. Apparently the gradient correction was not 100% successful. The images were shot under near full moon conditions, which often gives difficult to manage gradients. To repair, a masked desaturation of only the background and removal of any residual green using SCNR was used to eliminate these remnants of colour gradients.
The rest of the processing workflow followed regular procedures.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
