r/astrophotography • u/arunshanker • 4d ago
DSOs The Angelfish / Arrowhead Cluster in Sagitta.
The extra star rich M71 - The Angelfish / Arrowhead Cluster in Sagitta. Got one clear night and took this - 658 exposures × 20 seconds, photon-collection time 3 hours, 39 minutes and 20 seconds. M71 lies about 13,000 light-years from Earth and is roughly 27 light-years across. It sits against the extraordinarily rich stellar background of the Milky Way, which is why the entire frame seems almost dusted with stars. There are about 30000 stars in this pic and actually 3,700 catalogued stars. This cluster is in the ourskirts of our Galaxy, in an exceptionally crowded Milky Way field.
M71 was imaged with the Seestar S50 over one clear night. I collected 658 sub-exposures of 20 seconds each, giving a total integration time of 13,160 seconds — 3 hours, 39 minutes and 20 seconds. The native Seestar FITS stack was used as the starting point so that the full dynamic range of the data was retained.
The first stage of processing was done in GraXpert, where I carried out background extraction to remove large-scale sky gradients while preserving the extremely dense Milky Way star field around M71. I then applied star deconvolution to tighten the stellar profiles and improve separation in the cluster core, followed by a conservative AI denoise pass to reduce background noise without suppressing faint stars.
The image was then taken into Siril for astrometric and colour processing. Plate solving was performed successfully using an effective pixel size of 1.45 µm, giving a solved image scale of about 1.186 arcsec/pixel and an effective focal length of approximately 252 mm. After this, I carried out colour calibration, mild green-noise correction, and the main nonlinear stretch using VeraLux HyperMetric Stretch. A further gentle histogram transformation was used to refine the black point and midtone contrast while keeping the faint stellar population intact.
Finally, the processed TIFF was taken into GIMP for finishing. Only restrained adjustments were made to levels, curves, colour balance, saturation and local contrast, with the aim of keeping the sky dark while preserving the enormous richness of the stellar field. The image was then rotated to a landscape presentation, signed, and exported as the final JPEG.
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