M4 is a globular cluster visible in dark skies about one degree west of the bright star Antares in the constellation Scorpius. M4 is perhaps the closest globular cluster at 7000 light years, meaning that we see M4 only as it was 7000 years ago, near the dawn of recorded human history. Although containing hundreds of thousands of stars and spanning over 50 light-years, M4 is one of the smallest and sparsest globular clusters known. A particularly unusual aspect for a globular cluster is M4’s central bar of stars. M4 is one of the oldest objects for which astronomers can estimate age directly. Cluster white dwarfs appear to be at least nine billion years old – so ancient they limit the youth of our entire universe.

In 2021, I took this image over 4.7 hours (Luminance – 31 of 5 minutes and each color 15 of 3 minutes) using AG Optical 10″ 1650mm telescope.

In 2023, I used the Stellarvue SV130 f/6.6 of focal length 680mm to take a wider view and to include NGC 6144, another globular cluster, that appears in bottom right. But, this meant that the picture field of view was too close to Antares, which is one of the brightest stars in the night sky, so I got this big artifact from the rays of that star. You can also see some reflection nebulosity that is due to Antares lighting up passing nebula.

I took this image with 13 Luminance of 10 minutes each and 11 images each of the RGB colors of 5 minutes each, totaling to 285 minutes (almost 5 hours).