Messier 5, M5, NGC 5904 Serpens
M5 was first documented by Gottfried Kirch and his wife Maria in 1702, then rediscovered by Messier in 1764 who thought it to be a nebula. It was first resolved into stars by Herschel in 1791. With integrated apparent magnitude of 6.0, it is easily identified with binoculars, but a 5-8 inch telescope is required to begin to identify individual stars, the brightest of which are of magnitude 12.2. The cluster is composed of 100 to 500 thousand members, distributed over 20 arcmin in angular size, or 165 LY in diameter. At least 105 members are known to be variable. Most of them are short term RR Lyrae type or "cluster variable stars". M5 is located at the approximate distance of .24,500 LY, and is thought to be between 10.5 and 13 billion years old.
When the photons captured in this image left the cluster, humans just began forming permanent settlements with cottages built of stone and mammoth bones. From the photons' perspective, travelling at the speed of light, time did not pass at all, and the journey was instantaneous.
The attached image was taken with a TSAPO100Q telescope, Sigma APO 1.4x tele-extender, Celestron AVX mount, Canon 600D camera, Astronomik CLS-CCD filter, and Orion 60mm F4 SSAGpro autoguider. The CLS-CCD filter blocks UV, violet, and deep blue light, resulting in markedly reduced Rayleigh scatter, smaller star size, and improved resolution in globular clusters.
This reprocessed image is a stack of 5 x 240 sec exposures at iso 1600, 65F, processed with 30 dark and 30 bias frames, 2x drizzle, 25% crop. Limiting magnitude is better than 17.
Software:used was PHD2, DSS, XnView, StarTools, and Neat Image.
Thank you for looking. Comments welcome.