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After sending out the Antares-Rho-Mars Pentagon image, a question was asked “Is that the globular cluster M80 at the top right?? If so, why doesn’t it look like a globular cluster??”
The answer: Yes – that is M80. And it isn’t poorly processed. There is a relatively unique feature of M80 that all but defies resolving the central hub stars. A perusal of many M80 images taken with widefield scopes and even long focal length scopes (links below) show an overexposed unresolved “blocked-up” central hub in almost all cases. Tony Hallas did the best job preserving that tight hub of central stars in any widefield image I could find! In many images, M80 looks like a fuzzy star. Reason: M80 has one of the densest nuclei of all 147 known Milky Way globular clusters! So I decided to violate it with some focal length, namely the 14.5-inch RCOS, to see if I could tame the hub and generate an image akin to a globular. The resulting 20 minute LRGB is an insert in the upper left of my cropped Rho image (without Mars). I couldn’t tame the brilliant nucleus in CCDStack using DDP techniques. I needed Tony Hallas’ magic wand taming whip to subdue and control the bright center! Notice that the Hubble Space Telescope image (first link below) has white-clipped blocked up nucleus!!! Good luck finding quality images of M80 by amateurs with central resolution!
P.S. – How many of you remember the Classification of Globular Clusters in Burnham’s Celestial Handbook, (Vol. 1, page 101) where globs where classed from I (extremely rich and highly compressed) to XII (loose)??? M80 would certainly be a class I. Vol. 3 has a quote from Sir William Herschel (1785) referring to M80 as “the richest and most condensed mass of stars which the firmament can offer to the contemplation of the astronomer”. Agreed!
http://apod.nasa.gov/apod/ap990707.html — Hubble M80 image – gorgeous but “blocked up” nucleus!
http://apod.nasa.gov/apod/image/0607/RhomosaicM_mmg_f.jpg – nice Rohm by Gendler – see M80 at upper right
http://www.pampaskies.com/gallery3/Wide-Field/rho-final — nice Rho from Argentina – M80 is a fuzzy “star”
http://apod.nasa.gov/apod/ap150706.html — nice Rho from Germany – poor M80
http://www.astrophoto.com/images/RhoO.jpg — Tony Hallas Rho — as good as widefield M80 (upper right) could be