After a hiatus of almost a year, I resumed astrophotography with great pleasure last friday night, with two targets : M92 and M51 (still in processing).
Both were shot using the RC8 with the Canon EOS Ra, with the 'new' feature of the ASIAIR Pro : the "Plan" mode, which allows you to sleep well while he does all the work... :-)
Things were set-up a bit in an unplanned manner, and I forgot the correct distance between the TS Optics field flattener and the sensor, as well as how to tweak my mirrors to get better stars... so there is a bit of coma and I need to adjust that next time.
Anyway, about M92 : this cluster is very old - ~ 11 billion years - made of low metallicity stars (which is logic given its age, as heavier atoms are produced and released during the death of stars).
It is "orbiting" the Milky Way above (or below...) the galactic plane : ~ 16 000 light years above and ~ 33 000 light years far from the galactic center (and ~ 26 700 ly far from earth).
It seems it is losing stars as it orbits the Milky Way, shredded by the gravitational forces of the galaxy compared to the weaker forces of the cluster itself. Its total weight is ~ 300 000 solar masses (which gives a rough idea of the number of stars in the cluster....), and its "trail" of stars could be 10% of that.
This trail could have been formed 500 millions years (recently then) and it seems astronomers are still wondering what happened as it happened suddenly (otherwise, it would have lost all its mass by then).
I put links to a nice article about it, and a nice image from ESA that shows its position :
https://www.cfht.hawaii.edu/en/news/CFISM92/https://arxiv.org/abs/2009.04487
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