I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 120 seconds each, obtained remotely on 2017, May 29.4 from Q62 (iTelescope network) through 0.43-m f/6.8 reflector + CCD, shows that this object is a comet with a diffuse coma nearly 10 arcsec in diameter.
M.P.E.C. 2017-L04 assigns the following preliminary parabolic orbital elements to comet C/2017 K4 (ATLAS): T 2018 Jan. 13.3; e= 1.0; Peri. = 20.42; q = 2.54; Incl.= 17.19
by Ernesto Guido