In late June there was a very favourable flyby of the Potentially Hazardous Asteroid (152637) 1997 NC1.

Amateurs and professionals observed it from early May when it was an almost stationary mag 19 object in Cas. At closest approach on June 27 this ~1 km diameter body was 6.7 lunar distances from Earth and at mag 10, diving SW through Oph at 43 arcsec/minute. Sky conditions and holidays restricted my observations to June 20-27.

Its orbit was well defined and it's interesting to compare results from different 'families' of observers. I downloaded all observations submitted to the MPC and used Bill Gray's Find_Orb to produce the attached plots of residuals in RA and Dec. Most datapoints in the photometry plot are G mag, some V mag and very few R mag.

Unistellar is a range of smartscopes; 41 cm is 16-inch amateur 'ceiling'; ATLAS is a network of NASA survey scopes; Z92 is my setup.

MPC requires astrometry with a consistency of <1 arcsec. There's a lot of scatter in Unistellar astrometry (and from some larger scopes) otherwise their photometry is good.

For BAA time-series photometry of 1997 NC1 see the ARPS forum

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