Dog days sometimes used for the lethargic summer markets. Various computations of the dog days have placed their start anywhere from 3 July to 15 August and lasting for anywhere from 30 to 61 days. They may begin or end with the cosmical rising or heliacal rising of either Sirius in Canis Major or Procyon (the "Little Dog Star") in Canis Minor and vary by latitude, not even being visible throughout much of the Southern Hemisphere. Sirius observes a period of almost exactly 365¼ days between risings, keeping it largely consistent with the Julian but not the Gregorian calendar; nonetheless, its dates
Sirius indigenous Boorong people of northwestern Victoria named Sirius as "Warepil". In 1717, Edmond Halley discovered the proper motion of the hitherto presumed "fixed" stars after comparing contemporary astrometric measurements with those from the second century AD given in Ptolemy's "Almagest". The bright stars Aldebaran, Arcturus and Sirius were noted to have moved significantly; Sirius had progressed about 30 arc minutes (about the diameter of the Moon) to the southwest. In 1868, Sirius became the first star to have its velocity measured, the beginning of the study of celestial radial velocities. Sir William Huggins examined the spectrum of the star and