A comet consists of a head or coma and a tail or tails as shown in this figure . The position angle or pa of the tail is measured from north through east, using the RA and dec co-ordinate system. The coma will show a degree of condensation or DC , and a very small number of bright comets may show hoods and other features such as jets. However the most important information is the total magnitude.
A comet that is low in the sky has to be brighter before you can see it. This graph shows an approximate limit.