List of comets with no meaningful orbit
Here is the list of comets designated with X/ prefix. The majority of these comets were discovered before the invention of the telescope in 1610, and as such there was nobody to plot the positions of the comets to a high enough precision to generate any meaningful orbit. Later comets, observed in the 17th century or later, either did not have enough observations, sometimes as few as one or two, or the comet disintegrated or moved out of a favorable location in the sky before it was possible to make more observations of it.
|X/1954 C2||Weinberger & Auner / Palomar DSS|
|X/1954 V2||Meyer/Palomar DSS|
|X/1955 G2||Auner & Dengel & Weinberger / Palomar DSS|
|X/1976 U2||Eberst & Coulson & Tritton|
|X/1978 W1||West & Schuster|
|X/1987 A2||McNaught & Hartley|