Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 5 · Portents, Comets
ग्रहचारः केतवश्च
तावन्मासैः फलं यच्छत्यष्टौ सारव्यवत्सरैः ।ये दिव्याः केतवस्तेऽपि शश्वज्जीवफलप्रदाः ॥ ९६ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 96.
it gives its result for as many months. (Our text is unclear here: a phrase read as 'eight years'.) The heavenly comets, too, always give results to living beings.
Simple meaning: A comet seen for some days gives results for that many months.
ह्रस्वः स्निग्धः सुप्रसन्नः श्वेतकेतुः सुवृष्टिकृत् ।
A short, bright white comet that soon fades brings good rain. A long one brings drought.
अनिष्टदो धूमकेतुः शक्रचापसमप्रभः ।
The smoke comet is bad and can bring harm to a kingdom.
मणिहारस्तुवर्णाभा दीप्तिमंतोऽर्कसूनवः ।
Bright gold-like comets born of the Sun, seen in the east or west, can bring loss to kings.