Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 5 · Portents, Comets
ग्रहचारः केतवश्च
वरणधातुरर्केन्दू तुदते सर्वपर्वणि ।विक्षेपावनतेर्वंगाद्राहुर्दूरगतस्तयोः ॥ ८० ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 80.
By a boon, Rahu troubles the Sun and the Moon at every parva (junction day). Because of latitude and parallax, Rahu is sometimes far from them.
Simple meaning: Rahu troubles the Sun and Moon at new and full moons, but at times is too far to eclipse them.
षण्मासवृद्ध्या ग्रहणं शोधयेद्रविचंद्रयोः ।
Eclipses of the Sun and Moon are found six months apart. Seven gods rule the eclipse seasons in turn.
ब्रह्मेन्द्विंद्रधनाधीशवरुणाग्नियमाह्वयाः ।
A junction day ruled by Brahma brings growth to animals, crops and the twice-born.
तद्वदेव फलं सौम्ये श्लेष्मपीडा च पर्वणि ।
A junction day of Soma gives much the same, with phlegm trouble. Indra's may bring quarrels and crop loss.