Rudra's Nakshatra Is Ardra, in Mithuna

Mithuna contains Mrigashira's later part, the whole of Ardra, and Punarvasu's opening. Only Ardra has Rudra as deity. Mrigashira's deity is Soma, the Moon, which is the other Shiva-adjacent star, the gentle one. A Mithuna Moon is not automatically Ardra. A Mesha or Karka Moon is not barred from Monday worship. The columns that rank rashis as Shiva's favorites are devotional marketing. The nakshatra list is specific. Rahu rules Ardra, so a Moon there can open life under Rahu's balance, eighteen years at full length if the star is fresh. That is a dasha fact beside the deity, not a prize for the sign Gemini.

Monday vrata follows the Moon, the ornament, more than it follows Ardra. A strong Moon supports the mind that keeps the vow. A Moon under Sade Sati can make the vow feel heavy for about seven and a half years without making Shiva angry in any chart sense. Rudraksha, the seed tied to Shiva's tear in the story, is matched by mukhi to a graha when the aim is remedial, and to simple devotion when the aim is only Shiva. Five mukhi, the Jupiter bead, is the common one. It is not reserved for Dhanu and Meena rashis, even though those signs belong to Jupiter. Worship is wider than the rashi table. The table people want is smaller than the worship.

Look at the Moon's sign and phase, and look at whether the Moon or the lagna falls in Ardra. Jyothish SI will show both with Lahiri ayanamsa. If neither is Ardra, you may still keep Monday. You do not need a favorite-rashi certificate. If the Moon is in Ardra, Rahu's house in the chart is the other fact worth reading, because the star's lord and the node's house are different. The dearness in the headline is Ardra's deity and the Moon's place in the icon. It is not a ranking of the twelve signs.