If on all the other days Surya Namaskara practices are done regularly, then Chandra Namaskara is done on days like Amavasya and poornima.
Chandra Sadhana is Dhrti’s Value added service. A sadhana from Tantra yoga for the welfare of yoga sadhakas done on days like Full Moon and No moon, when the lunar energy is high. Practices like Chandra Namaskara with mantras, Yoga Nidra, and Jyoti trataka are performed. Thus balancing the two energies, Ida and Pingala which is the Aim of Hatha yoga