Who can do?

It is natural for an average person to get the doubt who are eligible to do Saṃdhyopāsana. The answer is simple. Everyone can do without any objection. This book emphasizes the same. In śabda kalpadrumaṃ (शब्दकल्पद्रुम) there is a mention of mantra updadeshams of Gayatri, Savitri and others, mauṃjī (the sacred thread worn by boys at the time of upanayanam) baṃdhanaṃ, and similar reforms/cultures which were also preached to women as saṃdhyāṃgas in the past as mentioned below –

स्त्रीशूद्रादीनां वैदिक्याः स्थाने तांत्रिकी संध्या उपदिष्टा स्त्रीणामपि संध्याधिकारः स्मर्यते वाल्मीकिना
strIshUdrAdInAM vaidikyAH sthAne tAMtrikI saMdhyA upadiShTA strINAmapi saMdhyAdhikAraH smaryate vAlmIkinA-

संध्याकालमनाः श्यामा ध्रुवमेष्यति जानकी।
नदीं चेमां शुभजलां संध्यार्थे वरवर्णिनी॥

saMdhyAkAlamanAH shyAmA dhruvameShyati jAnakI|
nadIM chemAM shubhajalAM saMdhyArthe varavarNinI||

Tāṃtrik Saṃdhyopāsana worship was instructed to women and śūdrās instead of Vedic Saṃdhyopāsana. One should not mistaken it for occult worship.

Valmiki Maharishi prescribed these types of worship for them as mentioned clearly in the sacred scripture Ramayan.

This was illustrated by Hanuman’s thoughts when he saw waters in a sacred river while searching for Mother Jaanaki in Lanka, “I shall wait here since Maa Sita would definitely come to this sacred river for Saṃdhyopāsana”.