Rishi: Unspecified in the provided excerpt; traditionally to be determined from the Anukramaṇī for VS 3.16.
Devata: Implicitly a luminous/solar or rite-essence deity (tejas/rasa-bandhu); exact devatā to be fixed by Anukramaṇī.
Chandas: Not determinable with certainty from the excerpt alone; requires metrical verification against the full pada count and accentual tradition.
Samhita Patha (Devanagari)अ॒स्य प्र॒त्नामनु॒ द्युत॑ᳪशु॒क्रं दु॑दुह्रे॒ अह्र॑यः । पय॑: सहस्र॒सामृषि॑म्
Transliterationásya pratnā́m ánu dyútáṃ śúkraṃ duduhre áhrayaḥ | páyaḥ sahasra-sā́m ṛ́ṣim
Translationഇവന്റെ പ്രാചീന പാതയെ അനുഗമിച്ച് അഹ്രയഃ (അവിശ്രാന്ത ശക്തികൾ) ശുക്രം—പ്രകാശമുള്ള, ശുദ്ധ ദ്യുതിയെ പിഴിഞ്ഞെടുത്തു; പയഃ—സഹസ്ര സാമങ്ങളുടെ ഋഷിയെപ്പോലെയും (ദിവ്യ) ക്ഷീരത്തെ.
Padapatha (Word Analysis)अस्य । प्रत्नाम् । अनु । द्युतम् । शुक्रम् । दुदुह्रे । अह्रयः । पयः । सहस्र-साम् । ऋषिम् ।
Word by Wordप्रत्नाम्the ancient (one/stream) द्युतम्splendour, shining light दुदुह्रेthey milked/drew out पयःmilk; nourishing fluid सहस्रसाम्(the ancient one) of a thousand sāman(-songs) 
Entities MentionedS
Sūrya/Āditya (luminous principle)Ṛ
Ṛṣi / Vāc (seerly speech) Viniyoga (Ritual Application)