Yes Rishi Dirghatamas can be considered as one of the vedic astrologer .
According to vedic scholar David Frawley in the Rig Veda, there are clear references to a chakra or wheel of 360 spokes placed in the sky. The number 360 and its related numbers like 12, 24, 36, 48, 60, 72, 108, 432 and 720 occur commonly in Vedic symbolism. We find clear reference of zodiac in the hymns of Rishi Dirghatamas (RV I.140 – 164) . Much of this hymn can be understood as a description of the zodiac. It begins: the hymns of Dirghatamas speak clearly of a zodiac of 360 degrees, divided in various ways, including by three, six and twelve, as well as related numbers of five and seven.
Dirghatamas is one of the most famous Rig Vedic Rishis. He was the reputed purohit or chief priest of King Bharata (Aitareya Brahmana VIII.23), one of the earliest kings of the land, from which India as Bharata (the traditional name of the country) was named. Dirghatamas was one of the Angirasa Rishis, the oldest of the Rishi families, and regarded as brother to the Rishi Bharadvaja, who is the seer of the sixth book of the Rig Veda. Dirghatamas is also the chief predecessor of the Gotama family.
Here are the mantras from Rig-Veda 1.164 .
And here is English
द्वादशारं नहि तज्जराय वर्वर्ति चक्रं परि दयामृतस्य |
अग्ने मिथुनासो अत्र सप्त शतानि विंशतिश्च तस्थुः || 11||
dvādaśāraṃ nahi tajjarāya varvarti cakraṃ pari dyāṃ ṛtasya |
putrā aghne mithunāso atra sapta śatāni viṃśatiśca tasthuḥ ||
11 Formed with twelve spokes, by length of time, unweakened, rolls
round the heaven this wheel of during Order. Herein established,
joined in pairs together, seven hundred Sons and twenty stand, O Agni.
दवादश प्रधयश्चक्रमेकं त्रिणि नभ्यानि क उ तच्चिकेत |
साकं त्रिशता न शङकवोSर्पिताः षष्टिर्न चलाचलासः ||48||
dvādaśa pradhayaścakramekaṃ trīṇi nabhyāni ka u tacciketa |
tasmin sākaṃ triśatā na śaṅkavo.arpitāḥ ṣaṣṭirna calācalāsaḥ ||48||
48 Twelve are the fellies, and the wheel is single; three are the
naves. What man hath understood it? Therein are set together spokes
three hundred and sixty, which in nowise can be loosened.
As the topic of Zodiac is related astrology and from above conclusion of scholors we can say that Rishi Dirghatamas was a rig-Vedic astrologer .