Greetings of the day from Siddhivinayak Solutionss!!
Sign is called as Rashi (Zodiac) so it is 12 in numbers they are- Mesha, Vrushabha, Mithuna, Karka, Simha, Kanya, Tula, Vrischika, Dhanu, Makara, Kumbha and meena
Where as Constellation is called as Nakshatras and there are 27 nakshatras (If counted Abhijit Nakshatra) then 28 Nakshatras
they are Ashvini, Bharani, Krittika, Rohini, Mrigashirsha, Ardra, Punarvasu, Pushya, Ashlesha, Magha, Purva Phalguni, Uttara Phalguni, Hasta, Chitra, Swati, Vishakha, Anuradha, Jyeshtha, Mula, Purva Ashadha, Uttara Ashadha, Shravana, Dhanishtha Shatabhisha, Purva Bhadrapada, Uttara Bhadrapada, and Revati