Conversation so far:
who built the jantar mantar observatories in jaipur and delhi
Maharaja Jai Singh II of Jaipur constructed five Jantar Mantar in total, in New Delhi, Jaipur, Ujjain, Mathura and Varanasi
when were the jantar mantar observatories completed
The Jantar Mantar observatories were completed between 1724 and 1735
what was the purpose of the jantar mantar observatories
The primary purpose of the Jantar Mantar observatory was to compile astronomical tables and to predict the times and movements of the sun, moon and planets
how many instruments are there in the jantar mantar observatory in jaipur
The Jantar Mantar observatory in Jaipur consists of nineteen instruments

Question: what are the instruments used for
Self-contained rewrite: what are the instruments in the jantar mantar in jaipur used for