foreign [Music] in the previous video we had a quick introduction to the fact that ancient Indians have thought about very many different instruments astronomical instruments which are required for estimating certain Keen you know numbers and positional accuracy of the dominaries planets etc etc in this video we will look at a few of them just to get a sense of what these instruments are so we will start with the first instrument which is called a shanku and shanku is nothing but trade vertical stick which is a pointer tip it's called Naman in astronomy and this is required for setting the cardinal direction the starting point of any astronomical computation observation is setting the cardinal direction we should know which is east and which is West and so on otherwise what astronomy are you going to do so this instrument is for that so let us see how it works we place the Naman Ox this is the Naman exactly vertical on level ground so that at its tip X points to the Zenith so the axis pointing to the Zenith that is the first thing then we draw a circle with a suitable radius with the base of the gramman you know so this is the circle that we are talking about o as the center we draw a circle of a certain radius we Mark the points W Dash and E Dash you have the W Dash and E Dash here where the tips of the shadow of the demand are on the circle in the four known and the afternoon respectively So You observe that and then you know Mark these two points then these These are actually the eastwest Direction because the Shadows of the same length would be symmetrically situated with respect to the north south line so this is a simple shanku which can be used to set the cardinal direction so that is what this instrument is all about then we have the second instrument is a large wooden circular disk as you see here with an axis at the center this is the axis which is mounted there it is divided into 60 ghaticas and also into 12 signs of the ecliptic so you have the Aries you have the Taurus you have the Gemini cancer Leo Virgo Etc all the toll will have been here okay corresponding to the period of the risings in the place of observation because this can vary from place to place so it is in the period of place of observation the disc is rotated around the axis so that the shadow of the axis falls on the mark made for the position of the sun at Sunrise so basically by moving it that far so we have now ah moved this far let us say and that's where the shadow is falling so that says what exactly is a lagna because you know the sun has moved that far from the beginning you know that's what it mean number of gates will be seen between the point of Sunrise to the position of the Shadow which will also indicate the lagna that in this example that is how it is so an RD Walia is used for this purpose this is a simple representation of a chakra yantra chakrantra is made in the form of a plate of metal or seasoned wood and a needle is placed at the center that you see here when the instrument is illuminated by the Rays of the sun on both sides the shadow of the needle gives the angular height of the Sun so for his observatories at Jaipur and Varanasi Raja savai Jai Singh build chakra inras which are very large instruments they are mounted on pillars and fixed so as to revolve around the axis parallel to the Earth's axis so the axis carries a pointer which indicates a hover angle on the fixed Circle so you know it's mounted here as you see here and you know that's how we are able to use this chakra yantra I just now made a mention of Raja Jai Singh sawai he built what is called Jantar mantar the efforts of Raja Jai Singh savai who lived between 1686 and 1743 CE of he lived in Jaipur Mark a very significant milestone in the history of Indian astronomy because European instruments were not large and suffered from errors so Raja Jay Singh felt the need for making gigantic instruments really gigantic instruments that are sturdy free from wear and tear and not affected by changing weather conditions etc etc because you know all these changes may make the observations inaccurate which is what we felt so he really built a large such instruments so he took a different approach to build astronomical instruments and created a versatile astronomical Observatory by setting up a group of essential instruments in one place in they were a large instruments built physically and kept so that so many of them so it is like an enclosure you know if you go to Delhi we see the Jantar Mantra Jantar mantras were built in five places Delhi Jaipur Varanasi ujjain and mathura during his regime but unfortunately I think the others are all gone in bad condition I think so what I show here is one picture I would urge you to actually you know go through the internet there are videos there are articles to understand what has been the great contribution how some of the instruments that we talked about are being built there in gigantic scale so this is one side of actually anthra Raja the king of the instruments ah so which is used to measure whatever we have discussed I would urge you to go and see Jantar Mantra in Delhi either physically and understand what kind of an astronomical prowess that we have built and he has used Romani and other ideas and some of the western ideas also to put up all these Jantar mantas I think with this we will close this section on astronomy just to recapitulate Indians have had a very long Legacy of astronomy we have Vedic references we have the notion of month year adjustment between lunar and solar calendar written in Vedas we have vedank jyotisha which does approximate calculations then comes aryabhatia and the siddhanta period where there is formal mathematics with which we are able to strengthen our astronomical calculations model predictions you have nilakanta Somaya ji in 1500 CE who made Corrections and so on then we have all these Indian components leading to a panchanga which we use in our day-to-day basis which are all based on scientific principles and calculations which we in a very rudimentary way we saw it and of course a suite of instruments which are very important because astronomy is an observational science with this we'll close down this discussion on astronomy thank you [Music] thank you