GUIDELINE FOR USING STAR CHART DIAGRAM
The diagram shows the evening sky as seen from latitudes 0 to 40 degrees North. The inner circle represents the horizon as seen from latitude 22.5 degrees North. The Star Chart has been extended on the northern and southern sides for use all over India. Beginners wanting to use the Star Chart should hold it overhead and turn it in such a way that the North, South, East and West marked on the Star Chart point to the correct directions. With some experience it would be possible to use it in a more convenient position. With the help of a few known star - groups in the sky the remaining stars can be easily identified using the above Star Chart. From a particular place these stars will be seen at about 2130 hrs. 2030 hrs. and 1930 hrs. of local mean time on the 1st, 16th and 30th of the month.
2.Local mean time for a particular place differs slightly from the Indian Standard Time (I.S.T.) by an amount equal to the difference ( 5h 30m - Longitude of place expressed in unit of time ). The following table gives the above correction for some important places in India :
3.The Star Chart meant for a particular day for a given hour can be used for the next day 4 minutes earlier and for the previous day 4 minutes later. For example, if a Star Chart is meant for 8-30 p.m. for the 16th, it can be used on the 17th at 8-26 p.m. and on the 15th at 8-34 p.m. In the same way it can be used for other months; for the 16th of previous month it will hold good at 10-30 p.m. and for the next month at 6-30 p.m. and so on.
4.The stars move from east to west in the sky in their daily motion ( due to rotation of the Earth ) at a rate of 15 degrees per hour. The Star Chart can also be used at other hours in the evenings after taking into account the above shift in position of the stars.