Star finder is used to choose suitable stars for celestial observations and for identifying stars.
Criteria for choosing the stars should be as follows-
- Angular separation should be as close as possible to 90°.
- Chosen stars magnitude should be low l.e. they should be bright.
- Altitude should be between 20°-70°.
- For morning twilight find out LMT Nautical Twilight and for evening twilight find out LMT Civil Twilight
- Apply LIT to get GMT and ZT to get SMT.
- Now apply run to last known position to get DR Latitude
- Longitude from current SMT to the SMT which obtained.
- Now from almanac get GHA Aries
- Apply longitude to get LHA Aries.
- From DR Latitude and LHA Aries go to star finder and using the correct template closest to DR Latitude choose 3-4 stars.
For identifying stars just get the azimuth of star and calculate LHA aries and latitude is known so use suitable template and put the pointer on LHA aries and using the azimuth find the star.