Cel Nav Flashcards
1
Q
What is the ideal observation period for star sights?
A
Halfway from sunrise or sunset to Civil Twilight and hallway from Civil Twilight to Nautical Twilight
2
Q
Criteria to consider for star selection
A
- Body must be visible (could be obscured by clouds)
- Horizon must be clear to measure the altitude (could be obscured by background light or weather or not attainable because of flat calm sea)
- minimum 3 stars, ideally 4 or more to obtain reliable fix
- With 3 stars, ideal angle of cut is 120°
- With 4 stars we can compensate for random errors (due to atmospherics or quality of horizon)
- 4 stars, choose pairs of opposite stars, one in each quadrant. Gives square cocked hat, we are in the middle, high level or reliability.
- Additional stars on N/S or E/W plane to cross through middle of cocked hat
3
Q
What is the correct order for taking observations?
A
- From East to West, due to visibility of stars and horizon.
- NE and SE first, NW and SW second
