Tuesday, November 27, 2007

ASTRONOMY Q/A 8

1. In the navigational triangle, the angle at the elevated pole is the ? Meridian.

2. The navigational triangle uses parts of two systems of coordinates, one of which is the horizon system and the other is the ? Celestial equator system.

3. The navigational triangle uses parts of two systems of coordinates one of which is the celestial equator system, the other system is the ? Horizon system.

4. What great circle is always needed to form the astronomical triangle ? Celestial meridian.

5. The horizontal plane, perpendicular to the zenith ­nadir axis, that intersects with the celestial sphere and is tangent to the earth is called the ? Geoidal horizon.

6. What is NOT a side of the navigational triangle used in sight reduction ? Altitude.

7. A vertex of the navigational triangle is NOT located at the ? Coaltitude.

8. A correction for augmentation is included in the Nautical Almanac corrections for ?
The moon.

9. Apparent altitude is sextant altitude corrected for ? Inaccuracies in the reading and reference level.

10.When correcting the sextant altitude to apparent altitude you are correcting for inaccuracies in the reference level and ? For inaccuracies in the instrument.

11.The height of eye correction is smaller than geometrical dip because of ? Terrestrial refraction.

12.When applying a dip correction to the sighted sextant angle (hs), you always subtract the dip because you are correcting ? hs to the sensible horizon.

13. A semidiameter correction is applied to observations of ? The Moon.

14.The diameter of the Sun and Moon as seen from the Earth varies slightly but averages about ? 32'.

15. Where do you find the semidiameter correction to be used to correct sextant observations of the stars ? No semidiameter correction is used.

16.A phase correction is applied to observations of ? Planets.

17. A phase correction may be applicable to correct the sextant altitude correction of ? Some planets.

18. Because the actual center of some planets may differ from the observed center, the navigator applies a correction known as the ? Phase correction.

19.The phase correction should be applied to sights of Venus and Mars ? During twilight observations only.

20.What sextant correction corrects the apparent altitude to the equivalent reading at the center of the earth ? Parallax.