It was time to leave Horta, though in truth no one ever wants to leave Horta. The Azorean natives are so friendly and welcoming, the anchorage so secure, the bars so plentiful, why would anyone want to leave? Even Peter’s Sport Cafe, perhaps one of the most famous sailor bars in the western hemisphere, though by now, possibly overrated, overpriced and overcrowded, is still a comfort.
The little town is bursting at the seams with sailors and traffic. Faial, the island of which Horta is just a small part, is awash in blue hydrangeas and yellow and red nasturtiums. It’s a vertiginous volcanic outcrop in the middle of the Atlantic Ocean known for the skill of the native fishermen. Nineteenth century Faial was the first stop for many New Bedford whalers not just for provisions and water, but for boat steerers and harpooners as well.
Once clear of land I resume my celestial navigation observations, though my ability to get star sights is still hampered by my lack of practice. I concentrate instead on observations of the sun, obtaining sun lines, then advancing Lines of Position or establishing latitude by taking observations at Local Apparent Noon (LAN).
During this leg of the passage, the full moon was waning providing a perfect opportunity to take some lunar observations. In the first and third quarter of the moon cycle, the moon is visible during the day and can also be used with an observation of the sun for a moon-sun fix. During the first quarter the moon is visible in the afternoon, rising in the east. In the third quarter the moon is visible setting in the west.
Lunar observations are thought to be complicated and messy and once were, but dedicated Moon Tables have been developed removing much of the complicated math. These tables, appropriately called Altitude Correction Tables Moon, are not difficult, but if one is out of practice — as I was — they can initially be a little offsetting. Because I did an upper-limb observation, this caused some consternation because I had neglected to read the directions stating that 30 feet must be subtracted from the sight reduction if an upper-limb observation is taken for an LOP. I got it right the second time.
The procedure for reducing a lunar sight is to follow the daily entry procedures in the Nautical Almanac. The moon tables are the second column after the daily sun tables. As well as GHA, there is a v correction (always added to GHA), declination, d-correction, similar to the d-correction for the sun, and something called HP, which stands for horizontal parallax. It’s easy to make mistakes using this table, so stay focused. As with everything else, practice makes perfect.
So let’s do an observation of the moon on May 25th. The DR of Relentless is N 41° 52’ by W 13° 02’. The height of eye is 20 feet. There is no index error. The observation is taken at 06:25:20 GMT. It is an upper-limb shot. The HS is 14° 02.8’. n
What is the HO?
1. What is the intercept and bearing?
2. Plot.
For the answers go HERE.