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» Online Classroom   » Celestial Navigation   » Public Discussion of Cel Nav   » Practical tips for taking sights underway

   
Author Topic: Practical tips for taking sights underway
Lehua-Kona


 - posted July 12, 2011 12:53 AM      Profile for Lehua-Kona           Edit/Delete Post 
Aloha,

I have completed the course and have been taking sights at the shoreline for awhile. Last week I completed a night crossing from Lahaina, Maui to Honolulu, Oahu and thought it would be a perfect opportunity to begin to take sites underway. I was able to plan and time nautical twilight/civil twilight with our estimated location in the channel correctly. We were pretty much where I thought we would be, between Oahu and Molokai with the wind just blustering and the seas exactly what I would have expected.

There is a short window from nautical twilight to civil twilight to sunrise at this latitude and I am having some trouble setting my IC error and getting in multiple sites before my window expires - meaning that it gets to light or too dark before I can complete my sites.

I seem to have trouble at the cusp of civil/nautical twilight especially when there are clouds on the horizon - and there are always clouds on the horizon. The clouds are so dark at this stage, I have trouble determining the horizon. And when it gets dark, it gets really dark.

This was highlighted during our crossing to Oahu, as by the time it was light enough to really confirm that I had the horizon, I only had twenty minutes left to get all of my sights in- which is just not enough for me at this point. I am still too slow and am still learning where to sit/stand, etc.

Are there any tips that you could suggest to assist me?

Mahalo,

From: Maui
David Burch


 - posted July 12, 2011 11:16 AM      Profile for David Burch           Edit/Delete Post 
The main note would be to do the IC work before the sights at night and after the sights in the morning so it does not use up your time.

Also precompute all the sights so they are quicker... much quicker.

then start with the sights that are in the direction of the darkest part of the horizon first. when precomputed, you can do these sights before they are visible to the naked eye.

and of course if you have venus or jupiter out bright you can do them early at night and late in the morning with clear horizon.

note these are not special instructions, but rather standard procedures outlined in our textbooks... ie we are just calling on the basics, which are just more important when you are near the tropics with short twilights.

From: Starpath, Seattle, WA


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