I was just watching the Enemy Below with Robert Mitchum (my late father loved that movie) and I was wondering what the pillar outside the captain was using does. Took me 30 mins to figure it out, there’s not much info easy to find that describes the instruments on the bridge especially on wwii destroyers. Thank you for making such a video very well done.
Hi Mcgiiver, I was looking for some thing like this for my yacht . used one when I was on a small ship. not many yacht people would know about then or how to use then. or what about this TB=CC+RB i.e True Bearing =Course+Relative . What do you think about using Horizontal sextant angle ? Also would be great if you could show it on paper that is the working out
I honestly have not used a sextant in the horizontal position, so I really can't speak to that. The solutions on paper is a good idea, I am just not sure how to present it on UA-cam.
+Mcgiiver L Hi Mcgiver L. Thanks for your reply , a solution on how to do it on UA-cam is set up your camera as you have now and see the chart behind you put a big bit of paper on it and draw writer it on there . If I can see someone else doing it I will send it to you. Keep up the good work.
This is the narrative from the video. West Bank Fishing Trip, Using a Pelorus Two Bearing Fix On 30 May 2015, we depart Keyport Harbor, NJ, N40 26.2’, W74 12.5’ and proceed out the Keyport Harbor Channel until we reach the last channel buoy #1. We are using NOAA chart 12327. At that point we turn east to a course, 091 magnetic and head toward one of our familiar landmarks, the Keansburg #1 Buoy, about 2.7 Nm away. Passing the #1 bouy, we turn to course 063 mag and proceed on the long run toward West Bank Light. About 6 minutes later we desire to know our position at this time. At this point, we realize we left our handheld GPS back at the dock in our truck. However, we are prepared in that we have our chart, our pelorus, and a table of azimuths of the sun. So we decide to attempt to locate our present position using the two bearing method. We ask our helmsman to hold us on a steady course and tell us the compass bearing he is running. He calls out 063 magnetic. We set our pelorus compass card to 063 at the lubber line, lock the card, and bring it to a convenient place on deck that will let us align the body of the pelorus with the fore and aft centerline of the boat. We scan the horizon for two identifiable landmarks that appear on our chart. Ideally, the two landmarks should be separated by an angle of roughly 90 degrees. So we identify the east Tower of the Verrazano Narrows Bridge in NY off our port side. We also identify the Sandy Hook Lighthouse on our starboard side. Using the sighting vanes on the pelorus, keeping the unit aligned with the ship’s centerline, we take a bearing on the VZ bridge tower and get 35 degrees, which is a mag bearing, because we previously set the compass card on the pelorus to our ship’s mag course. We take a similar bearing on the Sandy Hook Lighthouse and get 126 degrees, also magnetic. As a check, we take a third bearing on the end of the Earle Ammunition pier and get a bearing of 145 degrees. We then proceed to plot our landmark sights on the NOAA chart. Based on this two bearing fix, we conclude that our position is N40 29.8’, W74 06.4’, about 2.8 Nm off Keansburg. Compass Check Using the Sun After several hours, of fishing at West Bank, we decide it is time to return to port, we head back. We see the sun dropping low in the sky and decide we can use the sun to make a check of our compass. The time is 19:30 local time. We set up the shadow pin on the pelorus, or raise the sight vanes, as the case may be, and align the unit with the ship’s centerline. We have previously looked up the azimuth of the sun for our particular point in time using one of numerous methods or apps, and find that at 19:30 hours on today’s date, the sun is at 292 degrees true. With the pelorus as level as possible, we observe the suns shadow on the pelorus card. We turn the pelorus card and locked sight vanes in unison, until the shadow is aligned with the sight vane arrow or index, with the reciprocal azimuth of the sun which is 292 minus 180 or 112 degrees and lock the card in place. Since the body of the pelorus is aligned parallel with the fore and aft centerline of the ship, we can read the ship’s course at the index mark or lubber line on the body of the pelorus; in this case it reads 239 degrees. You must note that this azimuth is a true azimuth to which we must add west declination (or subtract east) to get our magnetic azimuth. In this case we know the declination is 13 degrees west, for this approximate location, therefore our magnetic azimuth is 252. Since this is in agreement with our ship’s compass reading of 252 magnetic, we conclude that our ship’s compass is accurate enough for our needs on this course. Deviation sources on our ship may cause the compass to be inaccurate on other points of sail. Vessel Crossing Situation As we continue back toward our home port, having just passed Old Orchard Shoal Light, on a course of roughly 252 mag, we observe a vessel on our port side, running approximately northwest, in the Raritan Bay East Reach channel, that looks like it will cross our path. Remembering the rule of thumb, that if the bearing to a crossing vessel does not change, a collision will occur, we decide the prudent action would be to check using the pelorus. We set the compass card on the pelorus to zero, which corresponds to the centerline of our ship and the arbitrary direction the bow is pointed. We take a relative bearing of the crossing vessel and note it as 322 degrees. After a few minutes of running, we check the bearing again and still note 322 degrees. This means a collision is imminent unless action is taken. At this point we reduce our speed maintaining the same course. A few minutes later we again check the bearing to the vessel and notice that it has changed to 345 degrees. We continue and the vessel safely crosses our path ahead of us.
I was just watching the Enemy Below with Robert Mitchum (my late father loved that movie) and I was wondering what the pillar outside the captain was using does. Took me 30 mins to figure it out, there’s not much info easy to find that describes the instruments on the bridge especially on wwii destroyers. Thank you for making such a video very well done.
Hi Mcgiiver, I was looking for some thing like this for my yacht . used one when I was on a small ship. not many yacht people would know about then or how to use then. or what about this TB=CC+RB i.e True Bearing =Course+Relative . What do you think about using Horizontal sextant angle ? Also would be great if you could show it on paper that is the working out
I honestly have not used a sextant in the horizontal position, so I really can't speak to that. The solutions on paper is a good idea, I am just not sure how to present it on UA-cam.
+Mcgiiver L Hi Mcgiver L. Thanks for your reply , a solution on how to do it on UA-cam is set up your camera as you have now and see the chart behind you put a big bit of paper on it and draw writer it on there . If I can see someone else doing it I will send it to you. Keep up the good work.
This is the narrative from the video.
West Bank Fishing Trip, Using a Pelorus
Two Bearing Fix
On 30 May 2015, we depart Keyport Harbor, NJ, N40 26.2’,
W74 12.5’ and proceed out the Keyport Harbor Channel until we reach the last
channel buoy #1. We are using NOAA chart 12327. At that point we turn east to a course, 091 magnetic and head toward one of our familiar landmarks, the Keansburg #1 Buoy, about 2.7 Nm away. Passing the #1 bouy, we turn to course 063 mag and proceed on the long run toward West Bank Light.
About 6 minutes later we desire to know our position at this time. At this point, we realize we left our handheld GPS back at the dock in our truck. However, we are prepared in that we have our chart, our pelorus, and a table of azimuths of the sun. So we decide to attempt to locate our present position using the two bearing method.
We ask our helmsman to hold us on a steady course and tell us the compass bearing he is running. He calls out 063 magnetic. We set our pelorus compass card to 063 at the lubber line, lock the card, and bring it to a convenient place on deck that will let us align the body of the pelorus with the fore and aft centerline of the boat. We scan the horizon for two identifiable landmarks that appear on our chart. Ideally, the two landmarks should be separated by an angle of roughly 90 degrees.
So we identify the east Tower of the Verrazano Narrows Bridge in NY off our port side. We also identify the Sandy Hook Lighthouse on our starboard side. Using the sighting vanes on the pelorus, keeping the unit aligned with the ship’s centerline, we take a bearing on the VZ bridge tower and get 35 degrees, which is a mag bearing, because we previously set the compass card on the pelorus to our ship’s mag course. We take a similar bearing on the Sandy Hook Lighthouse and get 126 degrees, also magnetic. As a check, we take a third bearing on the end of the Earle Ammunition pier and get a bearing of 145 degrees.
We then proceed to plot our landmark sights on the NOAA
chart. Based on this two bearing fix, we conclude that our position is N40
29.8’, W74 06.4’, about 2.8 Nm off Keansburg.
Compass Check Using the Sun
After several hours, of fishing at West Bank, we decide it is time to return to port, we head back. We see the sun dropping low in the sky and decide we can use the sun to make a check of our compass. The time is 19:30 local time. We set up the shadow pin on the pelorus, or raise the sight vanes, as the case may be, and align the unit with the ship’s centerline. We have previously looked up the azimuth of the sun for our particular point in time using one of numerous methods or apps, and find that at 19:30 hours on today’s date, the sun is at 292 degrees true.
With the pelorus as level as possible, we observe the suns shadow on the pelorus card. We turn the pelorus card and locked sight vanes in unison, until the shadow is aligned with the sight vane arrow or index, with the reciprocal azimuth of the sun which is 292 minus 180 or 112 degrees and lock the card in place. Since the body of the pelorus is aligned parallel with the fore and aft centerline of the ship, we can read the ship’s course at the index mark or lubber line on the body of the pelorus; in this case it reads 239 degrees. You must note that this azimuth is a true azimuth to which we must add west declination (or subtract east) to get our magnetic azimuth. In this case we know the declination is 13 degrees west, for this approximate location, therefore our magnetic azimuth is 252. Since this is in agreement with our ship’s compass reading of 252 magnetic, we conclude that our ship’s compass is accurate enough for our needs on this course. Deviation sources on our ship may cause the compass to be inaccurate on other points of
sail.
Vessel Crossing Situation
As we continue back toward our home port, having just passed Old Orchard Shoal Light, on a course of roughly 252 mag, we observe a vessel on our port side, running approximately northwest, in the Raritan Bay East Reach channel, that looks like it will cross our path. Remembering the rule of thumb, that if the bearing to a crossing vessel does not change, a collision will occur, we decide the prudent action would be to check using the pelorus.
We set the compass card on the pelorus to zero, which corresponds to the
centerline of our ship and the arbitrary direction the bow is pointed. We take
a relative bearing of the crossing vessel and note it as 322 degrees. After a
few minutes of running, we check the bearing again and still note 322 degrees.
This means a collision is imminent unless action is taken. At this point we
reduce our speed maintaining the same course. A few minutes later we again
check the bearing to the vessel and notice that it has changed to 345 degrees.
We continue and the vessel safely crosses our path ahead of us.