A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Navigator's Vision,Day or Night.
From: Byron Franklin
Date: 2009 Oct 11, 08:45 -0700
From: Byron Franklin
Date: 2009 Oct 11, 08:45 -0700
On Polaris Subs we had two periscopes one for general use and one type 11 to give azimuth bearing accuracy needed for the SINS while on surface, the general use was for Navigation and all other use. The orders were to proceed undetected; we never broke or surfaced during the 2.5 month. If we detected another ship we cleared away from the area. Once we went down, we had a huge area that we hid in. There was no reason for anyone to know where we were and each patrol was made with no thought but to remain undetected. 3 Sins were the main Navigation means but they were continued in check with one another and the personnel were well trained to monitor them. Any more would be top secret they may use the same procedures today? The Standard Navy Sextant was adequate for general Navigation �David White Company Mark II, 3 power, 10 degree true field. I did see other sextant�s with large lens and more power, outside the navy. On the SUB all navigation activity was in a Navigation Center down in the sub. I did use the periscope �SCAR GEAR,� that I remenber had a gyro input and printed out each shot. Analyzing Sextant Sights. I used SCAR GEAR on the SSBN Abraham Lincoln and a bubble sextant on a Liberty Hull. The Scar Gear is an artificial horizon in the periscope, much like the bubble sextant. In rough sea with both, the observed body moves violently across the cross hairs, making the Observation open to large random errors. The suggested practice is to use an average of many shots of each body to get one acceptable observation for each body or star. After some unacceptable use of the gear, I decide to try another approach to find the best raw shot from a large number of individual shots To find the Best shot among the many you need a reliable reference to judge the ever- changing time and elevation of each shot. You must reduce work of each sight to a simple, but easy way of elimination (random) and many shots to one best shot. I concluded that a better solution to the average would be to plot the individual shots on graph paper with a time line (at the bottom) and a slope that a body is traveling upon. This slope would be a systematic reliable reference line for each shot judgment. The time of the first shot would be the start of a 4 minuet time line and also time to compute Local Hour angle LHA for table entree for tabular altitude (tab Hc) of the body. The far base of the horizontal time line of four minutes would start with the LHA and end with LHA1+l, four minutes of time to arc, [one degree] or LHA297 and LHA298. At right angle to the time line would be the raw Hc tab. out of the tables, the bottom is LHA 297�s Hc 46 38.1, the right angle at the top would be 298�s Hc 47 17.1. This SLOPE (STAR TRACK) would be drawn from the left beginning of the time line (LHA297 Hc tab. to the top LHA 298Hc tab four minutes later. Once the graph is completed and each raw shot!Hs is plotted in terms of time and Hs height the Hc slope can be moved parallel to its self among the plotted Hs�s on the time line for best agreement. Each Hs shots should be easy to identify as systematic or random. A selection of one time and Hs shot can then be completed to height observed and to line of position for the fix. (If your Hs don�t match the Hc on the vertical, add or subtract an amount to fit, move the slope to select you best shot, than use the original Hs. The slope could be corrected for speed and direction during the four minutes traveled. In order to accommodate other star�s slopes, any time and Hs could be used to Finnish the sight and find the best shot. Best for a slow moving ship. On Oct 7, 10:26�am, Anabasi...---.com wrote: > This also works very well when trying to see running lights at a fair � > distance. �My use of this technique allows me to pick up ships at 15-20 nm �from > the bridge well before most of the other watch standers can see the �ship. � > Generally in good visibility, I can see the running lights soon �after they > pop over the horizon. > > Jeremy > > In a message dated 10/5/2009 2:21:55 P.M. Eastern Daylight Time, � > > byron...---.com writes: > > Navigator's vision at day and night. > The way you use �your eyes at night is different from the way you use them > during the day. With �normal day vision, you train your eyes to look > directly at the target. If you �catch something out of the corner of your eye, you > automatically move your �eyes to center on the target. Once you have done > so, you can see the target �clearly in color, and detail. In the dark, > however, instead of directing your �vision at the area you desire to see, you must > learn to use off-center vision �for a very dim light or star. �The first > step in training yourself in �night vision is finding a location free of normal > white city �lights, � Perhaps your backyard or better at sea. Wait until > your �eyes have adapted to the dark; this can take about 15 to 20 minutes. At > this �point the sky is black, some stars are bright, or some dim and you are > aware �of your surroundings. Your eyes are accustomed to the dark. If you > need a �light to read/write or see a star finder (NAVLIST 9471) use a red dim > light �only. �Look at the sky and find a bright star. Now slowly move your > eyes �until you see, or think you see, the dimmest star out of the corner of > your �eye. Look directly at the star. If it is a very dim star it will > "disappear" �when you look at it and won't reappear until you move your eyes and > "look" at �it using the off-center technique. It may well be fuzzy and lack > color. But �you do see it. What is happening here is that you are seeing it > with your �peripheral vision. Practice this off-center technique until you > are �comfortable picking up even the dimmest star. �Binoculars can help make > �some of the dimmer stars very bright. But other stars will disappear when > you �look directly at them, even with binoculars. At sea at night, relax and > move �your eyes slowly just a few degrees around the sky or the horizon. If > you �think you see a light, use the off-center vision technique to isolate > your �target. If the light is very faint and disappears, use a slow, > off-center eye �motion to pick it up again. Then use your binoculars to pick up any > color �details. Practice this off-center procedure until you are proficient > in seeing �things at night. When you are in the darkness, only a trained > eye can produce �the correct information quickly. In the day time when you > want that good �horizon for a star or planet before dark thickens the horizon > try the �"Vertical Sextant" NAVLIST of Sept 28. � --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To unsubscribe, email NavListemail@example.com -~----------~----~----~----~------~----~------~--~---