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Post by Sicilianhunter on Sept 11, 2019 21:24:34 GMT -7
I've had my eyes on one of these devices for quite some time and decided I need it as a part of my trekking kit. However, being the Noob that I still am, I know little about them and their applications. Can anyone enlighten me?
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Keith
City-dweller
Bushfire close but safe now. Getting some good rain.
Posts: 990
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Post by Keith on Sept 11, 2019 23:58:49 GMT -7
I've had my eyes on one of these devices for quite some time and decided I need it as a part of my trekking kit. However, being the Noob that I still am, I know little about them and their applications. Can anyone enlighten me? Mate I got mine because it was the least expensive on the market at the time. I can tell direction without a compass at sunrise & by the stars at night, & I can keep a straight line without a compass, but using a compass to maintain direction in all weather conditions is far easier. I have never used the sundial, I can tell the time well enough without it. Besides which it is calibrated for the Northern hemisphere. Keith.
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Post by spence on Sept 12, 2019 7:39:16 GMT -7
They aren't very complicated. They also only give you an approximation of the time, but close enough for our purposes.
Set the compass down on a level surface in direct sunlight.
Elevate the sundial pointer.
Rotate the compass so that the pointer is aligned with the north pointing needle.
The shadow of the pointer will fall on the time dial at local sun time.
Since magnetic north, where the compass needle points, and true north, the geographic north pole, aren't in the same spot, there is an error built into the operation of any magnetic compass. It's called magnetic deviation. The error varies depending on where you are. If you want to be very precise, find the magnetic variation of your location and adjust the compass-sundial to compensate. At my location the variation is about negative 5 degrees, meaning the magnetic needle is pointing 5 degrees west of true north. A very slight rotation of the body of the compass and the sundial pointer can be done, but on the small gadget it's hard to get that right, so you can ignore it....at least for my purposes.
Don't forget that a sundial gives you...wait for it....sun time, not daylight saving time, so you need to correct for that, if appropriate.
They aren't precision instruments, but are fun to play with. I just checked mine at 10:20 eastern daylight savings time, and it told me it was 9:30 sun time.
Spence
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Post by Black Hand on Sept 12, 2019 14:11:13 GMT -7
I've got one in the bottom of my gun bag - used it once (if even that). I tend to navigate by dead-reckoning with fairly good success.
The story is that one from the period was found in a burnt-out cabin and was used as the model upon which the new ones are based. No idea how accurate this story might be, but it is a neat gizmo (one of those "buy-before-thinking/researching" purchases from early on).
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Post by spence on Sept 13, 2019 6:14:11 GMT -7
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Post by Sicilianhunter on Sept 13, 2019 22:03:43 GMT -7
I found this article:
How to Use a Sundial Compass
The compass and the sundial are two completely different instruments which were built for entirely different uses.
The compass is an instrument that is used for navigation and includes a free-floating magnetized needle which, when held level and still, aligns itself with the earth’s magnetic field and in doing so, points approximately north.
The sundial is an instrument that is designed for a specific location on the earth and permanently installed there so that the shadow of one of its parts indicates the hour of the day. Of course, this only works during daylight hours and when the sun is making shadows.
Combining the Function of a Sundial and Compass
A sundial compass is a combination of these two instruments, consisting of a portable sundial which is attached over a compass via a hinge. There are some adjustable legs that need to be used to level the instrument if not on level ground. The gnome is hinged and needs to be put in the up position where it locks into place. There should be what looks like a protractor that is to the right of the gnome that is on a hinge, and this needs to be flipped up as well. The protractor is used to set the sundial to the correct latitude angle, while the compass is used to find true north based on the area’s magnetic north declination.
Once your sundial compass has been leveled, set to the correct latitude, and to true north, a shadow will be is cast onto the sundial’s face by the gnome. For use in the southern hemisphere, the same procedure is followed with the exception that true South must be found instead of true North.
Storing & Transporting our Sundial Compass
When the instrument is not in use, the needle brake should be set to ensure that the needle bearing is not damaged in transit. To accomplish this, the lever on the side of the compass is simply slid over, locking the needle in place. Then, the sundial and gnome are folded over for storage.
Allowing for Location in Your Sundial Compass “Reading”
The time shown on the sundial may not match the time on your clock or watch, however. This is because the time shown on the sundial is actually the “local apparent time” due to the fact that times are based on the position of the sun at the center of the time zone. The sundial will be ahead if you are on the east side of the time zone and behind if you are on the west side.
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Post by straekat on Sept 14, 2019 4:05:22 GMT -7
I can tell direction without a compass at sunrise & by the stars at night, & I can keep a straight line without a compass, but using a compass to maintain direction in all weather conditions is far easier. I have never used the sundial, I can tell the time well enough without it. Besides which it is calibrated for the Northern hemisphere. Keith.
Being able to navigate by sun, starts, sensitivity to wind-direction, in addition to being able to judge time of day or night within ten minutes (max) without any other aides, forming a mental map of the topography of the landscape around you, how far you've moved in any direction even if it involves course changes are all skills that can be developed through practice.
If someone told me they could do that when I was in my teenage years, I wouldn't have believed or seriously doubted them. Fast forwards to my thirties and after spending literally years being outside in the African veldt and the Great Plains in the American West, I'd picked up most of them without even trying. I still use them more often than not, although for the life of me, somehow I don't remember to take my cell phone when I leave the house.
Keith, good point on bring up sundials are calibrated for either northern or southern hemisphere's. That along with the Coriolis affect, different star maps between the hemisphere's can require mental adjustments when going down under, or for the "undies" to head up and over.
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Post by Sicilianhunter on Sept 14, 2019 22:13:45 GMT -7
LeLoup, Got mine in the mail today, 2 days earlier than anticipated and its exactly the same as the one you depicted! Its actually got some weight to it. After reading the article I posted I was under the impression it lifted out of the lower half for the combination sundial/compass function but that doesn't seem to be happening... BTW, in regards to maintaining direction in all weather conditions: during a deer hunting in PA a light drizzle fell when there had been an ice storm days before which made for a fast fog. If it weren't for my compass then I would've never have know I was walking in circles... I don't always use it but ever since then I always have one with me
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Post by artificer on Sept 19, 2019 8:20:53 GMT -7
SH,
Before I came on active duty, I read as much as I could in the "Pre-Computer Age."
One thing I got from reading historical accounts then was when traveling through areas you are not familiar with, you should turn around occasionally and look back on the direction you came from. The view looking back can be quite different than the view when looking forward and especially if the light conditions change significantly. Really helps one from going in circles when the clouds cover the sun or it begins raining/snowing. I used this tip many times on active duty and it works great.
I also went Coon Hunting at night for three seasons before I came on active duty. We did not walk with lanterns/lights on and only turned on the lanterns/lights when we actually went to shoot the Coon. We hunted through corn and other fields, woods, sloughs/swamps, up and down fairly steep hills, etc. You wind up developing an unconscious sense of whether a dark spot has a hole in it or not or other things to avoid without thinking, when walking even through areas new to you. Not sure how it is done physically, but it does work. There is no doubt in my mind folks back then also found this out after they moved around enough at night without candle lanterns.. Gus
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Post by jrmflintlock on Sept 21, 2019 15:49:10 GMT -7
Great thread! I don’t worry too much about time when in the woods, but direction is always important. I have always wanted one too as the compass buried in my shooting pouch is hardly PC. And it rarely comes out. But it’s nice to know I have it when I ever need it. I may have to invest in one. Just because!
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Post by Sicilianhunter on Sept 25, 2019 6:15:42 GMT -7
SH, Before I came on active duty, I read as much as I could in the "Pre-Computer Age." One thing I got from reading historical accounts then was when traveling through areas you are not familiar with, you should turn around occasionally and look back on the direction you came from. The view looking back can be quite different than the view when looking forward and especially if the light conditions change significantly. Really helps one from going in circles when the clouds cover the sun or it begins raining/snowing. I used this tip many times on active duty and it works great. I also went Coon Hunting at night for three seasons before I came on active duty. We did not walk with lanterns/lights on and only turned on the lanterns/lights when we actually went to shoot the Coon. We hunted through corn and other fields, woods, sloughs/swamps, up and down fairly steep hills, etc. You wind up developing an unconscious sense of whether a dark spot has a hole in it or not or other things to avoid without thinking, when walking even through areas new to you. Not sure how it is done physically, but it does work. There is no doubt in my mind folks back then also found this out after they moved around enough at night without candle lanterns.. Gus That is some good advice! When using a modern compass to shoot an azimuth I always pre-set my back azimuth so I can follow it to my starting point. Looking back would help in a similar way when using a period compass
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Post by Sicilianhunter on Sept 25, 2019 6:17:44 GMT -7
JRM, So true! I'd rather have it and not need it than need it and...well you know the rest!! Happy to see you!!
The Sicilian
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Post by Leifer on Oct 7, 2019 15:56:00 GMT -7
I had one that I used quite a bit like shown at the beginning of the thread. I was able to figure within 15 minutes of the actual time. That being said, time in the woods operates differently, however, it's nice to have a relative idea of what time it is or what kind of time has passed.
Leifer
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Keith
City-dweller
Bushfire close but safe now. Getting some good rain.
Posts: 990
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Post by Keith on Oct 7, 2019 17:06:09 GMT -7
I had one that I used quite a bit like shown at the beginning of the thread. I was able to figure within 15 minutes of the actual time. That being said, time in the woods operates differently, however, it's nice to have a relative idea of what time it is or what kind of time has passed. Leifer I have this habit of going into the woods & sitting on some mossy log looking & listening, forgetting why I am there in the first place & suddenly it is getting dark! Keith.
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Post by straekat on Oct 10, 2019 10:11:19 GMT -7
Ok...question.
The cardinal directions can be determined using a pocket (or a watch worn the wrist that hasn't been invented yet....). I was taught how to use one during my wet-behind the ears stage as a boy scout. Anyone else know how to use a watch to determine north, in addition to knowing which hands Mickie is pointing to?
As an aside, there are some neat reproduction period watches that have been appearing on the market in the last few years. They are battery driven and not true stem winders. These aren't the "Walmart" cheap specials based on 19th and 20th century "hunter patterns."
Now that I mentioned period watches, that's fodder for another thread.
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