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+--- Thread: new artificial horizon (/showthread.php?tid=223)
new artificial horizon - pabrides - 02-27-2021
Try to imagine this, shipmates.
I plan to make a sort of horizon in my yard.
My plan is to use a long clear plastic thin hose filled with water to help mark a spot on my fence. The 2 hose ends will show an equal water level, so the hose snakes along the ground but is risen at both ends. If one end is at eye height at some place where I stand to use a sextant, and the other end, perhaps 20 or 30 feet distance, is raised at the fence with a white paper tacked to the wall at the height of the water level, then I have a horizontal line of sight equal to that of the natural horizon with no dip. As long as my eye level is steady and nearly equal to the water height in the tube, I can bring down the sun, moon, or other body to the edge of the white paper to get hs.
Instead of a white paper which would give me a very narrow azimouth, i could stretch a level, easy to see string, like orange surveyors string, along my fence to give myself more azimuth. A tight string around the whole back yard at eye height would allow a shot in any direction, but I only need, because of trees, about 45 degrees of azimouth.
Without a fence one could drive poles into the ground with which to stretch a leveled string. I'm sure some of you could invent other ways as well to support a highly visible string at eye height. At night for star or planet shots the string could be illuminated with a flashlight or some other means. It's not perfect, but it gives me something with which to play other than an oil filled dish. A nice lazer level would serve the same purpose - that is to mark equal eye heights at two places where one could take a shot.
So, what do you think? Does this sound doable?
Cheers.
RE: new artificial horizon - EdCa - 02-27-2021
That's a very good idea. Here's something to make it, sometimes, easier (which you probably already know);
- Setup your horizon as mentioned.
- From the location on your property where you'll be taking the actual observations (where your 2 feet stand) use the Sun to determine your exact latitude, or, set your sextant to the reading of Ho (yes, Ho) and measure the Sun's altitude at the time when the Sun's on your meridian. The error between Ho and Hs will indicate your He (Height of Eye) figure that should be somewhat constant. Take into consideration breathing also- when you inhale you become taller and it's enough to effect your observation. So, inhale, then take the shot.
It will be a different figure if you have shoes on and then make another observation with your shoes off.
I've used your method for determining latitude except mine's not a improved as yours is. Meridian passage is calculated and then I just use a fence rail as the horizon. All sights are taken from a common point- our sidewalk with me wearing no shoes.
Your string and light idea is perfect.
Ed
RE: new artificial horizon - craigsl - 03-02-2021
How'd it work out for you, Pabrides?
Sounds very interesting the workable.
Craig
RE: new artificial horizon - pabrides - 03-02-2021
(03-02-2021, 12:34 AM)craigsl Wrote: How'd it work out for you, Pabrides?
Sounds very interesting the workable.
Craig
Works ok... my eyes are a bit old so a string is a bit of a challenge, but its more fun than a reflecting dish and accurate enough.
The farther the string from the place where you stand the more accurate, given the string is at eye height,, but the farther the string the more difficult to see. You'll just have to experiment to see what works best for you.
The plastic water filled tube works great to provide equal heights of eye and string. its even more accurate than those little bubble levels. The tube is also used to level the string. So, first decide your range. Then you level one string end with eye height at the sextant position. Then level the other string end and double check by measuring the string ends together with the tube. Make sure the string doesn't sag.
Using the tube is kinda tricky at first but you soon learn the best way to measure with it. Just remember that when you adjust either tube end up or down double check the other end that the water level is where you want it. Cant beat mother nature's gravity for accuracy and an unsteady hand to screw it up... lol
One more thing. It works best if you have a way to mark eye height at the sextant position. A tall stake pounded in the ground marked with eye height gives you a permanent range of equal heights. Viewing across the near eye height mark to the string would point directly to the natural horizon... so then you dont have to always wear the same shoes or assume the same posture when taking an observation. An inch or two up or down from the near mark, depending on distance to the string, will probably not make that much difference in the observation.
Good luck. Dont forget to tell us if you try it.
Cheers