So I bought a sextant, and I intend to learn. If only I could get the coveted Navigator Certificate.
Got a few Nav winged guys in my unit who were "table-Nav's" in the -135 and the -130. I posed the question to them and they said it was like riding a bike, so far as remembering how to use one.
Yeah, that's what I've heard, it's kind of a pointless exercise in time wasting when even the average VFR only airplane has ten types of GPS, a VOR, an ADF etc. It is interesting however. It's kind of a lost art.
Yeah, even fix to fix direct off a VOR, or dead reckoning off the ground are going away. Cell Nav is pretty much gone. From what I hear they don't even teach it in NAV school anymore.
I've always wanted to do that. Where did you get you sextant at?
I bought a non-leveling practice plastic sextant from western marine.
http://www.westmarine.com/webapp/wc...11?&cid=chanintel&ci_src=14110944&ci_sku=1611
You're right, they don't. I can remember being at the old Mather AFB in Sacremento, where they had this IMAX-type theatre that showed outer space, and where they'd teach stars, constellations, etc and celestial nav. I believe they stopped teaching it 3 years ago or so.
Hey buddy,
Glad to hear your interest in a dying art. As I understand it they don't even teach it to military navigators anymore, which Im not convinced is a good idea. GPS can be jammed or attacked. Nothing will jam cel, except a vast area of high overcast.
Pretty much impossible to get a good height observed of a cel body with a marine sextant (that would be useful for navigation). You would need to have a sextant with a bubble to give an artificial horizon.
Using a marine sextant from a boat, you can do a easy horizon calculation for your small height above the surface, not so in a plane. Also aerial sextants allow for an averaged observation and have some sort of mounting to hold it steady.
If you wanted to practice on the ground, and could get one, I would recommend the older sextants that they used in the astrodomes of old airplanes. In the Navy I had to use a periscopic sextant, which would be useless for your purposes.
I would love to get back into it if I ever have time to do some sailing, and it was probably the most challenging thing I ever did in aviation.
I guess so...Could I just glue a couple of levels onto the body of the instrument, and match the bubbles up and then shoot my sight? Not really useful in the airplane, nor will I probably ever use celnav in the airplane, but still, a curiosity. I've been reading a lot about it, and damn that stuff is cool. Pressure nav is pretty cool too.
Could I just glue a couple of levels onto the body of the instrument, and match the bubbles up and then shoot my sight? Not really useful in the airplane, nor will I probably ever use celnav in the airplane, but still, a curiosity. I've been reading a lot about it, and damn that stuff is cool. Pressure nav is pretty cool too.
I guess so...
The bubble also acts as the horizon. It creates a level plane so you put the star, planet, son or moon in the center of the bubble and dont see the actually horizon.
We used the intercept method for shooting and plotting the LOP. I think this is different from what sailors do.
Pressure Nav????
Section 15A— Pressure Differential Techniques
15.1. Basics. Pressure differential flying is based on a mathematically derived formula. The formula predicts windflow based on the fact that air moves from a high pressure system to a low pressure system. This predicted windflow, the geostrophic wind, is the basis for pressure navigation. The formula for the geostrophic wind (modified for a constant pressure surface) combined with in-flight information makes available two aids to navigation: Bellamy drift and the pressure line of position (PLOP). Bellamy drift gives information about aircraft track by supplying net drift over a set period of time. Using the same basic information, the PLOP provides an LOP as valid as any other type.
Modern aerial sextants used a mechanical averager as you kept moving the height adjuster dial for two minutes, one each side of fix time. Trying to take an instantaneous observation at fix time would be avpretty tall order.How long would it take to get all the levels lined up for you to shoot your star and also mark the time you took your observation? The longer it takes you your accuracy/precision of your celestial fix will suffer - but the upshot is that you'll get better the more you work with it.
Even on the surface side of it - the Navy uses a program called STELLA now where you put in your estimated position at the time you intend to take your observation - the program then tells you which stars to use and relieves you of having to go through the Air Almanac.
I never thought of the differences required for an aerial observation and a surface observation. At least on the surface side if you didn't have a visible horizon you couldn't take a celestial fix. It was interesting to hear about the bubble level.
Pressure Pattern Navigation:
From this airfroce document I found.
Though I doubt I could calculate it.
My head hurts just thinking about it.
Any book recommendations on celestial nav? I found some PDFs called "American Practical Navigator" but that's it so far.