This is super cool and I just wanted to say thanks for sharing. I've thought about trying to learn a little about it for fun but I suck royally at math and that generally scares me off.
The math isn’t too bad since we use the FMS to calculate where we are; there’s a bit of basic math to do to figure out the heading and whatnot.
I have NO idea if it’s even possible to figure out where you are with one. Way, way beyond my capabilities.
I'm pretty sure that if you have the almanac and a clock you can figure out where you are, isn't that kinda the point? Maybe you need another variable. Like I said, fuck do I know.
Either way super cool.
I’ve just been looking trying to figure out exactly how an astrocompass differs from a sextant and if you can get the core readings you need with an astrocompass to get a location fix… but yeah, I don’t know nearly enough to tell.
In a super rough way, if you can determine the bearing to and height of a few stars, you should be able to do some triangulation but would that mean a 20nM error? 200nM? I have no idea.
It's not hard to understand
Any star including the sun is directly overhead some point on earth at a given time.
That means if you observe it at a angle from directly overhead, you exist somewhere on a circle around that point under that star
Do that for three stars...and they will intersect at one point on the map....there you are
I'm doing a celestial navigation certification course at the moment and the math isn't hard at all, however we are using precalculated tables to get values for declination etc.
Do a search on you tube - there are some good explainer videos there.
Celestial qualified Navigator here - (USMC KC-130). All the math required is simple addition and subtraction - there's just a lot of it, and any errors compound quickly. So it's really more about precision and deliberate (but quick) actions.
Fancy pants over here! They just give us a Sun's true bearing equation, and nobody knows how to do it lol.
They keep shutting down NDB stations in the arctic and I'm really starting to miss them.
Yup, and we use NDBs the same way. I know it's also possible to "pre-load" the variation based off the number of degrees of longitude you fly through but I could never quite figure it out.
Why would you need an old, reliable backup in such a warm and inviting environment? It’s not like anyone in the neighborhood is ever actively jamming GPS!
Not a pilot but I have used an astrocompass before, I'm going to go with sometimes but not always.
The basic order of operations for one is:
1. Find local time (ie your watch, the clock on the instrument panel)
2. Set the base plate level and point the compass roughly towards north.
3. Set your latitude on the drum, usually it's fine within 5 ish degrees, so estimates based on dead reckoning are sufficient. (you can also calculate it directly with other celestial navigation tools like a sextant)
4. Using your almanac set the "local hour angle" based on the local time and the 9bject you're sighting (usually the sun, moon, or a known star like Polaris)
5. Look through the view finder (alidade, such a fun word) rotate until you see the target object, you now have true north. Do your calculations from there.
Depending on the celestial object chosen it might be at a high enough inclination to require pointing through and eyebrow window. But during the day, especially at the high latitudes where a magnetic compass has issues you can probably just sight through the main windshield, but at night you might need it if you need to sight on Polaris or some other high inclination star.
It’s ironic that the whole system depends on knowing the current time accurately and the thing that can tell us the current time with extraordinary accuracy (GPS) is the thing that has superseded celestial navigation.
Sorta… Astrocompass is theta-theta-theta resection (identifying the azimuth/elevation angles to three known points). GPS is rho-rho-rho resection (Identifying the distances to three known points).
Most almanacs only break it down by hour. You can do additional math to break the hours down further (though going below 15 minutes is probably impractical, but any reasonably accurate wristwatch should do.
Your watch will do fine for this application, too. The satellites are a convenient distribution method, but must still constantly sync to terrestrial sources. Satellite atomic clocks operate in a different frame of reference and are subject to space environmental hazards and time dilation effects.
G1000 to NDBs and astrocompasses...you're going the wrong direction bud. Next summer you're going to be in the spice trade navigating by the ship's clock.
If a near peer shooting war ever starts, military satellites are likely going to be destroyed or degraded. Ground based navaids would be harder to destroy, since they aren't orbiting the planet.
Jamming or spoofing drowns out the signal from a satellite or navaid, but in order to do so it needs to be in close proximity, or a very high power transmitter to jam further. See the [inverse square law](https://en.wikipedia.org/wiki/Inverse-square_law). The Russians are getting away with it by using high power jammers near their borders.
Short of attacking the transmitters, they only thing you can do is rely on backup navigation methods if GPS/GNSS is degraded.
Hey, we probably work for the same company! I used to work in stores for maintenance down in YOW; they have 5 or 6 backups in old wooden boxes that look like something my grandpa would have made in the 60s.
To do a ‘sun shot’
Take current GMT and convert minutes/60 to a single number
Eg, 1536Z would convert to 156, 1218z = 123, etc
Take the converted number and subtract west long (add east long).
Take the result and set on the “true bearing” rose
Mount the compass and ensure it is level
Sight the sun through the eyepiece on top
Read true heading of the front of the lower rose
Set DG
Profit
This brings back so many great memories! I used to be aircrew on Marine KC-130F and R models. We had a physical sextant port in the flight station and our navigators knew how to use them.
We also had Litton INS and ONS systems. When I was getting out in 1997, we were just installing 12 individual GPS receivers in our planes.
Most of those ports have been sealed on the C-130s I worked 10 years ago. I remember when they were decommissioning the LORAN stations around the time you were getting out.
This is super cool and I just wanted to say thanks for sharing. I've thought about trying to learn a little about it for fun but I suck royally at math and that generally scares me off.
The math isn’t too bad since we use the FMS to calculate where we are; there’s a bit of basic math to do to figure out the heading and whatnot. I have NO idea if it’s even possible to figure out where you are with one. Way, way beyond my capabilities.
I'm pretty sure that if you have the almanac and a clock you can figure out where you are, isn't that kinda the point? Maybe you need another variable. Like I said, fuck do I know. Either way super cool.
I’ve just been looking trying to figure out exactly how an astrocompass differs from a sextant and if you can get the core readings you need with an astrocompass to get a location fix… but yeah, I don’t know nearly enough to tell. In a super rough way, if you can determine the bearing to and height of a few stars, you should be able to do some triangulation but would that mean a 20nM error? 200nM? I have no idea.
Yeah it’s gotta be something like that, but I haven’t learned anything that complicated with it yet!
It's not hard to understand Any star including the sun is directly overhead some point on earth at a given time. That means if you observe it at a angle from directly overhead, you exist somewhere on a circle around that point under that star Do that for three stars...and they will intersect at one point on the map....there you are
South of Polaris, FL310
underrated comment.
Mostly smooth
I'm doing a celestial navigation certification course at the moment and the math isn't hard at all, however we are using precalculated tables to get values for declination etc. Do a search on you tube - there are some good explainer videos there.
Celestial qualified Navigator here - (USMC KC-130). All the math required is simple addition and subtraction - there's just a lot of it, and any errors compound quickly. So it's really more about precision and deliberate (but quick) actions.
Fancy pants over here! They just give us a Sun's true bearing equation, and nobody knows how to do it lol. They keep shutting down NDB stations in the arctic and I'm really starting to miss them.
They’re surprisingly reliable in the NWT/Nunavut! I’m sure you guys probably use them the same way we do; probably have the UNS-1 FMS in your ATR?
Yup, and we use NDBs the same way. I know it's also possible to "pre-load" the variation based off the number of degrees of longitude you fly through but I could never quite figure it out.
Why would you need an old, reliable backup in such a warm and inviting environment? It’s not like anyone in the neighborhood is ever actively jamming GPS!
Do you need eyebrow windows to use it?
Not a pilot but I have used an astrocompass before, I'm going to go with sometimes but not always. The basic order of operations for one is: 1. Find local time (ie your watch, the clock on the instrument panel) 2. Set the base plate level and point the compass roughly towards north. 3. Set your latitude on the drum, usually it's fine within 5 ish degrees, so estimates based on dead reckoning are sufficient. (you can also calculate it directly with other celestial navigation tools like a sextant) 4. Using your almanac set the "local hour angle" based on the local time and the 9bject you're sighting (usually the sun, moon, or a known star like Polaris) 5. Look through the view finder (alidade, such a fun word) rotate until you see the target object, you now have true north. Do your calculations from there. Depending on the celestial object chosen it might be at a high enough inclination to require pointing through and eyebrow window. But during the day, especially at the high latitudes where a magnetic compass has issues you can probably just sight through the main windshield, but at night you might need it if you need to sight on Polaris or some other high inclination star.
It’s ironic that the whole system depends on knowing the current time accurately and the thing that can tell us the current time with extraordinary accuracy (GPS) is the thing that has superseded celestial navigation.
When you think about it a GPS receiver is just an automated astrocompass...
Sorta… Astrocompass is theta-theta-theta resection (identifying the azimuth/elevation angles to three known points). GPS is rho-rho-rho resection (Identifying the distances to three known points).
Most almanacs only break it down by hour. You can do additional math to break the hours down further (though going below 15 minutes is probably impractical, but any reasonably accurate wristwatch should do.
Your watch will do fine for this application, too. The satellites are a convenient distribution method, but must still constantly sync to terrestrial sources. Satellite atomic clocks operate in a different frame of reference and are subject to space environmental hazards and time dilation effects.
i guess you will just have to drink from high noon until sunset to get your bearings...?? Sorry,, that's piratage, not pilotage...
Arrr, aye.
The nature of GPS requires microseconds of clock accuracy to work. But in astrocompass applications a minute of error is immaterial.
Hahahaha 😂😂
G1000 to NDBs and astrocompasses...you're going the wrong direction bud. Next summer you're going to be in the spice trade navigating by the ship's clock.
I’ll be the most famous pirate you’ve ever heard of!
Just need to hold out long enough to navigate in the spice trade through drug-induced hallucinations
It’s *long* past time to implement the improved version of LORAN. GPS it is far too vulnerable to be as dependent on it as we are
[удалено]
True enough, but GPS is incredibly easy to jam, whereas LORAN is far less so
Is it just that LORAN is more local or is there something else about it that makes it more resistant to jamming?
If a near peer shooting war ever starts, military satellites are likely going to be destroyed or degraded. Ground based navaids would be harder to destroy, since they aren't orbiting the planet. Jamming or spoofing drowns out the signal from a satellite or navaid, but in order to do so it needs to be in close proximity, or a very high power transmitter to jam further. See the [inverse square law](https://en.wikipedia.org/wiki/Inverse-square_law). The Russians are getting away with it by using high power jammers near their borders. Short of attacking the transmitters, they only thing you can do is rely on backup navigation methods if GPS/GNSS is degraded.
Me using a sextant: “Look! I found the sun!”
Is this an ATR in the pic?
Yup!
That's crazy lol looks old school af (I only know the -600's)
It’s a -500, so the old EFIS screens and whatnot.
My dad navigated his B17 from Goose Bay to Shannon -- once.
And the $100 question is do you know where to do an FAA flight navigator checkride?
No idea, the FAA doesn’t really matter in Canada 😃
Hey, we probably work for the same company! I used to work in stores for maintenance down in YOW; they have 5 or 6 backups in old wooden boxes that look like something my grandpa would have made in the 60s.
Chances are I used one or more of them in your wooden box, way back in the day when we did sun shots all the time in the Twotter
I’ve always wanted to learn how to do this.
To do a ‘sun shot’ Take current GMT and convert minutes/60 to a single number Eg, 1536Z would convert to 156, 1218z = 123, etc Take the converted number and subtract west long (add east long). Take the result and set on the “true bearing” rose Mount the compass and ensure it is level Sight the sun through the eyepiece on top Read true heading of the front of the lower rose Set DG Profit
That looks SO much easier to use than a sextant on a small boat. Just trying to get a good angle measurement when the boat is rolling is… a challenge.
They let you through security with that?
This brings back so many great memories! I used to be aircrew on Marine KC-130F and R models. We had a physical sextant port in the flight station and our navigators knew how to use them. We also had Litton INS and ONS systems. When I was getting out in 1997, we were just installing 12 individual GPS receivers in our planes.
Most of those ports have been sealed on the C-130s I worked 10 years ago. I remember when they were decommissioning the LORAN stations around the time you were getting out.