Would you be interested in realistic celestial navigation?

The "Queen of the Skies"

Would you be interested in realistic celestial navigation?

Poll ended at 18 Oct 2019, 08:04

Yes, that would be my primary means of navigation
1
11%
Yes, I would use it from time to time for fun
4
44%
Yes, I would try it once or twice
1
11%
No, it's too complex to learn
2
22%
No, ADF/VOR/GPS is enough for me even if unrealistic
1
11%
What is celestial navigation?
0
No votes
 
Total votes: 9

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ilya1502
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Would you be interested in realistic celestial navigation?

Post by ilya1502 »

That is, if there were realistic models of A10 sextant and MkII astrocompass plus an update for stars and constellations in the sim (there are several out there already), that would require using Air Almanac and Navigation Tables and all the calculations to reckon your position? When it's authentic and appropriate, like when flying Connie, B-17, C-47/DC-3.

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DHenriques_
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Re: Would you be interested in realistic celestial navigation?

Post by DHenriques_ »

Celestial Nav is complicated enough that both what the user would have to know AND the programming necessary to accurately provide what was needed in a sim to allow the user to apply it and arrive at the answers needed for realistic navigation would require enough code to choke a T-Rex.
If you think you are having a frame rate problem now, just wait until you start messing with celestial navigation,
:-))))))))))
Dudley Henriques

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ilya1502
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Re: Would you be interested in realistic celestial navigation?

Post by ilya1502 »

DHenriquesA2A wrote: 11 Oct 2019, 08:22 Celestial Nav is complicated enough that both what the user would have to know AND the programming necessary to accurately provide what was needed in a sim to allow the user to apply it and arrive at the answers needed for realistic navigation would require enough code to choke a T-Rex.
Celestial Nav is complicated no doubt, but I think you are exaggerating a possible performance impact. The guys here are testing a working sextant model for FS9/FSX/P3D. I think it's some older bitmap, but the code is all new. I'm using it, too, and the performance impact is negligible.

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DHenriques_
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Re: Would you be interested in realistic celestial navigation?

Post by DHenriques_ »

ilya1502 wrote: 11 Oct 2019, 09:34
DHenriquesA2A wrote: 11 Oct 2019, 08:22 Celestial Nav is complicated enough that both what the user would have to know AND the programming necessary to accurately provide what was needed in a sim to allow the user to apply it and arrive at the answers needed for realistic navigation would require enough code to choke a T-Rex.
Celestial Nav is complicated no doubt, but I think you are exaggerating a possible performance impact. The guys here are testing a working sextant model for FS9/FSX/P3D. I think it's some older bitmap, but the code is all new. I'm using it, too, and the performance impact is negligible.
You could of course fudge it but to accurately depict what is necessary to obtain an accurate fix using a sextant you would require an accurate sky with bodies in exact coordinates and at exact time. That would be a tremendous effort on code.
But as I say, you can always fudge it but don't expect whatever is fudged to anywhere even near accurate. Just doing the math and printing out the required logs to match real world conditions would be a real task.
Keep in mind here that I'm talking REAL celestial navigation capability. Anyone could come up with a workable program using faux code. If done for a desktop sim program it would have to be based on a fixed atmosphere without changing star position etc. Doable but no where near actual celestial navigation requirement.........that is unless you intend creating an entire planetarium with accurate positioning of the earth in relation to your choice of reference for the fix..........THEN you would need an accurate log.
NOT an easy task for a desktop computer.
I remember during the FSX beta phase this question came up and was tossed around a bit. The general consensus was about my comments above. Just to complex and heavy on the system for the few who would want to go to the trouble of learning what was necessary to use it properly.
But as I said, different strokes for different folks. By all means give it a shot if you like the idea. From a flight instructor's point of view I can tell you that the average pilot out here has minimum ADF skills let alone learning celestial nav. :-)))))

Dudley Henriques
Last edited by DHenriques_ on 11 Oct 2019, 10:41, edited 1 time in total.

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ilya1502
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Re: Would you be interested in realistic celestial navigation?

Post by ilya1502 »

DHenriquesA2A wrote: 11 Oct 2019, 10:17 You could of course fudge it but to accurately depict what is necessary to obtain an accurate fix using a sextant you would require an accurate sky with bodies in exact coordinates and at exact time. That would be a tremendous effort on code.
But as I say, you can always fudge it but don't expect whatever is fudged to anywhere even near accurate. Just doing the math and printing out the required logs to match real world conditions would be a real task.
Keep in mind here that I'm talking REAL celestial navigation capability. Anyone could come up with a workable program using faux code. If done for a desktop sim program it would have to be based on a fixed atmosphere without changing star position etc. Doable but no where near actual celestial navigation requirement.........that is unless you intend creating an entire planetarium with accurate positioning of the earth in relation to your choice of reference for the fix..........THEN you would need an accurate log.
NOT an easy task for a desktop computer.
Well, sir, you are saying words like "fudge" and "faux" about a code you haven't even seen. I think it's a bit... incorrect.

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DHenriques_
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Re: Would you be interested in realistic celestial navigation?

Post by DHenriques_ »

ilya1502 wrote: 11 Oct 2019, 10:40
DHenriquesA2A wrote: 11 Oct 2019, 10:17 You could of course fudge it but to accurately depict what is necessary to obtain an accurate fix using a sextant you would require an accurate sky with bodies in exact coordinates and at exact time. That would be a tremendous effort on code.
But as I say, you can always fudge it but don't expect whatever is fudged to anywhere even near accurate. Just doing the math and printing out the required logs to match real world conditions would be a real task.
Keep in mind here that I'm talking REAL celestial navigation capability. Anyone could come up with a workable program using faux code. If done for a desktop sim program it would have to be based on a fixed atmosphere without changing star position etc. Doable but no where near actual celestial navigation requirement.........that is unless you intend creating an entire planetarium with accurate positioning of the earth in relation to your choice of reference for the fix..........THEN you would need an accurate log.
NOT an easy task for a desktop computer.
Well, sir, you are saying words like "fudge" and "faux" about a code you haven't even seen. I think it's a bit... incorrect.
You're right. I haven't seen the code. But I've seen the folks who create the code and I know celestial navigation.
:-))
As I said, go for it if you like. I just don't think the idea will fly in the community. Too much work to create it for too little return in the customer base who would first want it, or actually use it.
We will simply have to come to a friendly disagreement on this one. :-))
DH

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ilya1502
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Re: Would you be interested in realistic celestial navigation?

Post by ilya1502 »

The credits for the work should go to Alexander Belov. The models have not been publicly uploaded, but can be requested from the author.

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AKar
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Re: Would you be interested in realistic celestial navigation?

Post by AKar »

Having an accurate sky should be trivial. Data is readily available, and the FSX/P3D allows for updates. Having proper era instruments in the sim graphics engine, probably not so easy to do in a convincing way but likely doable. Fundamentally, celestial navigation is simply visual navigation looking up, made seemingly complex by the fact that the "ground" is moving as well.

Nowadays, I wonder if there is any mobile app that would allow you to do (real life) celestial navigation. I mean, you'd point the phone against identified sky feature. The phone has date and time, and can find the local vertical and its angles relative to it. It can also find the magnetic north (of course, you could do a time lapse for it to locate the true north as well). Click, and it would give you a position result result. Talking about how to ruin something with modern gadgets there... :mrgreen:

Edit: Not surprising that some Russian guy has made a simulator application of the theme. They are often very good in this kind of stuff, knowing their math and physics second to none and making very lean computer programming out of it. (Damn I miss the Project Tupolev! :))

-Esa

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Paughco
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Re: Would you be interested in realistic celestial navigation?

Post by Paughco »

I have enough interest in the subject to watch a pretty cool YouTube video posted by AJ Crowley back in March 2017. https://www.youtube.com/watch?v=1Es9Qi8z4is&t=80s. This two video series takes a look at how the excellent freeware bubble sextant add-on gauge works... how to take shots and plot lines of position in Google Earth.

I watched it, and while it seems like a pretty cool concept, I suspect there is a whole lot more to real world celestial navigation than the process described in those videos. It appeared to me to be a way of adding additional complexity to flying a historical transport aircraft, but the added complexity-to-increase in authenticity ratio doesn't work for me. I have since decided that I fly my Connie in the present age, using modern navaids, including VOR, NDB, and yes, even GPS. Sorry, but I like that magenta line that Garmina lays out there on the screen.

More coffee needed.

Seeya
ATB
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ilya1502
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Re: Would you be interested in realistic celestial navigation?

Post by ilya1502 »

Paughco wrote: 12 Oct 2019, 14:00 Sorry, but I like that magenta line that Garmina lays out there on the screen.
And what's in that to be sorry about?

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ratty
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Re: Would you be interested in realistic celestial navigation?

Post by ratty »

ilya1502 wrote: 12 Oct 2019, 15:01
Paughco wrote: 12 Oct 2019, 14:00 Sorry, but I like that magenta line that Garmina lays out there on the screen.
And what's in that to be sorry about?
Too easy. No challenge, no fun.
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Stearmandriver
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Re: Would you be interested in realistic celestial navigation?

Post by Stearmandriver »

I'm late to the party on this one, but anything related to celestial nav intrigues me so I'll have to read through the linked thread where they're working on this!

Is this implementation intending to create a visible and accurate sky in FSX that you actually take sights on and then run sight reductions? Cool idea, but I kind of wonder if it's worth the effort when there's already this gauge:
http://www.kronzky.info/fs/sextant/

I'm the maker of the two video tutorials listed at bottom of page there. That gauge simulates celestial nav pretty realistically in the sim, it just removes the necessity for a truly accurate FSX sky, and performs the sight reduction gruntwork for you, providing you with the distance offset. You still have to perform the (tricky) process of taking a sight with a bouncing bubble, and then plot the resulting distance offset into a line of position. The real world process of running a sight reduction is not actually that complex; the first couple times you do it there certainly seem to be a lot of steps, but they're all just pulling values out of tables and performing simple corrections. Using a worksheet to ensure you don't skip steps, it becomes second nature really quickly. There's no math involved more complex than addition or subtraction; the tables do all the spherical trig for you ;).

Still, I'm intrigued. I love this stuff. I have a couple marine sextants now, and actually just broke down and ordered myself a Christmas present - a refurbed and working A-12 bubble sextant. I'm weird ;). There's something satisfying about actually doing it, though. Looking forward to seeing how accurate the bubble sextant can be!

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Re: Would you be interested in realistic celestial navigation?

Post by Stearmandriver »

AKar wrote: 11 Oct 2019, 11:12 Nowadays, I wonder if there is any mobile app that would allow you to do (real life) celestial navigation. I mean, you'd point the phone against identified sky feature. The phone has date and time, and can find the local vertical and its angles relative to it. It can also find the magnetic north (of course, you could do a time lapse for it to locate the true north as well). Click, and it would give you a position result result. Talking about how to ruin something with modern gadgets there... :mrgreen:
These apps purport to exist, but in reality they simply use gps position to calculate the sextant reading they know you should get. In reality a phone accelerometer is nowhere near sensitive or calibrated enough to give you a usable angular elevation measurement.

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AKar
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Re: Would you be interested in realistic celestial navigation?

Post by AKar »

Stearmandriver wrote: 07 Dec 2019, 04:03
AKar wrote: 11 Oct 2019, 11:12 Nowadays, I wonder if there is any mobile app that would allow you to do (real life) celestial navigation. I mean, you'd point the phone against identified sky feature. The phone has date and time, and can find the local vertical and its angles relative to it. It can also find the magnetic north (of course, you could do a time lapse for it to locate the true north as well). Click, and it would give you a position result result. Talking about how to ruin something with modern gadgets there... :mrgreen:
These apps purport to exist, but in reality they simply use gps position to calculate the sextant reading they know you should get. In reality a phone accelerometer is nowhere near sensitive or calibrated enough to give you a usable angular elevation measurement.
Software calibration of the accelerometers to an accuracy level suitable to find an elevation of stellar object would be trivial. Sensitivity would not be a problem, all modern cellphone accelerometers I've used for any measurement purposes are easily accurate enough to find the phone's orientation for this purpose, though they sometimes have offsets one needs to calibrate out. I have played around with these some, because I'm cheap and don't have proper instruments for the purpose! :mrgreen: (I've actually done some tests where I extracted the three-axis accelerometer 'graphs' in CSV and simply double-integrated the numbers to get a poor-man's inertial reference system. Given the crudeness of my "test setup" - a phone stamped on a dashboard with two-sided tape - the results were surprisingly good, with some caveats. This was some years back. The accuracy would probably be sufficient to create 180° instrument turn back to VMC style app when combined with angular accelerometers, or 'gyroscopes'!)

The obvious question in having a non-cheating app for stellar navigation in a mobile phone is: why? Aside that it would be interesting, of course!

-Esa

Stearmandriver
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Re: Would you be interested in realistic celestial navigation?

Post by Stearmandriver »

Well, the reason that it's interesting is probably the only reason to do anything with celestial nav anymore, excepting marine use. Of course bluewater passages all use GPS for primary nav these days, but you always need a backup method. In modern aircraft, dual (at least) IRSs backup dual GPS receivers... but IRS doesn't work at sea. So even professional mariners still carry sextants and practice celestial, in case of failure of the GPS system; not the receiving system on the ship, but the entire GPS system. I think a lot of people these days take GPS for granted and don't realize how fragile the system is, or how very willing the USAF will be to turn off civilian access at a moment's notice in a national security situation.

Anyway, that's cool experimenting with the cell phone accelerometers, but I think I'd disagree that they're capable of simulating a sextant shot. Sensitive enough, maybe, but I think calibration would be the problem. Even with a fresh calibration, every time I've used the accelerometers for even something as simple as Google Sky map, things jitter around a bit. Maybe only a degree or two, but that equates to 60-120nm of positional error. A good marine sextant can take a sighting accurate to around 1 arc-minute, and a bubble sextant is good to at least 5 arc-minutes.

The Stratux project folks briefly tried to use a cell phone accelerometer for emergency VFR into IMC use and quickly gave up. The gravitational acceleration in a turn quickly fools simple accelerometers. They started working on building and coding a simple AHRS instead; I haven't checked the project in a while, dunno what progress has been made.

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