Celestial navigation by day

[Pilot_76]

Originally Posted by kylania

I don't use it in Silent Hunter 4, but Silent Hunter 5 has a very robust Real Navigation system. I'm still not that good with finding my location via sextant, so I rely on the navigator, but it's still a fun experience.

kylania, how's the cel nav mod working in SH5 today? I'm currently concentrating on SH4 only. Is there a MOD to implement a sextant sight? I know that a MOD has a navigator plotting the DR position (no more moving sub icon) but to take the sights yourself would be much better.

[ETsd4]

Originally Posted by Pilot_76

how's the cel nav mod working in SH5 today?

Calculating 1 star for a 3-star position fix in SH5:

Mod: SH5 true navigation = SH5 real navigation without any AI

[Pilot_76]

Originally Posted by ETsd4

Calculating 1 star for a 3-star position fix in SH5:

Mod: SH5 true navigation = SH5 real navigation without any AI

OMG!! Is this from TheDarkWraith's mod?? Can't get any more real than that...

[ETsd4]

Originally Posted by Pilot_76

OMG!! Is this from TheDarkWraith's mod?? Can't get any more real than that...

The basic is TDW's real navigation. For additional tools look here under "equipment" => http://www.subsim.com/radioroom/show...&postcount=110 Also you need stellarium v11 and higher, which emulates the real refraction of stars and planets.

[Rockin Robbins]

Is the difficulty with using a sextant on a submarine simulated? Using a sextant on a moving boat is another world from using it on dry land. How about atmospheric refraction and scintillation? Scintillation alone can make a 1º position difference in a star, forget about measuring minutes and seconds!

Thankfully, over the open water, the atmosphere tends to be much steadier than over land but scintillation and refraction are variable effects having different importance for each individual observation.

But that ability to actually do the mechanics of reducing observation to position is an incredibly valuable experience.

Now, in SH5 are the navigational map and tactical plot combined as in SH4 or do they have completely separate navigation and tactical plots? Because in SH4, introducing manual positioning destroys your tactical ability. In reality they were completely separate functions.

Edit: Yup! The refraction correction is there! Well done. Is that built into the game or did you introduce it with your mod?

[Pilot_76]

Originally Posted by ETsd4

The basic is TDW's real navigation. For additional tools look here under "equipment" => http://www.subsim.com/radioroom/show...&postcount=110 Also you need stellarium v11 and higher, which emulates the real refraction of stars and planets.

Speaking of Stellarium a realistic way of simulating a sextant sight in there would be getting the apparent alt. instead of geometric when you click on any celestial body correct? If I'd like to have more errors as in real life would it be more realistic by using the angle tool and measuring myself?

[Rockin Robbins]

Originally Posted by Pilot_76

Speaking of Stellarium a realistic way of simulating a sextant sight in there would be getting the apparent alt. instead of geometric when you click on any celestial body correct? If I'd like to have more errors as in real life would it be more realistic by using the angle tool and measuring myself?

That's what ETsd4 means when he says "which emulates the real refraction of stars and planets." It is the lens-like refraction of the light from astronomical bodies that shifts their positions, varying mostly by altitude above the horizon, but also in a lesser way by temperature and atmospheric pressure. In practice, you only need to consider the effect of altitude because positional shifts caused by the other two are smaller than the variations in your ability to measure.

[Pilot_76]

Originally Posted by Rockin Robbins

That's what ETsd4 means when he says "which emulates the real refraction of stars and planets." It is the lens-like refraction of the light from astronomical bodies that shifts their positions, varying mostly by altitude above the horizon, but also in a lesser way by temperature and atmospheric pressure. In practice, you only need to consider the effect of altitude because the other two are smaller than the variations in your ability to measure.

The thing is that when getting the geometric alt which in my understanding the the most accurate and using the apparent I get a huge difference from my assumed position (DR). In real life what is a good margin of error acceptable between actual position and Assumed position? I kind of find that using the geometric (once I was only 700 yards apart!!) is cheating.

[Pilot_76]

BTW, regarding finding your position with the sun other than using the "LAN" or noon shot, I found this:

http://www.oceansail.co.uk/Downloads...Reduction.html

[Rockin Robbins]

No matter when you shoot the sun its position is beastly difficult to determine due to its position. The thing is big, half a degree in diameter and it heats the air up something fierce, making it swim all over the place like a blob of jello.

All that uncertainty can be boiled down into an error deviation in your position that would be quite large. That's not to say that it isn't better than having absolutely no idea! Navigators sometimes grab anything available in their quest to avoid COMPLETE ignorance....

Even in a three star computation done on dry land you end up with a triangle drawn, and your position is "somewhere in this here triangle." And from repeated use, you get an expectation of how large the triangle should be. If it's way too large, you start looking for computational or observational errors. If you find none, you do the whole blasted thing over again. "Hey Cap, can we surface again?"

[Pilot_76]

Originally Posted by ETsd4

The basic is TDW's real navigation. For additional tools look here under "equipment" => http://www.subsim.com/radioroom/show...&postcount=110 Also you need stellarium v11 and higher, which emulates the real refraction of stars and planets.

ETsd4, I think I understand now. The apparent altitude takes account the refraction and other "real" factors from the real declination. Using the geometric alt. in Stellarium would be cheating or having a super sextant with a bionic eye attached taking accurate readings...So using the apparent altitude is much more realistic.


In one of the forums at stellarium's page they state that the altitude that you set is to simulate the refraction and atmosphere. Not the actual altitude of the observer. Since in SH you are always at sea setting zero or 2000m won't make a difference in the sextant reading.