Navigational stars in Silent Hunter 5

There is good news about the moon. I made a small change to the Page layout.py file that should allow the moon to be used for celestial navigation. Preliminary testing gave good results. I will continue to research. You can update Page layout.py through JSGME by downloading Moon fix for NewSextant from this link:

https://drive.google.com/file/d/1YsP...ew?usp=sharing

To navigate with moon, use a special moon almanac for SH5. Link to the SH5 moon almanac:
https://drive.google.com/file/d/1zBg...ew?usp=sharing

Moon phases:
https://drive.google.com/file/d/1kNg...ew?usp=sharing

I have taken a series of measurements on the moon. All the results indicate that the "graphic" center of the moon (the center of the moon image in the SH5 sky) does not coincide with its "astronomical" center. The image of the moon SH5 in the sky is about 10.3 arc minutes ahead (in the direction of movement of the celestial sphere) and 2.5 arc minutes lower relative to the real moon (regardless of which hemisphere you are in, the readings of the "old" sextant (without refraction without parallax and without dip), when measuring the altitude of the moon, are underestimated by an average of 2.5 arc minutes.In order for the new sextant to give correct readings of time and altitude for the Moon, I made changes to Page layout.py (link to the updated file in the previous post). It worked well for me, so I am starting work on the Lunar Almanac, which will compensate for the discrepancy of 10.3 arc minutes.

[propbeanie]

Is the moon in SH5 "drawn" from a series of moon pictures in one file, and the proper 'phase' of the moon is chosen by "cropping" the image with a menu_1024_768.ini line? That would use one of the corners of the image to place it, instead of the center... maybe??

Originally Posted by propbeanie

Is the moon in SH5 "drawn" from a series of moon pictures in one file, and the proper 'phase' of the moon is chosen by "cropping" the image with a menu_1024_768.ini line? That would use one of the corners of the image to place it, instead of the center... maybe??

To be honest, I don’t know how to correct the graphic image of the moon. IMO, If my solution to the Moon problem works correctly, it might be better not to change the graphical settings of the Moon, just so as not to spoil what works - I'm afraid this could make it a distant prospect of using the Moon for celestial navigation.

[propbeanie]

Your methodology is probably the only way to attempt to correct it, since if you change the crop settings, you'll end up with possibly portions of 3 or 4 different "moons" displaying... might be shades of Jupiter or something... - From what I remember, SH3 uses the upper left corner of an image, while SH4 uses the lower left. I would imagine that SH5 does similar when it comes to grabbing images like that.

I hope, after the holiday season, there is someone with sufficient knowledge to check and confirm that this works or does not work before I recommend this method for use.

[CaptBongTrillion]

Started playing SH5 again when I saw this thread. The research that has been done to make these methods work in SH5 is incredible, and I'm excited to learn more.

I will ask a couple questions since there have been a few folks who offered to take questions.

In the table in Alpheratz's almanac of arc minute and second corrections to GHA, is my time input to the table also GMT - 1 hour like it is above to determine GHA to the nearest 4 hour increment (since my port of departure is Kiel)?

Also, I think I understand how to do the GHA corrections for minutes and seconds, but say if my time input is 2 hours ahead of the nearest 4 hour GHA increment, does that mean in the table of min/sec corrections, I also need to add the corrections for 60min x 2 in order to account for the extra two hours?

I tried figuring out latitude from a Polaris shot and got within ~5 arc minutes but I was using a time input with an hour that matched one of the 4 hour GHA intervals, so I don't think correcting for the hour was necessary. Of course, this could also have been a happy accident because at this point I'm all enthusiasm and zero skill

Thanks again for the amazing work, navigators.

Originally Posted by CaptBongTrillion

Started playing SH5 again when I saw this thread. The research that has been done to make these methods work in SH5 is incredible, and I'm excited to learn more.

I will ask a couple questions since there have been a few folks who offered to take questions.

In the table in Alpheratz's almanac of arc minute and second corrections to GHA, is my time input to the table also GMT - 1 hour like it is above to determine GHA to the nearest 4 hour increment (since my port of departure is Kiel)?

Also, I think I understand how to do the GHA corrections for minutes and seconds, but say if my time input is 2 hours ahead of the nearest 4 hour GHA increment, does that mean in the table of min/sec corrections, I also need to add the corrections for 60min x 2 in order to account for the extra two hours?

I tried figuring out latitude from a Polaris shot and got within ~5 arc minutes but I was using a time input with an hour that matched one of the 4 hour GHA intervals, so I don't think correcting for the hour was necessary. Of course, this could also have been a happy accident because at this point I'm all enthusiasm and zero skill

Thanks again for the amazing work, navigators.

I'll be happy to help you, but I'm not sure yet that I understood correctly what you are asking about. I suggest that you write here all the initial data and your specific example of calculations (for example, as I did in video 3.1), then I will tell you if you are doing something wrong.

I created the table for determining the latitude according to Polaris in a simplified form for educational purposes and the accuracy (max error) of determining the latitude from it is 2-3 arc minutes. If your error was 5 arc minutes, you may have been mistaken at some stage. I am currently working on Nautisches Jahrbuch, which will replace Nautical Almanac. Nautisches Jahrbuch will contain a more accurate Polaris latitude table used by Kriegsmarine.

[CaptBongTrillion]

Ok, here are the calculations. I'm horrible at math, so this might be a bad idea I did leave the boat going 10 knots while I did the calculations before I asked the navigator to get a fix to confirm, which also took some time, but I thought I accounted for that leg of the journey. I don't have the exact position of the boat displayed, and I'm not sure how accurate the navigator is. Perhaps the actual error was 2-3 arc minutes.

So is this correct? If it is, then my question is about what happens if I had say 4 hr 3 min GMT instead of 5 hr 3 min GMT. I think I would instead start with the GHA table value at 0 GMT, but then how do I account for the extra 3 hours?

1939 Oct. 2; PoD = Kiel; Longitude = 0°
Altitude of Polaris: 56°7.3' at 5 hr 3 min 0 sec GMT

LHA = GHA + SHA + Longitude
= GHA + 322°10.7' + 0°
= GHA - 37°49.3
Time = GMT - 1 = 4 hr 3 min
GHA = 69°58.7' (4 GMT table) + 45.1' (3 min table)
= 70°43.8'
LHA = 70°43.8' - 37°49.3'
= 32°54.5'

Arc minutes altitude correction:
37.3 - (0.4x(54.5/60)) = 36.9

LAT = 56°7.3' - 36.9' = 55°30.4'

Thanks!

[Aktungbby]

CaptBongTrillion! nice 5-year silent run

@CaptBongTrillion, your calculations are absolutely correct. If GMT = 4-03-00, then really "Time" = 3-03-00. Then GHA Aries at 3-00-00 = GHA at 0-00-00 + 45 ° 7.4 '(3 hour GHA increment from the "Increments & corrections" table in the upper left corner.There are also GHA increments for 1 hour (15 ° 2.5 ') and for 2 hours (30 ° 4.9')).

[CaptBongTrillion]

Wow, I don't know how I missed the box in the top left with the hour increments for GHA. I think I started ignoring that box because I thought I didn't need it. Anyways, I did another calculation somewhere near Aberdeen and got a 3 arc minute error in latitude compared to what the navigator said, as expected.

Now if I could get sophisticated enough to determine the ever elusive longitude.

And yes, it has been years since I've played SH5. Computers in the year 2021 might be powerful enough to run SH5

By the way, the maximum navigator error for celestial navigation is automatically set to 8000 m when installing TWoS.

This is me to the fact that it may very well be that you can be more accurate than your default navigator

2-3 arc minutes is the marginal error, which in most cases is smaller.

[les green01]

i try it couple of times couldn't figure it out but it be nice to take a shot and see how snafu my navigator is maybe too much math for me kinda like me trying to figure a intercept path to a convoy or task force