Celestial Navigation Plugin Redux

[P_Dub]

Well, I have been doing sights as far back as 1958 and it work OK. The only thing I can had is to add a place to enter the DR position and this in order to remove the ambiguity of the position calculated for 2 sights. Otherwise the positioning looks good to me as I did obtain the same result as done by hand and tables. Furthermore I did check with an other program and the results are the same or close. If you need more checking, I may do so during the week coming.
Bye for now.

[rgleason]

Yes, P_Dub, I understand that you know this stuff. Is this newly compiled version working the way you expect??? I bombed twice and get that message using the examples at the bottom of the manual, and we want to be sure it works properly before publishing!!

[rgleason]

P_Dub
Maybe first start with lat long, and put it in "FIX".
Then if you are doing a Sight, you set the Time to your UTC Time, then pick a celestial orb and select FIND, your FIX will show up at the top as LAT and LONG (at the time you put in) Then you have the Altitude and Azimuth for that location and time to quide you with your sights.

[rgleason]

I know that use of Azimuth crashes O now.

[rgleason]

Even thought Celestial Navigation now appears to operate, it is not worrking properly.
1. Use of Azimuth bombs Opencpn very quickly, or ends up thinking and thinking and never completing.
2. Use of Altitude when using UTC at Greenwich does place sightings through Boston!!!
The way I am doing this is to enter a FIX at Boston. Then start a NEW sighting and set the present time to UTC ( use that for all sightings for simplicity) For Boston Present Time - 5 hours = UTC (disregarding daylight savings time). Then I pick a celestial orb that results in a positive Altitude when I hit FIND. If the altitude is above 20 I'll use it,provided I've set the UTC time right and the LAT and LONG that come up are Lat 41 and Long 71.5 and then I close FIND and enter the Altitude value in the field for the Sighting Measurement Degrees ....

I can enter multiple values but the circles do not go through BOSTON!!

What seems to be happening as well is even though the Sighting TIME stays the same, the Altitude changes over 20-30 minutes even though the Sighting TIME has not changed. This is just plain wrong.

Now it is very possible that I am wrong about this, but this plugin is no longer working the way I have known it to work and the way I expect it to work.

I think we need to do more work and checking before releasing it. Not ready for prime time. Unfortunately. I wonder what has changed in trying to make it more accurate?

[stelian]

Originally Posted by rgleason

Even thought Celestial Navigation now appears to operate, it is not worrking properly.
1. Use of Azimuth bombs Opencpn very quickly, or ends up thinking and thinking and never completing.
2. Use of Altitude when using UTC at Greenwich does place sightings through Boston!!!
The way I am doing this is to enter a FIX at Boston. Then start a NEW sighting and set the present time to UTC ( use that for all sightings for simplicity) For Boston Present Time - 5 hours = UTC (disregarding daylight savings time). Then I pick a celestial orb that results in a positive Altitude when I hit FIND. If the altitude is above 20 I'll use it,provided I've set the UTC time right and the LAT and LONG that come up are Lat 41 and Long 71.5 and then I close FIND and enter the Altitude value in the field for the Sighting Measurement Degrees ....

I can enter multiple values but the circles do not go through BOSTON!!

What seems to be happening as well is even though the Sighting TIME stays the same, the Altitude changes over 20-30 minutes even though the Sighting TIME has not changed. This is just plain wrong.

Now it is very possible that I am wrong about this, but this plugin is no longer working the way I have known it to work and the way I expect it to work.

I think we need to do more work and checking before releasing it. Not ready for prime time. Unfortunately. I wonder what has changed in trying to make it more accurate?

Can you give me precise instructions on how to reproduce this two separate bugs ?

It may be because I don't use the plugin the way you do, so I'm not sure what you mean by "entering a fix at Boston", or "Hit FIND"...

If I can reproduce the bugs I might be able to help fixing them.

[stelian]

Originally Posted by rgleason

I kept getting "Warning: Measurement certainly set too small, sight may not appear."

What is your measurement certainly ? Does the message go away if you increase it ?
(the measurement certainly gives the width of the cercle. If the width is too small - ths cercle will not appear)

[P_Dub]

I did not use it that way either, but only calculating the sights and find the positions; Which I suppose, the system was meant for. I will try later on your way.
Have a good day.

Note:- I see nowhere to enter the lat and long prior to working the sights. You probably do not have the same plugin!

[P_Dub]

The only difference I found was the semi-diameter of the sun, which might have given you the difference. Once it is adjusted the result is OK.
Bye

Note:- The interface should have a facility for entering the DR lat and long like I said in one of my message. Otherwise it can lead to confusion.

[stelian]

Originally Posted by stelian

I'm not sure what you mean by "entering a fix at Boston", or "Hit FIND"...

Oh, I never payed attention to that button ! Now I understand what you're doing.

So, I tried creating a new sight, selecting altitude or azimuth, clicked on the "Find" button, entered 47 / -3, this gives the altitude and azimuth of the sun at my current date, then entered that altitude and azimuth in the sight degree/minutes (after decimal to minutes conversion) text boxes.

It does work correctly here (although I can see an error of 5 to 10 miles), it doesn't crash.

But this is on Linux.

If you give me a precise date / altitude or azimuth, I can try to reproduce the crash, first on Linux then on Windows.

[rgleason]

P_dub and Stelian, sorry I should have been more explicit.

I suppose I should go up to the rooftop to use my sextant and learn how to take sights again. But that is not the purpose here. We want to check Celestial_Navigation_pi. So this an armchair method that I think may be ok using the "Find" Button.

(Short Answer to my problem: I think the problem was the default setting of "Clock Offset: -10000 seconds"! This should be set at Default=0 when the plugin is installed! And I guess any new setting should be saved -IMHO)

(Note I have not done this using "Azimuth" values but it should be checked.)

I will try to put this process at the bottom of the plugin Wiki for others to review.
---------------
Process
1. In OpenCPN with Celestial_Nav Enabled.
2. Right Click, Drop a waypoint and
3. Right click on WP, pick Properties set lat 41.35 long -71.10 Boston,Ma
4. Try to Right-click "Move the boat" to that exact location.
5. Check that Clock Offset = "0"
5. In Cel_Nav Pick "New"
6. Time Tab: Boston Time ( UTC-5): Oct 10, 2017, 13:00 so UTC 10/10/17 18:00
7. DR Shift: Distance=0 Bearing=0
8. Config; Set color wanted.
9. Parameters; Eye height=2.0 meters Temp 10 celcius, Pressure=1010 Index Error 0 min. Click set as defaults.

10. Sight Tab: Type=Altitude; Cel Body=Sun; Limb=Lower; then pick "Find"
11. Make sure to change Latitude: 42.35, Longitude to -71.1 (Would very much like to Right Click > Move Boat Lat/Long!)
12. Read Altitude of Sun on 10/10/17 UTC 1800 = 36.888867, Select "Done"
13. Enter "Degrees" 36.888867, make the Minutes 0. Hit OK.
14. Then enter another Type= Altitude CB=Arcturus Limb=Lower, check that the Time, DR Shift, Config are the same. Hit Find.

15. Enter Lat=42.35 Long=-71.1 See Altitude of Arcturus UTC 10/10/17 18000 is 66.507224 Hit Done.
16. Enter Degrees=66.507224, make Minutes=0. Hit OK.
17. Found "Clock Offset"= -10000 or something, set it at "0" then screwed around for awhile checking other things. Sights changed position, better...

18. Then enter another Type= Altitude CB=Kochab Limb=Lower, check that the Time, DR Shift, Config are the same. Hit Find.
19. Enter Lat=42.35 Long=-71.1 See Altitude of Kochab UTC 10/10/17 18000 is 58.133196 Hit Done.
20. Enter Degrees=58.133196, make Minutes=0. Hit OK.
21. Then find Fix. The fix is 41 nm off. To many circles east to west.

22. Pick "New" and set Alkiaid. Check all Tabs set correctly. Pick "Find"
23. Enter Lat=42.35 Long=-71.1 See Altitude of Alkaid UTC 10/10/17 18000 is 80.397926 Hit Done.
24. Hit Fix new red X draw and it is 31 nm away. Better.
25. Turn off the Sun sighting with the "eye". Better.
26. Hit Fix new red X drawn and it is 8nm away.
-------
Simplification: Parameters that are always the same:
Clock Offset =0
Time: Boston Time ( UTC-5): Oct 10, 2017, 13:00 so UTC 10/10/17 18:00
DR Shift: Distance=0 Bearing=0
Parameters: Eye height=2.0 m Temp 10 c, Pressure=1010, Index Error 0 min
Latitude: 42.35, Longitude to -71.1
-----
Using "Find" and Altitude set for the Star and enter the Lat/Long above:
Star - Altitude Entered
Alkaid 80.397926
Kochab 58.133196
Arcturus 66.507224
Sun 36.888867

[rgleason]

Here are the rest of the sequence.

[stelian]

I didn't yet tried to reproduce your entire sequence, but if I understand correctly, the "only" problem is a 10 mile distance between the fix and the real target ?

If this is the case, then I already seen the same problem, see my mail above.

I thought that you had crashes and infinite calculations ?

[stelian]

Ok, reproduced your sequence.

Comments:
- you have some obvious errors in your message, when you enter the coordinates of the WP, you should enter 42.35/-71.10 (and not 41.35). Moreover, I think the WP dialog only accepts the degrees/minutes format, so you should enter 42° 21'N and 71°06'W.

- i do not have the 'clock offset' problem here on linux. The contents of the clock offset is always 0.

- the results seem even worse here, see screenshot (I have reduced the minutes certainity to 1 minute): 52 miles off the target.

[P_Dub]

I think that you have the wrong Sights altitude entered. After checking with other sight I am arriving with the correct result as calculated by an other program. So their is no reason why you get this. Check your value with the time set correctly.
Bye