Something wrong with the PDF tables

Murray Peake — Fri, 21 Oct 2016 07:20:24 -0000

Hi Lars,

Glad to be of help. The tables look pretty good now.

Best Regards

Murray

Something wrong with the PDF tables

Lars — Thu, 20 Oct 2016 21:11:07 -0000

Hi Murray,

wow, thanks for debugging the script. I have not looked into this for a while. Unfortunately I am busy with another project but I fixed the script according to your suggestions. The rest seems to work. There are some other places were the epoch is set - I wonder if those are incorrect as well.

I will upload a new version.

Best regards,

Lars

Something wrong with the PDF tables

Murray Peake — Fri, 14 Oct 2016 19:32:46 -0000

Setting the epoch and date with
temp_observer.epoch = ephem.date((self.epoch, 0))
temp_observer.date = ephem.date((self.epoch, 0))

    and 
    observer.epoch = ephem.date((self.epoch, 0))
    observer.date = ephem.date((self.epoch, 0))

    gives Hc within a minute or so of the 1975 almanac with epoch set to 1975.

    Hopefully everything else still works...

    Thanks Lars for this project.

    Best Wishes
    Murray

Something wrong with the PDF tables

Murray Peake — Fri, 14 Oct 2016 19:10:18 -0000

The rest of the issue seems to be due to date and epoch. To replicate the 1975 HO 249 I forced the date and epoch around line 443
temp_observer.epoch = ephem.date((1975, 6))
temp_observer.date = ephem.date((1975, 6))

 and also around line 489
 observer.epoch = ephem.date((1975, 6))
 observer.date = ephem.date((1975, 6))

 Previously the epoch and date were set to some time in 1905.
 Cheers
 Murray

Something wrong with the PDF tables

Murray Peake — Fri, 14 Oct 2016 18:27:10 -0000

Hi Lars,

Most of the problem seems to be a missing line of code around line 484 which I believe should be
observer.lat=lat*pi/180

This corrects much of the discrepancy - I seem to have a few minutes in Hc to account for yet,
Best Regards
Murray

Something wrong with the PDF tables

Murray Peake — Fri, 14 Oct 2016 15:02:49 -0000

Hi Lars,

I have a few bubble sextants but no plane :-)
I have been comparing the PDF with the 1975 HO 249 Vol 1 and the Hc and Zn values for stars don't match, For Latitude 89 N and LHA Aries 180, Acrux is listed as one of the seven stars. Acrux has a declination of around 63 degrees south, so I think about 62 degrees below the horizon. Do you have any comments? I would like to have this working so will look further.

Best Regards
Murray

Anyone actually using it?

Lars — Fri, 05 Feb 2016 07:29:04 -0000

Hi James,

in a bubble sextant you have a small bubble as an artificial horizont. You put the bubble over the star (and then need to do some calculations as the bubble acts in respones to i.e. the coriolis force).

Regards

Lars

Anyone actually using it?

James Vernon — Sun, 17 Jan 2016 18:42:47 -0000

Hi Lars, I came across your program whilst browsing for
a python celestial navigation library. It looks interesting - thanks for posting it. How does the bubble sextant differ to a standard marine sextant? regards, James.

Anyone actually using it?

Lars — Sat, 21 Mar 2015 15:50:53 -0000

Hi,

it would be interesting to know if this software is of any use to someone.
Feel free to post.

Regards

Lars

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