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» Online Classroom   » Celestial Navigation   » Public Discussion of Cel Nav   » Weird question - LOP from Polaris?

Author Topic: Weird question - LOP from Polaris?

 - posted June 08, 2020 10:15 AM      Profile for bruce           Edit/Delete Post 
I was doing a latitude with Polaris the other day, and just for grins I put the Ha and WT into the sight-reduction program on my calculator (an HP-41 with the nav pack).

I was expecting it to ignore me, or throw an error or something. Instead, it gave me an Azimuth and Intercept.

I can't find any part of the Nautical Almanac where I could get the info I'd need to produce a reduction for Polaris. I know I can get an Azimuth from the Polaris tables, but I can't find a way to get a GHA for Polaris, and without the GHA I can't compute the LHA I need to look up Hc-tab in the tables. So I'm not sure how to reasonably reduce a sight for Polaris with the normal process(es) to end up with an LOP.

I'm guessing that because Polaris is pretty much always at "my" meridian, its LHA is really close to my DR-Lon, and so it might be really hard to use....the azimuth will always be at or near 000, so I'm thinking that it essentially ends up being just a latitude anyway.

But it got me wondering... is that computed solution meaningful (and, more to the point, is it a valid LOP?) And, if so, is there a way to compute it manually?


From: Everett, WA
David Burch

 - posted June 08, 2020 10:47 AM      Profile for David Burch           Edit/Delete Post 
Polaris is listed in the star list at the back of the almanac. It has SHA about 315º. Get SHA there and then use GHA Aries from daily pages to get GHA.
From: Starpath, Seattle, WA

 - posted June 08, 2020 11:40 AM      Profile for bruce           Edit/Delete Post 
Ah! Thanks, I didn't think to look there.

So that the other question.... does a reduction of Polaris provide any useful LON info, or is it basically still a Latitude?

From: Everett, WA

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