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» Online Classroom   »   » Public Discussion of Cel Nav   » GHA between moon, and star when angle gets >180

   
Author Topic: GHA between moon, and star when angle gets >180
navi


 - posted December 15, 2017 04:01 PM      Profile for navi           Edit/Delete Post 
Hi,

I believe I am doingthe right thing justlooking for a confirmations.

So on UTC 6 Dec 2017 I calculate Moon to Betelgeuse GHA difference at 03:00:00 and get
31d 3.2'- 9d 44.8' = 21d 18.4'

At 04:00:00 I do the same and get
46d 5.7'-24d 7.6'=21d 58.1'

All good!

24 hours later I want to do the same thing!

Then however GHA moon is 355d 9.3' and Betelguese GHA is 32d 2.4

What I now do is:

03:00:00 UTC 7 Dec
360d-(355d 9.3' - 32d2.4')= 36d 53.1'

04:00:00
47d 4.9' -9d 33.7'=37d 31.2'

About 0.5 d difference which seems to make sense.

Is my 360d-(355d 9.3' - 32d2.4')= 36d 53.1' the right thing to do when that difference is >180 degrees?

From: Chi
David Burch


 - posted December 15, 2017 04:48 PM      Profile for David Burch           Edit/Delete Post 
I think this is not a good lunar star. May i please recommend that you check this site

http://reednavigation.com/lunars/lunars_pre_v5.html

to find a good lunar star and then work those. Also that site then tells you the right solution to the lunar. So you can practice that way.

If a star is not in line with the moon's motion you will not get good lunar results. So making those choices properly first is the most important step... rather than tracking down math steps that will not likely be fruitful.

in passing, if needed you can draw a circle and mark the angles on the circle to help figure out the subtractions.

From: Starpath, Seattle, WA


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