Sight Reduction Tables C-S Line

[Sailingsailor12]

Will somebody please explain to me the significance of the C-S line on the right hand page of the sight reduction tables (declination contrary to latitude) and why when crossing the line, the direction goes from N to 180 - N. Thank you.

Sincerely,
Mark Rehwaldt
DeerWood9323@Yahoo.com
(307) 761-1814

[wsmurdoch]

Z is calculated from the arccos of a number that is a function of the Hc, dec, and lat. The arccos of a number can represent either of two angles between 0 and 360 degrees. The choice of which one is correct must be made based on the LHA.

For example: cos(45 degrees)=0.707 and cos(315 degrees)=0.707, but if your calculator is asked for arccos(0.707) it will only say 45 degrees even though it could also be 315 degrees. You have to choose the correct answer. The LHA points you in the correct direction, either east of you or west of you.

I hope I got this right. It's been a while.

Bill

[Sailingsailor12]

Bill: Thank you. Mark R.

[SeanPatrick]

You can also think of the contrary/same line as the horizon.



Since the declination is listed in ascending order from zero, the first line has the body just on the other side of the equator from you. As you move down the page, the body moves further from your hemisphere and so (at the given LHA) will eventually have an altitude of zero. There is really no point in calculating further for sight reduction purposes.


The figures below the line are for declinations in the same hemisphere, but for reciprocal LHAs (hence the azimuth shift). These altitudes also diminish to zero (the horizon) at the c/s line. However, they ascend as you move down the page because they are approaching your elevated pole.

[jmschmidt]

Don't know but with the GPS equipment on the airplanes I flew, if you punched in "N POLE" it would produce a compass heading and distance to the North Pole. If on autopilot if you hit EXECUTE it would turn to the heading and fly to the North Pole, or until you ran out of fuel.

If you punched in "S POLE" in would not produce a heading or distance to the South Pole.

Could be something similar with software on your equipment

[Sailingsailor12]

Originally Posted by SeanPatrick

You can also think of the contrary/same line as the horizon.



Since the declination is listed in ascending order from zero, the first line has the body just on the other side of the equator from you. As you move down the page, the body moves further from your hemisphere and so (at the given LHA) will eventually have an altitude of zero. There is really no point in calculating further for sight reduction purposes.


The figures below the line are for declinations in the same hemisphere, but for reciprocal LHAs (hence the azimuth shift). These altitudes also diminish to zero (the horizon) at the c/s line. However, they ascend as you move down the page because they are approaching your elevated pole.

Sean Patrick: Thank you. Mark R.

[Sailingsailor12]

Sean Patrick: Thank you. Mark R.

[Sailingsailor12]

Thank you. Mark R.

[SeanPatrick]

Originally Posted by Sailingsailor12

Sean Patrick: Thank you. Mark R.

You're welcome! If you have any other questions, I'd be happy to help.


Also: check out NavList for more information on celestial than you can shake a stick at. (I'm "Sean C." over there.)


Cheers!

[Adelie]

Originally Posted by SeanPatrick

......
These altitudes also diminish to zero (the horizon) at the c/s line. However, they ascend as you move down the page because they are approaching your elevated pole.

The 229 has results to a bit below 0deg and 249 has results down to around -6deg.

229 does this to account for bodies shot at the horizon where refraction is very large.

249 goes even further below the horizon because of refraction and because it is meant for aircraft use and height of eye can be up to 50,000ft or so.