We all have seen the nice moon HP tables provided by NAUTICAL ALMANAC website, but I wonder if you know that there are two versions... the second of which I can't make heads or tails.
The copy of the Almanac moon HP table - the one with separate lists for upper and lower limbs - makes good sense once you get used to it. However, there is another version tacked on the end of the Sun/Star/planet increment download that boggles the mind. Not only are the numbers incomparable with the Almanac HP table, but there are no upper and lower HP divisions - only a single number. That single number does not compare to UL or LL corrections noted in the Almanac version.
On the same page with the errant HP table is a Refraction table that I like to use with Gunter shots, and the DIP table seems sound, but that HP table gives me the willies... Until someone can tell me how to use it so the numbers match the Almanac version Im not going near it.
joe
The table isn't errant but does require the following;
Total Moon Altitude Correction=
Add SD (semi-diameter) if LL (Lower Limb) shot.
Subtract SD (semi-diameter) if LL (Upper Limb) shot.
Subtract refraction
Add Parallax correction for the HP table provided at the end of Increments & Corrections (found on this site).
That'll make it clearer for you.
Ed
(07-11-2018, 10:37 AM)EdCa Wrote: [ -> ]The table isn't errant but does require the following;
Total Moon Altitude Correction=
Add SD (semi-diameter) if LL (Lower Limb) shot.
Subtract SD (semi-diameter) if LL (Upper Limb) shot.
Subtract refraction
Add Parallax correction for the HP table provided at the end of Increments & Corrections (found on this site).
That'll make it clearer for you.
Ed
Thanks Ed.... now that's something I can sink my teeth into... something to chew on tomorrow... Gracias
joe
(07-11-2018, 11:03 AM)pabrides Wrote: [ -> ] (07-11-2018, 10:37 AM)EdCa Wrote: [ -> ]The table isn't errant but does require the following;
Total Moon Altitude Correction=
Add SD (semi-diameter) if LL (Lower Limb) shot.
Subtract SD (semi-diameter) if LL (Upper Limb) shot.
Subtract refraction
Add Parallax correction for the HP table provided at the end of Increments & Corrections (found on this site).
That'll make it clearer for you.
Ed
Thanks Ed.... now that's something I can sink my teeth into... something to chew on tomorrow... Gracias
joe
OK, Ed, I stand corrected !!! The second HP table is NOT errant. Never let it be said that Joe isnt sometimes humbled. I always tell my wife that I may not always be right - but I'm never wrong :) Can you see the tongue in my cheek?
I chewed on a sample moon shot and found both table answers exactly the same... Its curious that I havent seen the second table instructions... That table adds some excitement to the reduction process... The more steps there are the more opportunity for errors - so when a reduction works out ok one feels great that all that hard work lead to something fairly accurate. However, to be clear, using the second HP table, the one without UL and LL division, the UL -30 correction is of no use?
thanks
Joe
[quote pid='574' dateline='1531367588']
OK, Ed, I stand corrected !!! The second HP table is NOT errant.
I chewed on a sample moon shot and found both table answers exactly the same... Its curious that I havent seen the second table instructions... That table adds some excitement to the reduction process... The more steps there are the more opportunity for errors - so when a reduction works out ok one feels great that all that hard work lead to something fairly accurate. However, to be clear, using the second HP table, the one without UL and LL division, the UL -30 correction is of no use?
thanks
Joe
[/quote]
Joe,
What UL -30 are you referring to? 'Don't know where that is.
Are you referring to the UL subtraction of SD (semi-diameter)?
Ed
(07-14-2018, 09:01 PM)EdCa Wrote: [ -> ][quote pid='574' dateline='1531367588']
OK, Ed, I stand corrected !!! The second HP table is NOT errant.
I chewed on a sample moon shot and found both table answers exactly the same... Its curious that I havent seen the second table instructions... That table adds some excitement to the reduction process... The more steps there are the more opportunity for errors - so when a reduction works out ok one feels great that all that hard work lead to something fairly accurate. However, to be clear, using the second HP table, the one without UL and LL division, the UL -30 correction is of no use?
thanks
Joe
Joe,
What UL -30 are you referring to? 'Don't know where that is.
Are you referring to the UL subtraction of SD (semi-diameter)?
Ed
[/quote]
Ed, this should make it clear; here is an excerpt from Bowditch.. Note second paragraph.
"
Horizontal Parallax Correction: This correction is unique
to reducing Moon sights. Obtain the H.P. correction value from
the daily pages of the Almanac. Enter the H.P correction table at
the back of the Almanac with this value. The H.P correction is a
function of the limb of the Moon used (upper or lower), the ap
parent altitude, and the H.P. correction factor. The H.P.
correction is always added to the apparent altitude.
Moon Upper Limb Correction: Enter -30' for this
correction if the sight was of the upper limb of the Moon.
Correction to Apparent Altitude: Sum the altitude
correction, ... , ... , the horizontal parallax correction, and the
Moon’s upper limb correction. Be careful to determine and carry
the algebraic sign of the corrections and their sum correctly.
Enter this sum as the correction to the apparent altitude.
Observed Altitude: Apply the Correction to Apparent
Altitude algebraically to the apparent altitude. The result is the
observed altitude."
And here is the example they give:
">
Body Moon (UL)
Index Correction 0.0'
Dip (18 feet) -4.1'
Sum -4.1'
Sextant Altitude (hs) 26° 06.7'
Apparent Altitude (ha) 26° 02.6'
Altitude Correction +60.5'
Additional Correction 0.0'
Horizontal Parallax (58.4) +4.0'
Moon Upper Limb Correction -30.0'
Correction to ha +34.5'
Observed Altitude (ho) 26° 37.1'
Also the instructions with the first Moon correction table refers to the -30 upper limb correction.
joe