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Sean C wrote:
> I am trying to approximate, as closely as possible with the formulas found 
in the N.A., what would be the *apparent* altitude of the bodies at the time 
of the lunar. I've been shooting from my front yard at night, so no natural 
horizon. I am currently experimenting with coffee and soon, motor oil as an 
AH. Until then, I must calculate the altitudes. The way I see it, there are 
basically three ways I can use the equations given on your lunars page: Use 
the directly calculated altitude for H_Moon OR use Hc to calculate PA & 
refraction and subtract those from Hc to approximate Ha OR use the method I 
outlined in my previous post to more closely approximate PA, refraction & Ha. 
Conveniently, ICE gives all of the corrections alongside the Hc. But, as 
you've pointed out, it's getting increasingly inaccurate, especially 
regarding the Moon. Besides, I wanted to try out MICA!

I'm unsure of your overall objective. However, if you need simulated
observed altitudes, my Lunar3 program will generate those. Or if you
want the calculated lunar distance between specified limbs at a given
time and position, it will do that. Or it will solve for time, given a
lunar distance from a known location. The program runs on Windows and is
free:

http://home.earthlink.net/~s543t-24dst/lunar3/index.html

The "Test Results" link on that page is a fully worked tutorial on
creating, by hand, synthetic lunar distance observations with either JPL
HORIZONS or USNO MICA. These observations were the basis for validating
Lunar3's accuracy.

Regarding ICE, the delta T of this old program has become excessive,
with some impact on Moon coordinates. However, with corrections to UT1
and longitude, ICE can be made to "work like new." The trick also works
on old versions of MICA, which also suffer from excessive delta T,
though not to the same extent. The "Star Lunar with USNO MICA 2.0" at
the above site describes the method in a single paragraph.


> So, as an example, I'll use a lunar I shot on March 24th of this year (2014). Here's the raw data:
>
> 2014 Mar. 24
> Moon-Venus Lunar (Near Limb)
> AP: N 37° 03..3', W 076° 28.6'
> Altitude: 40 ft.
> Temp.: 30.5 °F
> Press.: 30.30 inHg
> Watch Error: 0
> Index Error: 0
>
> (Note: I ignored the temp./press. correction for this exercise.)
>
> UTC: 11h 12m 27s
> LDs: 38°01.8'


With those parameters, Lunar3 gives these predicted angles:

Moon:
  33°38.24′ computed unrefracted center altitude
    -16.27′ unrefracted semidiameter
      1.54′ refraction
  33°23.51′ refracted lower limb altitude
173°16.28′ predicted azimuth

Venus:
  23°17.69′ computed unrefracted center altitude
      2.35′ refraction
  23°20.04′ refracted center altitude
130°58.15′ predicted azimuth

predicted Moon to Venus angle:
   38°18.81′ center to center, unrefracted
       0.89′ refraction
   38°17.92′ center to center, refracted
      16.26′ Moon near limb refracted SD

   38°01.80′ observed angle
   38°01.65′ computed Moon to Venus
    0°00.15′ observed - computed


Its time solution is 11:12:01.48 UTC. You gave the actual time of sight
as 11:12:27.

I assumed you shot the center of Venus. However, its phase angle was
almost exactly 90°, so Venus was half illuminated. Its semidiameter was
.20'. Because Lunar3 has no provision for observing the center of light,
only the center of a body or either limb, its recommendation was to
shoot the far limb of Venus against the near Moon limb. That was based
on its analysis of the illimination angles of both bodies.

If that's what you actually did, it would account for nearly all the
excess observed distance. In that case, the time solution is only ten
seconds late compared to the true observation time you recorded.

--

   

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