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Bill,
You are welcome to use my script for this.
I think we checked that my Gnumeric script
works with your Excel, or did we verify vise versa?
Or you want the relevant trig
formulas, to program them yourself?
They are easy and I can post them (if there are other
interested people) or email them to you directly.

(I believe these formulas are also in Chauvenet, but
cannot check now because I am in Canada, coming back
in a week.

On your other question: BOTH star altitudes have to be corrected
for refraction.

A


On Fri, 11 Mar 2005, Bill wrote:

> Meesus et al gave formulas for calculating star-to-star angular distance
> given declinations and SHAs.
>
> I am looking at the reverse case.  Measuring the angular difference between
> two stars at different altitudes.
>
> For discussion purposes only, I suggest the following theoretical example:
>
> Star 1 Hs (altitude)   50d
> Star 2 Hs (altitude)   10d
> Measured distance      56d 34'.1
>
> Given STP and 0 dip and IC, and adjusting for vertical refraction:
>
> Star 1 Ho              49d 59'.2
> Star 2 Ho              09d 54'.7
> Angular distance        ?
>
> The vertical component of the difference between the two has gone from 40d
> to 40d 04'.5.  Now the distance measured along the Hs diagonal will be less
> than the distance between the Ho positions in the above example (ignoring
> other factors).
> Correct?
>
> My next query, will there be horizontal refraction as well?
>
> In Meesus's chapter on refraction he gives an example of the reduction of
> the Sun's vertical observed measurement when near the horizon due to
> refraction.  He then states, "...the horizontal diameter of the solar disk
> is very slightly contracted by reason of the refraction.  This is due to the
> fact that the extremities of this diameter are raised along vertical circles
> that meet at the zenith."  He goes on to mention Danjon, "...writes the
> apparent contraction of horizontal diameter of the Sun is practically
> constant and independent of altitude, and  that this contraction is
> approximately 0".6."
>
> Perhaps I am comparing apples to oranges, but the star viewed through the
> horizon glass is straight on and would not exhibit horizontal refraction?
> As the other star is viewed at an angle (relative to the first) through the
> index and horizon mirrors, would there be horizontal refraction affecting
> the horizontal component of the diagonal between the two?  If so, how would
> that correction be calculated?
>
> Confused in Indiana
>
> Bill
>

   

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