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Bill,
as no one else seems to be interested,
if you can wait till next week,
I will just hand you the formula on a sheet of paper
rather than type it in e-mail.
(I suppose your computer has no TeX installed.
TeX is a special soft for typing formulas,
used by mathematicians).
Alex.

On Mon, 14 Mar 2005, Bill wrote:

> Alex
>
> > 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?
>
> We verified that your operating system (free linux flavor of unix if I
> recall) and box could read a hybrid Mac/PC CD burned on a Mac (OS 9.x), and
> that your Gnumeric application opened the Mac Excel spreadsheet without
> complaining, and did not choke on all the "IF" arguments in my spreadsheet.
> It appeared to handle all the calculations flawlessly.  Note I use absolute
> values for declination, latitude, longitude etc. and let IF arguments pick
> the correctly signed value/cell based on input of North, South, East, West,
> v & d incremental correction by body, etc. Only v & d values are signed on
> entry. It also calculates Zn from Z with IF arguments.  I did not play with
> changing the N, S, E, W inputs on your box to see if your program would
> honor the IF statements if parameters were changed.  I don't know whether
> you played with the provided CD to determine if it would work across the
> board.
>
> We have not tested to determine if my Mac will read a CD from your machine,
> or if Excel will open your Gnumeric files with or without translation.
>
> If I recall, several of the of the list members use both Mac and PC
> platforms.  Any input as to the application and platform compatibility would
> be appreciated by me.
>
> > 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.
>
> Would like to try both your Gnumeric files and have the formula.  If others
> request, go ahead and post.  Otherwise we can exchange over adult beverages
> when you return from the Great White North and I return your copy of Meesus
> etc. (before it does further damage to my aging gray matter and gets me
> invitations to  from the list ;-)
> >
> > (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.
>
> Understood.  Working towards understanding how, as you have surmised.
>
> Thanks
>
> Bill
> >
> >
> > 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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