NavList:

   

Reply

Brad couldn't make sense of the formula I provided. Which was fair enough;
it made no sense, because on the right-hand side, I had written d when it
should have been D. Sorry for that carelessness.

It's effectively Young's method, but worked backwards, to obtain d from D,
instead of the other way round, as it would be when used in finding a true
angular distance, such as a lunar distance, from an observation.

It's exactly as Brad deduced-

"After carefully examining your post, I can (hopefully) describe the terms
H1 is the true altitude of object 1, should refraction not exist
H2 is the true altitude of object 2, should refraction not exist
h1 will be the observed altitude of object 1, when refraction is present
h2 will be the observed altitude of object 2, when refraction is present.
d is the observed distance, when refraction is present.
D would be the true distance, should refraction not exist.  D is not present
in the equation above

Should the equation read?
cos d = (cos D +cos (H1 + H2)) cos h1 cos h2/(cosH1cosH2) -cos (h1+h2)"

Yes, it should.

"I am also having a bit of problems properly grouping the terms.  Is it
term1  = (cos D + cos(H1+H2))
term 2 = cos h1 * cos h2
term 3 = cos H1 *cos H2
term 4 = cos (h1+h2)
cos d = term1 * term2 / term3 - term4
that seems to yield a term which I cannot take the arc-cosine of."

I don't follow that. Presumably, h1 is nearly equal to H1, and h2 is nearly
equal to H2. In which case, the multiplier term
cos h1 cos h2/(cosH1cosH2) won't differ much from 1.

So the right hand side won't differ much from-
(cos D +cos (H1 + H2)) - cos (h1+h2), which will be nearly cosD.
So, d will be near acs(cosD), which implies that d and D will differ little,
as they should.

In fact, if Brad puts h1=H1, and h2=H2; that is, zero refraction, then d
should exactly equal D. If not, something is wrong.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
----- Original Message -----
From: "Brad Morris" 
To: 
Sent: Wednesday, March 10, 2010 4:19 PM
Subject: [NavList] Re: Star - Star Observations


| George, you wrote:
| cos d = (cos d +cos (H1 + H2)) cos h1 cos h2/(cosH1cosH2) -cos (h1+h2)
|
| After carefully examining your post, I can (hopefully) describe the terms
| H1 is the true altitude of object 1, should refraction not exist
| H2 is the true altitude of object 2, should refraction not exist
| h1 will be the observed altitude of object 1, when refraction is present
| h2 will be the observed altitude of object 2, when refraction is present.
| d is the observed distance, when refraction is present.
| D would be the true distance, should refraction not exist.  D is not
present in the equation above
|
| Should the equation read?
| cos d = (cos D +cos (H1 + H2)) cos h1 cos h2/(cosH1cosH2) -cos (h1+h2)
|
| I am also having a bit of problems properly grouping the terms.  Is it
| term1  = (cos D + cos(H1+H2))
| term 2 = cos h1 * cos h2
| term 3 = cos H1 *cos H2
| term 4 = cos (h1+h2)
| cos d = term1 * term2 / term3 - term4
| that seems to yield a term which I cannot take the arc-cosine of.
|
| Help!!!!
|
| Best Regards
| Brad
|
|
| "Confidentiality and Privilege Notice
| The information transmitted by this electronic mail (and any attachments)
is being sent by or on behalf of Tactronics; it is intended for the
exclusive use of the addressee named above and may constitute information
that is privileged or confidential or otherwise legally exempt from
disclosure. If you are not the addressee or an employee or agent responsible
for delivering this message to same, you are not authorized to retain, read,
copy or disseminate this electronic mail (or any attachments) or any part
thereof. If you have received this electronic mail (and any attachments) in
error, please call us immediately and send written confirmation that same
has been deleted from your system. Thank you."
|

   

Reply