NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Heliacal rising - definition?
From: Marcel Tschudin
Date: 2011 Aug 18, 23:25 +0300
From: Marcel Tschudin
Date: 2011 Aug 18, 23:25 +0300
Good evening George,
I'm happy to see that you are in a position to contribute again to NavList..
I made this literature search over 10 years ago. Presently this subject is not in my focus. I will make a note to look also what he contributed on this subject once I return back on it.
I wish you all the best George; keep strong!.
Marcel
I'm happy to see that you are in a position to contribute again to NavList..
I made this literature search over 10 years ago. Presently this subject is not in my focus. I will make a note to look also what he contributed on this subject once I return back on it.
I wish you all the best George; keep strong!.
Marcel
On Thu, Aug 18, 2011 at 11:07 PM, George Huxtable <george@hux.me.uk> wrote:
I'm surprised that nobody has mentioned Brad Schaefer's work in this
context (and in many other related fields concerned with atmospheric
effects on arriving light).
A search for Schaefer, combined with extinction, should take you to
anything you need to know.
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: "Apache Runner" <apacherunner@gmail.com>
To: <NavList@fer3.com>
Sent: Wednesday, August 17, 2011 4:44 PM
Subject: [NavList] Heliacal rising - definition?
|I have a question: can someone define heliacal rising in a quantitative
| fashion? The reason I ask is that I'm interested in writing a piece of
| code to identify heliacal risings, but when I think about the
| implementation, many questions arise.
|
| Roughly speaking, the heliacal rising is the first time a star is visible
| just before sunrise. If I think about what might actually be visible
at a
| given latitude, this seems to me to depend on the magnitude of the star,
and
| even atmospheric effects, and even the height of the observer, if I were
to
| get persnickety.
|
| On the other hand, if I define some group of stars with a magnitude
greater
| than X, and say it's 'first visible' before local sunrise at, say 6
degrees
| above the horizon at the start of astronomical twilight, I can get a
precise
| definition that I could implement in a piece of code - although this
would
| probably yield some stars that would be several days past the 'first'
| observation.
|
| The latter definition is straightforward to implement, while the former
is
| difficult for me to see how it would work.
|
| Any thoughts?
|