NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: An azimuth nomogram: what's under the hood?
From: Stan K
Date: 2018 Mar 13, 18:57 -0400
From: Stan K
Date: 2018 Mar 13, 18:57 -0400
FWIW, Celestial Tools Sight Planner tool shows the azimuths of sunrise, sunset, moonrise, and moonset, for a given date, latitude, and longitude. There is a choice of whether to display the azimuth when either the upper limb or the center is on the visible horizon.
Bruce - I just came in from working on my driveway. Apparently it was pretty warms when the snow started, so the first two inches are pretty much slush, a real heavy mess, but the rest is wet snow, not light and fluffy. I actually think the last snow was "better".
Stan (central Connecticut)
-----Original Message-----
From: Bruce J. Pennino <NoReply_Pennino@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Tue, 13 Mar 2018 12:08
Subject: [NavList] Re: An azimuth nomogram: what's under the hood?
From: Bruce J. Pennino <NoReply_Pennino@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Tue, 13 Mar 2018 12:08
Subject: [NavList] Re: An azimuth nomogram: what's under the hood?
Hello:
This nomograph is very interesting. I’ve done this calculation before
never recognizing that it was a parabola .Here in New England (where we are
having our third Nor’easter in 11 days) many of us buy “Eldridge”.
Eldridge has a handy – dandy table in the back where for a specific date and
latitude the azimuth of sunrise and sunset is quickly obtained. I
recollect that Mixter also has a similar table. When it really matters,
check you compass everyday.
Why is the declination of sun go to ninety degrees? What have I
missed?
The good news, this snow is light and fluffy, the last storm was shoveling
16 inches of wet mashed potatoes.
Regards,
Bruce
From: Tony Oz
Sent: Tuesday, March 13, 2018 8:45 AM
Subject: [NavList] Re: An azimuth nomogram: what's under the
hood?
Dear Sean and Gary,
Thank you for the feedback.
I should have made the translation myself. The nomogram is called
"A celestial body's rise and set semi-circular true
azimuth".
The left wing of the parabola has the "Latitude of
observer" label, the vertical scale has the
"Declination of celestial body", the right parabola's
wind has the "Rise (set) azimuth if same-name φ and δ"
label on the inner side and the "Rise (set) azimuth if contrary-name
φ and δ" label on the outer side.
The comment below the nomogram is "When observing from the sea
level - the center of the celestial body is on the plane of horizon if: - Sun's
lower limb is over the horizon at 0,7 of its diameter; - Moon's upper limb is at
altitude ~0°; a star or a planet is at 0,5° altitude
(a Sun's diameter)".
The rest of the text is translated correctly.
So, back to my initial questions.
I wonder why the nomogram is based on the parabola?
I wonder how could I re-calculate positions of each and every angular
mark along each scale?
Regards,
Tony
