NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

HOME

Re: Moonrise over Connecticut, 19 October 2021
From: Antoine Couëtte
Date: 2021 Oct 29, 12:11 -0700

Frank,

In further reference to my earlier post to which you just replied here, - thanks for your quite detailed reply - let's again take a look at the the USNO Web Application clone following results:

Celestial Navigation Data for 2021 Oct 19 at 21:59:27 UT           
                                                                               
                 For Assumed Position:  Latitude    N 41 18.4                 
                                        Longitude   W 72 30.0                 
                                                                               
                        Almanac Data                |    Altitude Corrections  
 Object       GHA        Dec         Hc       Zn    |   Refr   SD    PA    Sum 
              o   '      o   '      o   '       o   |     '     '     '     '  
 SUN        153 39.1   S10 18.4   - 0 15.2   256.4  |  -31.0  16.1   0.1 -14.8 
 MOON       339 48.3   N 4 02.6   + 0 38.9    85.2  |  -24.0  15.0  55.2  46.2 
 VENUS      106 55.5   S25 40.0   +15 49.0   212.0  |   -3.4   0.0   0.2  -3.2 
 JUPITER     33 22.6   S15 08.8   +22 57.4   138.6  |   -2.3   0.0   0.0  -2.3 
 SATURN      48 53.7   S19 19.7   +25 32.1   155.2  |   -2.0   0.0   0.0  -2.0 
 ARIES      358 27.2                                                           

                 Moon phase is waxing,  99% illuminated.

there is a definite refraction correction error for the Moon which should show -31.0' exactly like for the Sun, instead of currently showing -24.0' .

As earlier surmised, the Moon refraction Correction showing up as " -24.0 " is the Inverse Refraction - actually the right refraction function to be used in such reverse engineering - applied by error to the Geocentric Height "Hc" while it should be applied to the Topocentric unrefracted height.

BODY	Hc	Inverse refraction from Éphémérides Nautiques	Published Refr in USNO Web Application clone
SUN	-0°15.2’	-30.04’	-31.0’
MOON	+0°38.9’	-24.03’	-24.0’
VENUS	+15°49.0’	-3.37’	-3.4’
JUPITER	+22°57.4’	-2.27’	-2.3’
SATURN	+25°32.1’	-2.01’	-2.0’

As earlier surmised, this mismatch is only visible onto Low Alt Bodies with a significant HP, in other words, it is only visible for Lady Moon quite close from the Horizon.

Hence it fully explains why the example you just published shows a perfect match between the former USNO Web Application and the current USNO Web Application clone since Lady Moon height is about 25° in it.

This bug should be very simple and straightforward to correct : simply apply Inv (Ref) to Topocentric Height vs. Geocentric height.

Hope it helps !

Antoine M. "Kermit" Couëtte

antoine.m.couette[at]club-internet.fr

What is NavList?

NavList is a community devoted to the preservation and practice of celestial navigation and other methods of traditional position-finding. We're a group of navigators, navigation enthusiasts and hobbyists, mathematicians and physicists, and historians interested in all aspects of navigation but primarily those techniques which are non-electronic.

To post a message, if you are already signed up as a NavList member, start a new discussion or reply to any posted message and use your posting code (this is a simple low-security password assigned when you join). You may also join by posting. Your first on-topic messsage automatically makes you a member, and a posting code will be assigned and emailed to you for future posts.

Uniquely, the NavList message boards also permit full interaction entirely by email. You can optionally receive individual posts or daily digests by email, and any member can post messages by email (bypassing the web site) by sending to our posting address which is "NavList@NavList.net". This functionality is similar to a traditional Internet mailing list: post by email, read by email, reply by email. Most members will prefer the web interface here for posting and replying to messages.

NavList is more than an online community... more about that another day.

© Copyright notice: please note that the rights to all messages and posts in this discussion group are held by their respective authors. No messages or text or images extracted from messages may be reproduced without the explicit consent of the message author. Email me, Frank Reed, if you have any questions.

Subject:
Author:
Start date:	(yyyymm dd)
End date:	(yyyymm dd)

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

NavList

What is NavList?

Join / Get NavList ID Code

Retrieve a NavList ID Code

Email Settings

Custom Index

Add Images & Files
Name or NavList Code:	Email:

Name:
	(please, no nicknames or handles)
Email:

NavList ID Code: