NavList:

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

HOME

Re: USNO web app cloned
From: Frank Reed
Date: 2020 Sep 15, 18:56 -0700

Eric Fernandez, you wrote:
"It looks really nice! "

Glad you like my clone.

You also wrote:
"Sometimes the Sum of corrections does not match individual correction values, I suppose this is caused by rounding, although the internal precision is higher than 1/10th of [minute]."

Right. It's just rounding. 0.1+0.1 can add up to 0.1. How? If the first number is "really" 0.06 displayed as 0.1 by rounding and the second number is 0.07 also displayed as 0.1, the sum would be 0.13 which rounds down to 0.1. And so on...

You asked:
"One question about refraction correction: close to Hc=0 I get quite different value. They match starting from 5 to 10 degrees. Which formula did you use for it please?"

What formula (or class of formula) do you think we should be using? Let me remind you and everyone else reading along that I designed this USNO clone to be a nearly exact duplicate of the features of the original USNO app, including some small flaws. I did not design it to be a better mousetrap. If I am reading your question right, you may well have noticed one of those flaws or peculiarities. But is it really a flaw? That depends on the intended purpose of those numbers. The corrections are clearly not intended for reducing actual sextant sights. You wouldn't go to this app to work up a sight. So what are they for?? By the way, you can also question the values for the Moon's parallax in altitude. Do they make sense to you? A question for you and anyone else following along: if the Moon's HP is 56.5' (as an example), and we have calculated its altitude (Hc) as 45°00' exactly, then what is its parallax in altitude? Are there two options? Do they both make sense?

Frank Reed

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: