A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2017 Sep 30, 00:05 -0700
RE : Hirose-sep-2017-g40222
Thank you for your very clear and most interesting reply.
As regards "deltaT values" I have been using the polynomial values published here https://eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html .
These deltaT values are not super accurate for our contemporary period, but they relieve you from having to search real values each time from the Web. They are sufficiently close for many centuries - in the past and hopefully into future - for "classical" Celestial Navigation and Lunars applications since in 1 second of time the Moon RA changes only by 0.5 " . And anyway I can change them any time at a finger tip including during computations.
Although the +70.4 s value is unrealistic - since UT1-UTC would then exceed 1 second of time, thanks for your brilliant demonstration - we all agree that it has absolutely no appreciable consequence on the final result in the case of a Lunar, (see above).
Your trick to use MICA with any deltaT value is also quite interesting. Thanks for sharing it with all of us.
In order to best compare my own results with yours, I have therefore computed them again with TT-UT1 = + 69.482 s .
I am getting a refracted distance is 3.045' to be compared to your Lunar 4 refracted value of 0.05124° ( 3.074' ) . Sigh of relief :-)
It is now fully confirmed that the NavList web based Lunar application ( http://reednavigation.com/lunars/lunars_v4.html ) should desirably be enhanced - through an hopefully "easy" software fine-tuning involving iterations as earlier demonstrated - in order to 100% reliably tackle short distance Lunars (below e.g. 5°) down to 0° distance occultations.
Let us then wait for feedback from other NavList Members, and in particular from Frank.
Thanks to you again for your contribution, and
Best Friendly Regards,