A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2019 Sep 23, 21:53 -0700
"Does anyone recognize the output style of this data, with some degree of certainty, from another USNO software package?"
Yes, of course. It's the same output as the old ICE (Interactive Computer Ephemeris) program - the precursor to MICA (Multi-year Interactive Computer Ephemeris). I still have the former on my laptop, but I haven't run it in quite some time. I had to use a DOS emulator (DOSBox) to get it to work. I seem to recall that the ICE program itself had a considerable error in Delta-T, though. I presume that was rectified for the web version. Some years ago I mentioned that I had purchased MICA (probably because of the errors in ICE) and was slightly disappointed in some of the changes. You asked what it was that I liked about such an old, outdated program. I replied that it was mainly the change from the style of output that the USNO website still uses. It was much more user-friendly for celestial. MICA gives positions in SHA and you have to take the additional step of having it calculate GAST and LAST to get GHA and LHA respectively. MICA also did away with the second part of the output - the altitude corrections. Also, Hc and Zn are not included in the same calculation. You have to calculate them separately.
Speaking of MICA and Delta-T: a couple of years ago I mentioned that the error in MICA's predictions was growing. At the time it was just over half a second. Today it is over one second (+1.186184 seconds, to be exact). There is a page on the USNO website which lists updates to MICA's Delta-T file, but it has not been updated since the last edition of MICA (2.2.2) was published. The date of the first prediction being July 2nd, 2011. I wonder now, as I did then, when (if ever) the USNO will see fit to issue another update. Perhaps I will have to pick up where I left off learning how to code an ephemeris and develop my own version of ICE. I think there may be a book or two in that collection I bought from Ken that would help me accomplish that.
Attached is a graph of the growing error in MICA's Delta-T predictions and a zip file of the old ICE program. I have not found the source code for ICE online - and I don't know if it could be decompiled or modified to update its Delta-T values. But if there is someone out there reading this that knows if and how that can be done, I would love to have an updated version (DOS format and all - because I like DOS). I might even be willing to pay for it. ;)