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    Re: Pub.249 Epoch 2020 is available.
    From: Frank Reed
    Date: 2018 Nov 3, 11:00 -0700


    You're now describing an entirely different system which would require substantial tables distinct from those present in simple lookup tables like Pub.249.v1. You are not simply updating Pub.249.v1 at this point. The system you're describing would appear to require a lot more work from the navigator. It seems that you're suggesting that you expect the navigator to acquire the changes in SHA and Dec from some other source, like the standard Nautical Almanac, and then run those changes through some other tabular process, and then apply the changes to the initial Hc and Zn values. That completely cancels out the whole point of using Pub.249.v1. Yes, it would work. So would a thousand other crazy complicated systems. On the other hand, if you're saying that you're also going to tabulate the changes in SHA and Dec for each star, too, well not only is that another substantial addition to the tabulation, it also would either have to ignore aberration (which means one minute of arc accuracy at best --not a bad thing necessarily) or you would need still another set of tables to handle that. 

    Frank Reed

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