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    Re: Preparing the sky with Vol. 2 and 3 Pub. 249.
    From: David Pike
    Date: 2017 Sep 24, 13:51 -0700


    How can I best prepare the sky with other stars then the selected stars in Vol. 1 (Pub. 249) [marked with a "diamond"] to get a good intersection of position lines ?

    Regards, Guus Dekker, Belgium.


    It is possible to use Vols 2 & 3 of HO249 for star shots as well as for Sun and planet shots, but only for stars with declinations between 30S and 30N.  Such stars can be found by going to Vol 2 or 3 and going to page (iii).  There you will find a list of the 57 navigational stars in both alphabetical and SHA order.  Those marked with an asterisk are not in Vol 1 but have declinations between 30S and 30N.  I suspect the stars in full capitals are the ones that do appear at least once in Vol 1.

    You could get a rough idea of cuts by comparing SHAs.  Alternatively, you could download the Air Almanac from here http://aa.usno.navy.mil/publications/docs/aira.php and look at the Sky Diagrams starting at page A24.  Then again you could purchase a Planisphere like the Phillip’s.  Finally many commercial celestial reduction apps include bespoke sky diagrams.  You simply put in your lat and long and press either ‘Now’ or a time of your choice, but if you’re using such an app, you probably no longer need HO249.  Good observing. DaveP

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