[sac-forum] Re: Messier 2 Declination Error

AJ, my first thought is my Celestron NexStar goes right to M2 when asked to. But then thinking about this some more: if the -0 : 49 becomes +0 : 49, this is only a 1.63° difference and it wouldn't show up necessarily as an easily detectable error because the scope would still place M2 well in my ~ 1° TFOV. It would be interesting to do a "get ra/dec" following the slew to see if the zero value is plus or minus - if the skies ever cooperate again.
Or, am I missing something here? 
Bob





AJ Crayon wrote:
Has anyone had problems locating M2 with digital setting circles or a GoTo system? This involves any of the electronic systems. I have run across declination errors with this entry on the XP4 Flash Sky Commander digital setting circles and on Orions SynScan GoTo system. Reason is because the declination is -0° 49' and the way computer hardware handles -0. Turns out most computers convert -0 to +0 resulting in incorrect calculations. I corrected my version of XP4 with an update the the Messier catalog when this was discovered some time ago. I have just found the problem in the SynScan system and notified Orion this morning. So, I ask, has anyone else had problems with their system finding M2? 

AJ Crayon
Phoenix, AZ

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