Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!uhccux!galileo!ressler From: ressler@galileo.ifa.hawaii.edu (Mike "IR" Ressler) Newsgroups: sci.electronics Subject: Re: Sidereal Time Clock Message-ID: <10633@uhccux.uhcc.Hawaii.Edu> Date: 13 Dec 90 02:33:43 GMT References: <1833@umriscc.isc.umr.edu> <1990Dec12.214854.19076@swbatl.sbc.com> Sender: news@uhccux.uhcc.Hawaii.Edu Distribution: sci.electronics Organization: UH IfA and NASA Infrared Telescope Facility Lines: 21 In article <1990Dec12.214854.19076@swbatl.sbc.com> ken@swbatl.sbc.com (Ken Gianino 5-9081) writes: >In article <1833@umriscc.isc.umr.edu> robf@mcs213j.cs.umr.edu (Rob Fugina) writes: >>My roommate just asked me to design a clock for him. It's for astronomical >>purposes. Relatively simple, really, but I need a little advice and some >>chip numbers. >> >>The clock has to count from 00:00:00 to 23:56:03, then reset back to zero. > > Why 23:56:03? Doesn't sidereal time use 24 hours and just lose 4 min/day? I'm glad someone caught this. Sidereal time is indeed at 24 thing, it's just that the hours are slightly shorter - 1.002737909 times shorter (23h 56m 4.09053s to the sidereal day). You just need to design a normal 24 hour clock that uses a clock frequency shifted up by this amount. Very vague recollections say that someone actually made 1.002738 MHz crystals, but I have no idea who. Good luck. -- Mike Ressler - Infrared Photon Jockey ressler@galileo.ifa.hawaii.edu If at first you don't succeed, get a bigger sledgehammer.