From: mikkelhaaheim@gmail.com   
      
   Le vendredi 16 septembre 2016 12:10:12 UTC+2, Sea Wasp (Ryk E. Spoor) a   
   écrit :   
   > On 9/15/16 2:27 PM, Mikkel Haaheim wrote:   
   > > Le jeudi 15 septembre 2016 17:57:19 UTC+2, Mikkel Haaheim a écrit :   
   > >   
   > >   
   > >> Once detected, you need processing power to identify a source as a   
   "legitimate" target. You need to eliminate all background sources. To   
   understand how many sources have to be eliminated: someone had calculated that   
   a "torchship" (fusion powered    
   rocket) at full thrust would have a magnitude of +12 (he did not specify if   
   this were absolute magnitude, or apparent magnitude at 1 AU or so, so I will   
   assume apparent, which would actually yield a brighter absolute). This roughly   
   coincides with the    
   detection limit of a 5" to 10" telescope. Now, consider the hundreds to   
   thousands of stars visible to the naked eye on a clear, dark night (the milky   
   way)... and consider the tens to hundreds of thousands of stars and galaxies   
   that become visible with a    
   5" telescope. This is the background you have to elliminate before detecting   
   an unsheilded fusion drive.   
   > >   
   > >   
   > > Right. I actually have a little more precise information.   
   > > I found a source that reports 156 182 070 295 stars catalogued with   
   apparent magnitudes of 12 or brighter.   
   >    
   >    
   > 	And if you have them catalogued, a modern computer will be able to    
   > notice "hey, that sucker just appeared out of nowhere and isn't in the    
   > catalogue" in less time than a human can notice.   
      
   Not when you are talking about tracking billions of these sources. Not even   
   when you are talking about tracking millions. Those computers you mention are   
   still trying to extrapolate information from 50+ year old photographic plates,   
   trying to track all    
   those known sources in order to identify and catalogue the unknown ones.   
   Various computers and astronomers have been doing this for 30 years, and they   
   STILL have only been able to catatlogue a small fraction.   
      
   >    
   > 	This is a trivial job. You include the catalogue as part of your scan,    
   > and look for *change*, not analyzing everything from scratch.   
   >    
   >    
      
   No. It is NOT a trivial job, as evidenced by the fact that these sources   
   sontinue to make it difficult to identify the remaining sources that have   
   already been recorded for nearly 100 years.   
      
   >    
   >    
      
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