Re: TASS sees 500K unique objects

[Chris Albertson <chris@topdog.pas1.logicon.com>]

Gutzwiller, Michael wrote:
> 
> Arne A. Henden wrote:
> 
>     I would expect that 1/2 of the objects in the raw star lists should
>   be garbage.  
> 
> 1/2 seems awfully high to me.  Most of us are using a 3 sigma detection
> cutoff
> which shouldn't generate that many erroneous objects.
> 
> Mike G.

Correct, the match rate is much higher than Arne predicts.  Off hand
I'd say 1/8 are non-matches and that is with some of the data comming
from Glenn who uses a 2 sigma cut off.

If we were more interrested in discovery then 1% photometry then I'd
say we could set the cut off at ~1.5 sigma

I think seeding the catalog pays off.  A lot of the "junk" turns out
to be stars so dim they are seen in only one out of many "looks".

If I remember the numbers, 7.5M observations, 900K were single detections.
Of the 900K 125K were matches to the tassm16 list.  This means only
around 800K of the 7.5M are "junk".  In the months ahead more of this
junk may find a match.  I only had two month sample of data from three
sites.

Also not all the 900K are real junk.  Some areas had spotty coverage.
Remember if you run a tripplet (with 15 deg spread) even on a perfect
night one hour of data will be unmatched at each end of the run.
Another argument for co-alignment?

-- 
--Chris Albertson

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