Re: Ic Photometry

[Arne Henden <aah@nofs.navy.mil>]

Got me; that is a strange one.  What calendar date does 2820
correspond to?  Anything unusual, like bright moonlight or southern-only
clouds?
Arne

Thomas Droege wrote:
> Looking at the attached plot, a big dip will be noticed in the Ic
> photometry.  There is a much smaller dip in the V photometry.  This occurs
> on a number of the plots.  All so far that I have looked at are from TOM1.
> 
> The dip always happens around day 2820 but there are several days in a row
> where the dip is evident.
> 
> At this time, the weather was hazy to the South.  TOM2 which points mostly
> up did not have a problem.  TOM3 which points to the North also does not
> seem to have this effect.
> 
> The Question is:  Why the Ic dip?  
> 
> I have no doubt that the haze cut down the light received for stars near
> the horizon.  But why do the V measurements come out pretty good while the
> Ic measurements are a mag or so too faint.   Note that I have lots of
> measurements, so I can find long period variables that show this problem
> and which confirm that the V measurements are pretty good - they follow the
> trend of the long period variable.
> 
> Tom Droege
> 
> 
> 
> 
> 
> 
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