Re: Ic Photometry

["Thomas Droege" <tdroege2@earthlink.net>]

Arne and all,

Yes, as noted below in the message, there was a haze to the south.  The
question is how does that make it through the pipeline as a decrease in
brightness of most of the Ic measurements?  Michael could you comment? 
Does a haze cause more loss in Ic than in V?  Even so, should not the
photometry step take care of this?  The Ic measurements are being compared
to all the other Ic measurements??  So I should be able to put a neutral
density filter in front of the Ic telescope and not change the photometry??


Puzzled.

Tom Droege


> [Original Message]
> From: Arne Henden <aah@nofs.navy.mil>
> To: <tdroege2@earthlink.net>
> Cc: tass <tass@listserv.wwa.com>
> Date: 10/6/2003 1:02:45 PM
> Subject: Re: Ic Photometry
>
> 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
> > 
> > 
> > 
> > 
> > 
> > 
> > ------------------------------------------------------------------------
> > 
>