Re: Data reduction methodology for V-I colors

[Thomas Droege <tdroege2@earthlink.net>]

There has been a lot of work done to try to determine what can be done to
improve the qulaity of the tass data.  I think it would be useful for those
interested in trying to make an improvement to read
TN88,89,90,92,94,95,97,98, and 100.  A lot of things have been studied.

If you think you have a new and better idea, then as always I can send a
data set.  One more reason to get the raw images up on a data base
somewhere, then you all could pick out data sets to process.  As it stands
now, to get a useful data set I have to sort through thousands of CDs. 
This is something I plan to do this winter when there is ice on the roof
and I don't dare open the dome in the unlikely event the night is clear.  

Tom Droege


> [Original Message]
> From: Chris Albertson <chrisalbertson90278@yahoo.com>
> To: <tdroege2@earthlink.net>; <tass@listserv.wwa.com>
> Date: 8/31/2004 1:53:52 PM
> Subject: Re: Data reduction methodology for V-I colors
>
>
> Could it be that the zero point is really a function of
> (x,y) on the frame and that using one "zero point" for the
> entire frame is only a gross approximation of the true
> "zero function".  It seems unlikely to me that the atmosphere
> really is equally transparent over a degrees wide field.
>
> Professionals may  have been using zero points for years but
> how many of them use wide feild images?
>
> One experiment might be to plot the difference between
> instrumental and catalogged magnitutes and see if the differences
> "clump" togeter.  If there were a cloud blocking
> half the frame you would see it.  But more subtle effects
> might also be detectable.
>
> If the transpaarency does vary across a frame at the few percent
> level then maybe you will have to compute some kind of "zero
> function".
>
> The "gradient" Tom talked about seems like it might headed in 
> this direction.  "gradient" is a kind of fuction (a first order
> one.) but I supect a tilted plain will not fit much better then
> our current zeroth order function.  The physical atmosphere is
> likey bumpy with sharp discontinuities.
>
>
>
>
> --- Thomas Droege <tdroege2@earthlink.net> wrote:
>
> > I will leave this for Michael.  I have just looked at data sets as a
> > whole.
> > Why not join in the fun?  There is lots of data.  Andrew, Michael and
> > I
> > have been working on this.   There is room for more clever minds to
> > puzzle
> > over the data.  As always, I stand willing to copy CDs for anyone
> > willing
> > to compute on the data.  
> > 
> > Tom Droege
> > 
> > 
> > > [Original Message]
> > > From: Michael Koppelman <lolife@bitstream.net>
> > > To: <tdroege2@earthlink.net>
> > > Cc: tass <tass@listserv.wwa.com>
> > > Date: 8/31/2004 12:24:00 PM
> > > Subject: Re: Data reduction methodology for V-I colors
> > >
> > > But aren't you getting a different zeropoint solution for every
> > frame? 
> > > Why not use a single zeropoint for the entire night?
> > >
> > > On Aug 31, 2004, at 12:20 PM, Thomas Droege wrote:
> > >
> > 
> > 
> > 
> > 
>
>
> =====
> Chris Albertson
>   Home:   310-376-1029  chrisalbertson90278@yahoo.com
>   Cell:   310-990-7550
>   Office: 310-336-5189  Christopher.J.Albertson@aero.org
>   KG6OMK
>
>
> 		
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