Re: Bits and pieces

[Chris Albertson <chrisalbertson90278@yahoo.com>]

One more option:

You could save the processed image with corrected
header and darked/flattened pixels AND then write the raw
pixels as a second image extent in the FITS file.  OK that
doubles the file size but a simple gzip compress would result
in a file only 30% larger then an uncompressed raw pixel file.

FITS viewers will ignore the second image and display only the
first one by default so the raw pixels would still be there
if needed.

That's a long way to say "you could save both".



--- Stupendous Man <richmond@a188-l009.rit.edu> wrote:
> 
>   I wrote:
> 
> >  One can recreate the master dark
> >  and flat from the raw images, but that will take several minutes.
> 
>   Tom asked:
> 
> > How do you get a master dark from the object images?  I have
> assumed that 
> > you can only get flats from the object images???  Also you can't
> get a 
> > light box flat from the data, and at least I have been convinced
> that there 
> > are problems with a sky flat due to the gradient in the sky.  
> 
>   Sorry about that.  What I meant to say was:
> 
>      One can recreate the master dark
>      and flat from ___a complete set of raw images, including darks
>      and lightbox flats___.
> 
>   So if the darks and lightbox flats are not kept in the same place
> as the raw sky images, it takes more time and effort to put them
> all together for re-reduction.
> 
>   Tom is correct when he warns
> 
> > [there] are problems with a sky flat due to the gradient in the
> sky.
> 
> I agree that using sky flats is not a good idea.
> 
>                                              Michael
> 
> 


=====
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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