Re: Magnitude range of images

[Stupendous Man <richmond@a188-l009.rit.edu>]

  Dirk asks:

> Those of you who have reduced Tom's images, what do you estimate the
> useful range of magnitudes is in the V frames?  ...
> .... By "useful" I mean the range over which we can hope to
> measure the brightness of a variable to +/-5% at the faint end.

  Look at Tech Notes 75, 76, and 77

     http://a188-l009.rit.edu/tass/technotes/tn0075.html
     http://a188-l009.rit.edu/tass/technotes/tn0076.html
     http://a188-l009.rit.edu/tass/technotes/tn0077.html

where you can find three independent analyses of Mark IV data.

  An executive summary might be that for exposures of 50 second
in Batavia, photometry reaches the +/- 5% point around V = 12.5, 
and saturation occurs around V = 8.0, I = 7.5.  But Andrew Bennett
and Jure Skvarc (and others, of course) should chime in if I've
misrepresented their results.  

                                               Michael Richmond