Re: experiments

[Michael Gutzwiller <deepsky@fuse.net>]

To all,

Even as I write this I am experimenting with making an independent flat
field. 

What I did was drape a thin tablecloth in front of the triplet earlier
tonight.  It was illuminated only by the ambient light of late
twilight.  I ran the triplet as normally for the full exposure time. 
This was adequate for the purpose it seems.  The tablecloth seemed to
transmit much better through the I filters than the V filter though. 
The V values were only 1000 ADUs above the dark field but that's
probably enough.  As with the sky flats I have been using the peak to
trough range was of the order 5 to 8 percent.

I am now taking normal data and will compare the sky flats to the
tablecloth flats.  I will compare them directly by dividing one by the
other and I will also compare the magnitudes computed with each in the
normal images.


Mike G.