REM SCript to create todays folders and start client apps 
csript 
start /nowait c:\program files\maxim\maxim_dl.exe
start /nowait c:\program files\skymap\skymap.exe
start /nowait c:\program files\guidedog\guidedog.exe
cscript c:\documents and settings\administrator\desktop\astronomy\createTodaysFolder.vbs

Following discussions on the web regarding flatfielding mechanisms ranging from twilight sky exposures to stretched white 
shirts to moreelaborate light boxes I decided I needed to do something - my exposures were inproving on guiding and thus duration 
and the dust doughnuts more prominent on the fainter items of low surface brightness. also the vignetting of field is easily apparent.
So I began collecting the polythene corrugated sheetsused in supermarkets to separate trays of milk in the fridges.
These are 20" by 12" or so. I collected about 8 of these for nothing while shopping
I also happened across some rigid ploythne foam packing of 8" internal diameter, 
10" external used for packing on something, 
Putting this all together I applied a lot of hotglue gun glue to knock up a flatfield box that fits snugly on teh end of the telescope.

The steps were: 
cut a 12" square from teh available corrugate sheet
Cut an 8" hole in the 12" square and glue it to the foam ring using the hot melt glue
Cut 4 remaining pieces 12" on a side. At this point I scored one edge 1" or so in and all the way along for folding. 
I then rotated it 90 degrees and scored it again, cutting out  the corner area where the scores overlap. 
Rotate one last time and score again. 
Finally lue one of the scored flaps down to the ring base flat board surface, flap face into the centre.
Glue the adjacent side to it, using the base flao to attch to the base board and the side flap to glue to the adjacent side.
Finish all four sides. 

This leaves the top.
The top I actually bought a nice coated foam cell sheet from Hobbies hobby materials store - its 3mm thick 
foam card and quite consistently matt white in colour and quite opaque. This was cut to a square and glues to the end flaps. 

The light source was added - these are a set of 10 pea bulbs, again from Hobbies which attach to a battery holder. The bulbs were hot glued by their leads
to the the edge of the the ring and the battery holder threaded outside of the entire affair and glued to the base of the ring. It has a built-in switch, 
so there is no wiring to do. 

At last to the test. There is a picture which gives nothing away quantitatively but looks quite flat by eye.

To consider the quantitative flatness of the resulting field imaged into the telescope I created a numerical model 
Consider: 
The illumination on an object follows an inverse square rule with the distance from the light source
FOr each light in the set of pea bulbs I calculate the distance at a matrix of points on the flat plate. 
If the pea bulbs are each at position X,y,z then the distance to each point on the flat plate is sqrt((X-x)^2, Y-y)^2 + (Z-z)^2 ).
KNowing the distance I can calculate the relative illumination on each point assuming each bulb is teh same brigtness by adding up the contribution on each point from each bulb.
The final part of the equation is to vary the distance between the flat plate anf the bulbs in the model and compare the relative flatnesses 
of the resulting curves to determine the best distance between the ned of the scope and the flat flate for field flatness purposes. 
The results are below. 

The result needs to be normalised for the variation in brightness due to the varying distance by multiplying by the square of the distance modelled for.