On the lamp in the dome we can test the densities of the various ND filters by calculating and comparing the observed fluxes with and without the filters. So far I have tested most of the ND0.9 filters. They appear to be blanks – or have not rotated into position.

Filter Without ND With ND0.9
B 3511 3512
V 26500 26500
VE1 210700 209700
VE2 268200 273000
IRCUT 196050 no data

The numbers are in counts/second and are based on the measured mean counts in the various frames and the exposure time MEASURED and reported in the FITS header.