We were awarded five nights in December to test ANI, beginning December 9. Unfortunately the skies were rarely clear, the winds were cold and stiff. We spent much of the time brainstorming ways to determine whether the interferometer was aligned well. For the light from the two telescopes to interfere and cancel out the difference in the length of the path the light takes through each telescope needs to be different by a VERY small amount. Our estimate was that we needed to place our mirrors within an accuracy of 0.1 mm (about the width of a strand of hair) to be able to see interference. Since my instrument was built, rather crudely, in a matter of months I was not able to build it to this precision. This forced us to search for the point of equal path length by adjusting the path length one beam took at a very slow rate and monitoring our image to see whether we saw any cancellation of starlight. The diagram below is a schematic of our instrument.

The left beam is reflected by a fold mirror and transmitted by the 50% transmissive beamsplitter before coming to focus at the 10 micron infrared detector. The right beam is folded down through two fold mirrors to reflect off the underside of the beamsplitter coincident with the right beam. In this way the light from the two telescopes is interfered. We adjusted path length by moving the beamsplitter up and down to change the relative length the light travels through each telescope.

Although we had one clear night the last night, we were unable to adjust the interferometer so that the light from the two telescopes interfered. I returned very discouraged and uncertain we had more time to test the instrument. Luckily, we were awarded four more nights in January since the MMT's renovation schedule had been delayed.