Imaging

To determine the alignment of the detector with the focal plane of the telescope we have made various through focus tests doing a series of exposures stepping the telescope focus in between. We have seen variations of the best focus from the center to the edge, and from one side to the other indicating some misalignment, but tests at different telescope and rotator positions have given rather different results. We plan to investigate this further to understand what is causing this.

Two narrow-band and one intermediate-band blue filter were provided by G. Östlin and their characteristics were added to our data base.