In the ~5 years that GOTO has been operating, the primary mirrors have picked up a lot of dust, debris, and volcanic ash which scatter light and reduce the performance of the telescopes. Slowly, we’ve been seeing a decrease in our limiting magnitude and an initial test, cleaning one telescope, showed that most of this could be attributed to the dusty mirrors and correcting lenses.

This led to the decision to fully clean the GOTO-North mirrors, for the first time since the system was installed. With 16 telescopes per site and two mirrors per telescope there’s a lot of work to be done!

Cleaning GOTO’s Primary Mirrors

As in most telescopes, the primary mirrors of GOTO are first surface mirrors, which means that the reflective coating is applied on the front of the glass substrate rather than behind it. This is great for optical quality, but also makes the surface a lot more delicate so some care has to be taken when cleaning the mirrors.

Last month, we went out to disassemble, clean, and assess the condition of all sixteen telescopes that make up GOTO-North, which also meant reassembling the telescopes and getting the array back into working order before we left.