74" / 1.9m - Instrument Selector

Instrument Description

The "Instrument Selector" is essentially a new fold mirror that has been installed in the acquisition boxes of both SpUpNIC and HiPPO that allows the observer to switch between two instruments: a "primary" and a "secondary" instrument where the primary instrument is either SpUpNIC or HiPPo and the secondary instrument is a new SHOC system. In other words, SHOC is from now on permanently available on the 74-inch.

Below is the image showing the new SHOC system mounted to the side of SpUpNIC's acquisition box. The new SHOC system replaces the old guider box that use to migrate between SpUpNIC and HiPPo with a newly designed off-axis "pick-off" guider system that can accommodate a filter wheel unit and SHOC camera behind the guider.

To select between the primary instrument and SHOC, a user can actuate the fold mirror in/out to steer the science beam towards the desired instrument (see figure below for button on TCS that actuates the fold mirror). When the fold mirror is IN beam and the guider's XY stages are "centred" then the guider camera is functions as a "target acquisition" camera for SpUpNIC/HiPPo, similar to the old system. Also, as in the old system the guider can patrol the area of the large annulas mirror to acquire an appropriate guide star.

NB. Because the fold mirror and annulas guide mirror are displaced relative to one another in the optical z-axis the guide/acquisition camera's focus has to be adjusted substantially when switching between guiding and target-acquiring mode. This cheat-sheet provides guidelines for focus settings and summarises instructions how to set up target-acquisition and guiding for the primary and secondary instrument: