First DECam Guiding

In a previous blog post (The DECam guider), I wrote about the first stages of testing the new DECam guide system.  Progress was made quickly at first, but then slowed down.  Eventually, the guide system expert, Santiago from Spain, hopped on an airplane, and 50 hours later (nightmare travel), he arrived on Tololo.  But Santiago didn't sleep when he arrived on Tololo--he went right to work with the rest of the commissioning team.  Here are two of the more obscure issues that were encountered, and luckily, eventually fixed.

PROBLEM:  In "self" mode (when the guider automatically is supposed to select the guide star), no stars were identified.

SOLUTION:  It was discovered that there was a desynchronization between the guider readout and the CCD shutter.  A guider exposure of 300 ms was taken, but the CCD shutter would open only after this time was done.  With the CCD integrating during the guider readout, it is no surprise that no guide stars showed up!  The guide exposure time was increased to 1000 ms, and now, finally guide stars were seen.

PROBLEM: Although guide stars are selected, the guider was still not working.

SOLUTION:  The TCSINTERFACE command relays information to the telescope control system (TCS).  This value needs to be a float value, with no special characters.  Unfortunately, a RA=%5.2f in the code was adding a space!  This was a quick fix -- but only once identified.

This image shows the interface of the DECam guider--here one region of interest of one (of the four) guide CCDs is shown.  The "best" guide star is marked in green, and second guide star is also in the region of interest, to further help with accurate guiding. 

The guider is not working 100% yet, but it is exciting that the first guided images with DECam have been achieved.