4/8 Point Test

This test measures the basic azimuth and elevation offsets of the structure. The basic idea is to run tracks that are horizontal or vertical where the majority of the correction will be in azimuth or elevation. These corrections are then applied to the structure and the test may be run again to refine the corrections.

4 Point Test

Run trajectories at the cardinal points. Select objects (e.g., stars from F9 catalog, set up on the IHMP center position IFU=000) that are close to the center of the track (within 3 minutes) for best results. The cardinal points are

Azimuth	Dec
0.000	65.626	north trajectory
65.452	38.530	east trajectory
180.000	-4.263	south trajectory
294.458	38.478	west trajectory

Store images on the ACQ camera and all probes during the test. Assure good focus, un-saturated target star, etc. On each target, record the actual true azimuth of the structure, the parallactic angle, and the X,Y offsets required to get the object to the correct position on the ACQ camera.

The north and south trajectories should require close to the same offset as should the east and west trajectories. The north/south Ra correction should be similar to the east/west Dec correction and it should be applied to the azimuth correction, while the north/south Dec should be similar to the east/west Ra and is applied to the elevation correction.

The correction should be applied with reversed sign to the AOFF and EOFF values in the source file <trunk>/legacy/etc/structureModel.dat. This file should then be installed and the legacyServer restarted to pick up the change. The values may be changed temporarily in the file /opt/het/hetdex/etc/conf/structureModel.dat, however, you will need to use sudo to override the read only file permission.

8 Point Test

Basically the same as the 4 Point test but with more points. Do a test also at the intermediate points as given in the table below.

Azimuth	Dec
24.059	60.236
125.414	7.632
234.586	7.632
335.941	60.236