Background

Accurate moves on the DEIMOS guider require that the DCS keyword TVANGL is set to the correct value. Although KSD 40 specifies that the value of TVANGL should be either 0 or 180, precedent exists for adjusting this value in order to set the guider angle correctly. This document describes how to measure and adjust the angle.

Requirements

Procedure

  1. Acquire star field. Point DEIMOS to a region with a moderate density of stars visible on the guider. A total of 10 stars or more is ideal for determining the solution.
  2. Save guider image. On the MAGIQ GUI, right-click on the image area and select Save as FITS to save the current guider image to the nightly directory.
  3. Analyze guider image. Load and analyze the image using the SKYMAP GUI as follows:
  4. Update guider parameters.
  5. Repeat as needed. Acquire a new image and check the angle as described above to obtain a new value of angle, which should be close to zero. Repeat above steps until values converge to zero.

Note

Figures

Skymap GUI

User Interface for the SKYMAP tool