HATS Pointing Model

The Sky X pointing model interface

Introduction

The Pointing Model is a function that corrects the telescope pointing. The function is composed of several terms each one has two factors: a function of the telescope coordinates that can be a trigonometric or polynomial; and a parameter that multiplies the function. The final correction value is obtained by adding all the different terms. $\Delta x_i = \sum f_i(x_1,X_2) \times A_i$ where $_1,x_2$ are the telescope coordinates (they can be azimuth and elevation, or right ascension and declination), $f_i$ are the different functions, and $A_i$ are the parameters. Examples of functions are $\Delta h = -MA \cos h \tan \delta \quad \Delta \delta = +MA \sin h $

HATS uses TPoint to obtain a pointing model from measurements done during observations. At present, HATS pointing model has 7 functions. The following table shows the parameter names and their values as of 2025-04-13:

  Name     Value
  ID       -815
  ME      -9106
  MA      +8852
  HHSH     -922
  HHCH    -2577
  HDSH    -7163
  HDCH    +8714

This model was developed by Patrick Wallace, the developer and owner of TPoint software. It is important to note that when we talk about a "model" we may refer to two different things.

1. The set of functions to use. HATS model uses 7 functions described in the TPoint manual.
2. The value of each parameter

Measurements

(Needs to be written)

Model determination