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MapPoint | ScopeDome Australia

ScopeDome Australia - MapPoint

It is not uncommon for the mount and pier to be off the geometric centre of the dome to achieve the best telescope viewing within a dome. It is also not uncommon for users to desire different pier heights for their own personal preference. In regard to different brands of mounts, the design of each mount, even of the same type be it German equatorial, fork or another type of mount, the position of the telescope relative to that mounts RA/DEC can vary dramatically its optical viewing path to that of the dome aperture/window. This is where Map Point comes to assist in ensuring the best dome position is achieved for your equipments configuration.

As this is the case, the standard analytical function that calculates the best position of the dome knowing the telescope position is often insufficient. It is also very sensitive to the measurement accuracy of the telescopes position relative to the geometric centre of the dome. The MapPoint procedure accurately helps to set the dome rotation for the relative position and inclination of the telescope.

In most cases, the standard analytical function will closely match the domes rotation to the optical viewing path of the telescope. But, because of the potential variations mentioned above, the overall positional calculations may need fine tuning. The MapPoint program allows for a list of manually pre-mapped points that help to synchronise the calculations of the dome position to the telescope position.

By mapping we mean here to save the mutual position of the telescope and the dome. While completing this mapping, the dome must be manually set in the best position so that the telescope optics are directed to the centre of the dome's window. There is no need to map the entire sphere. We map only those areas where the standard calculation poorly sets the axis of the telescope to the dome. The minimum number of mapped points at which MapPoint function starts to work is three (x3) points. MapPoint takes into account the position of the telescope relative to the pier (PierFlip - from version ScopeDome USB Driver). We can save the best position of the dome while the telescope is set on a given point in both the eastern and western side of the pier. This is important especially when the telescope passes through the meridian around azimuth 180⁰.

How to start mapping the points?

  1. In the "Config" window, "Telescope / Site Info" tab, please provide the exact coordinates of the observatory, and configure the connection with the telescope.
  2. In the "Config" window, "Dome" tab, please choose the parameters as accurately as possible, "Dome Geometry" to let the standard procedure work as accurately as possible. This will allow us to map the minimum number of points. Standard procedure usually fails only near the zenith and the meridian.
  3. In the "Config" window, "Program" tab, please select "Use Map Point" .
  4. Then close the "Config" window by pressing "Save Settings".
  5. Connect the dome with the telescope by pressing the "Conn" button in the "Telescope Command" group in the program main window.
  6. We can now open the "Map Point" - for this purpose press the button "Map Point" in the main window.

MapPoints function window

After initial configuration described above we can generate a grid of points on which MapPoint function will calculate the position of the dome in relation to the telescope position. We have two possibilities:

  1. Generate Flat Mesh - this option generates a flat grid of points for which the telescope position is equal to the position of the dome. Probably in this case there will be a need to map all the points of the grid.

  2. Generate Dome Mesh - this option generates a grid of points on the basis of the standard procedure for calculating the position of the dome in relation to the telescope. Thus we can map only the places where the standard procedure fails, and the remaining points we left unchanged.

To generate the grid points, respectively, press the button "Generate Flat Mesh" or "Generate Dome Mesh." We can also clean the mesh by pressing the "Clear Dome Mesh" and manually add all points to the grid.

Mapping the points

How to map points of the grid?

  1. Select a single point on the graph by clicking in it.
  2. Press the "Slew To" button in the "Scope Position" group - this will set the telescope to the coordinates of the corresponding point of the grid.
  3. Press the "Slew To" button in the "Dome Position" group – this will move the dome to the azimuth corresponding to the point of the grid.
  4. Correct manually (using the CW and CCW buttons from the main window) the position of the dome so the telescope optics was looking at the centre of the dome shutter.
  5. Press the "Map Point" button in the "Map Point" window.
  6. Repeat this procedure for all points where the dome is badly positioned in relation to the telescope.
  7. Manually mapped points are marked with a darker colour.

Manually adding points

If there is a need to later add an additional point, set the telescope to any position and set the appropriate position of the dome, and then press the "Add" button in the "Points" group. "Delete" button deletes the selected point chosen by the mouse. Before a full mapping of the dome we advise you to practice it at first on several points, and then clear the grid by pressing the "Clear Dome Mesh". The quickest way to map points is to move on the grid by the columns from bottom to top. In this way we will do the least amount of dome moves. Double-clicking on the grid moves the telescope to the coordinates indicated by the mouse. You can enlarge the grid by selecting the area by the mouse.

The parameters of the MapPoint function

In the "Test" group, there are two parameters that determine the functioning of MapPoint:

  1. "Accuracy" (degrees) - if the position of the telescope is located at a distance from the grid point less than the value of "Accuracy"- this point is selected.
  2. "Radius" (degrees) - the radius where the algorithm seeks the triangle points to calculate the position of the dome. If the points are not found, to determine the position of the dome it will use the standard algorithm. There is usually no need to change these parameters.

Saving mapped points

After completing the mapping procedure press the "Save" button to save the list of mapped points permanently in the configuration file. A question about saving a file with the points will also appear when you close the window "MapPoint".

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