Sky Charts 

Encoder telescope plugin

This plugin can be used with encoder box using the Tangent protocol like the Ouranos , AAM or NGC-MAX box.
It use a floating two stars alignment method based on the article by Toshimi Taki in February 1989 S&T.

Please refer to the manufacturer information to connect the telescope to the computer and power on the telescope.
Then use the main menu Telescope to select the encoder plugin and start the interface. If you are asked to change the program time to auto-refresh reply Yes. The following window is displayed :


For the first time use you need to provide some configuration information.

Click the "Connect button", the light must change to green and the encoder count are displayed at the top of the screen.

Perform the following alignment procedure :

  • If you select 90 degree initialization :
    • point the telescope vertically for an altaz mount or parallel to the polar axis for an equatorial mount. It is important to understand that you must not point to the real zenith or pole but to the direction of your mount axis. Use of a fixed graduated circle or a stop piece can be of great help, see also the discussion about the Z3 parameter below.
    • Click the "Init 90°" button.
  • If you select 0 degree initialization :
    • point the telescope horizontally for an altaz mount or perpendicular to the polar axis for an equatorial mount. The above note also apply in this case.
    • Click the "Init 0°" button.
  • Point the telescope to a star, use a reticle eyepiece and enough power to precisely center the star.
  • Click the star on the chart.
  • Select "Sync current object" from the "Telescope" menu or the right mouse button menu.
  • Repeat the procedure for a second star. Beware to choice a star with enough difference along the two axis from the first star.

The position of the telescope is now displayed using equatorial and azimuthal coordinates.

You can now close the interface window by clicking the "Hide" button.
Refere to the main menu Telescope help to learn how to show the telescope position on the chart.

Remember you can refine the local precision by using "Sync current object" on a nearby star at any time, you are not limited with the number of initialization stars.
The couple of star used for the part of the sky the telescope is actually pointed is marked by a '*'.

The Clear button delete all the stars in the initialization list and return the interface in unitialized mode.
A mouse right click in the list allow to delete only one star from the list.

If your interface return status information this is indicated just below the coordinates.

You can also do the initialization without the chart by using a star list even this is probably less convenient. If you really like that check the "Use" box and select the star from the list, when this star is centered in the telescope click the Align button.

Main cause of error

Sometime the position show on the chart is not the one you observe in the telescope, there is many cause of possible error here is a short list :

  • Configuration error :
    • Encoder steps number incorrectly set, principally if you gear the encoder. Use a full mount rotation with a fixed remote reference to count the exact number.
    • Mount fabrication error not set.
    • Missmatch between azimuthal and equatorial mount.
  • The precision for a two stars alignment is dependent of a precise first direction initialization, use the Z3 parameter to correct a systematic error. There is however no need for a precise polar alignment or mount leveling.
  • Unadapted reference stars, the first two alignment stars must have enough difference along the two axis and be far enough in the sky.
  • Also avoid to select an alignement star in the direction of the polar axis, Polaris is good for an azimuthal mount but not for an equatorial.
  • Missing encoder count in the interface box, this may occure if you move the mount too rapidly or if the battery are low.
  • Misidentification of a reference star.


Interface configuration


Select the encoder type you use, if your model is not listed consult your documentation to find a compatible model, if you find none select the generic Tangent model.
Set the encoder count for a full rotation for both axis.
The read interval is the amount of time that elapse between two position query to the interface box. Use a smaller value for a smoother cursor movement if your box accept that and if your computer as enough power. Use a larger value to use less computer ressource or if your interface box as a limited output rate.
Check the mount type (equatorial or Alt-Az) you use and if you prefere to do the first initialization vertically or horizontally.

The mount fabrication error angle Z1, Z2, Z3 in degree are the one defined in Taki article :
Z1 is the amount by which the elevation axis is offset from the perpendicular to the horizontal axis.
Z2 is the pointing error of the telescope optical axis in the same plane.
Z3 can be considered a correction to the zero setting of the elevation circle.

Mesuring Z1 and Z2 can be a difficult task, but Z3 can be of great interest to help to initialize the mount.
As an example imagine your Dobson mount as a security stop 5 degrees above the horizon to avoid to flip the primary mirror. You can set Z3=5 and check the initialization at 0 degree. To initialize the mount simply put the telescope pipe horizontally to the security stop and click the "Init 0°" button, that's all.
You can imagine the same if the stop is 15 degrees after the zenith but in this case use the "Init 90°" button.

You don't need to set the observatory coordinates as this is automatically done from the location defined in Cartes du Ciel.

In the case of problem with the interface you can trace the protocol to a file by checking "Record protocol to a trace file".

The last check box let you choice if you want this window always visible at the top of the other.

Communication port configuration


Select the serial port (COM1 to COM8) where the telescope is connected.
Set other options (speed, data, parity and stop) according to the manufacturer informations.
Change the timeout values only if you encounter communication problem and after identifying the problem with the trace file. Do not set the timeout to a value greater than the refresh rate in the preceding screen.

Click the Save Setting button to keep your configuration for the next run.
Also save the default options in Cartes du Ciel menu to keep your interface choice.


Intelliscope support

Orion Intelliscope support was added by Gary Carpenter
 
Intelliscope  proceedure is :

  1. Set up Port Configuration
    9600,8,N,1
      Timeout 1000 mS
      Interval Timeout 1000mS
  2. Set up encoder configuration
      Type Intelliscope
      Steps for Alpha          9216
      Steps for Delta           9216
      Read Interval              1000 ( other values may work too )
      Mount Type                Alt-Az
      Encoder Init  Angle        90
  3. Turn on Intelliscope, and press enter atleast once.
      ( Note 1 : you can go through the alignment proceedure for the Intelliscope or not, the Cdc alignment is independent of the Intelliscope)
      Note 2: You must press a key on the Intelliscope once in every 15 mins or it will goto sleep, and you will have to reallign! )
  4. Press connect  and follow the nomal Cdc vertical and two star alignment.