Auto positioning on the NEW TCS

The auto positioning is intended to save time when presetting to an object and also to give better centered objects. If in use, after the preset has finished and TV filter has been automatically set to Open or Grey, the autoguider program moves the star box to a suitable position around the weakened central area of the guide camera. It also puts the background box at lower left which should give a better margin for the guiding. The star box positions are choosen from a 100 slot circle around the center, with a radius of 5.5 arcsec. The same position is used for an observing run. The guide probe is counter moved for the additional box adjustment from the center to give the same pointing as if the box was in center. If this method conflicts with other setup intentions then switch off autopositioning. When the initial adjustments are made the autoguider program will try to identify between 1 and 3 candidates as guide stars. In the full mode only one (the brightest) is looked for and if found the telescope is given a horizontal offset in order to move the guide star to the center of the star box, wherever the star box is placed, then autoguiding is switched on. In the semi mode up to 3 stars will be looked for, they will be marked on the autoguider screen. The observer can then choose one of them by giving 1, 2 or 3 on the user interface terminal as a command, the corresponding guide star will then be moved (with a telescope horizontal offset) to the center of the star box and autoguiding will be started. If instead a 0 is given the auto positioning is skipped. If You are too fast to choose 1 before the other 2 have been found then an error message is given saying that no one is available, then just give the 1 again after the 3'rd has been marked on the autoguider screen.
The choosen mode is displayed on the user interface terminal at the upper part under the CCD filter info.
The available commands (can be shortened) are

Auto-Positioning-Off

Passive, do the placing of the guide star in the box manually.

Auto-Positioning-Semi

Up to 3 stars are searched for and marked on the autoguider screen, choose one of them with 1, 2 or 3, or 0 to skip it.

Auto-Positioning-Full

When command is given the star box is moved to the center of the autoguider screen. At presets the box is moved to a position close to the center of the screen, the brightest guide star is moved to the center of the star box wherever it is and autoguiding started.

Auto-Positioning-Retry

The autoguider program will try again to search for guide stars according to the choosen mode. Can be useful in bad seeing if TV filter Grey was choosen, no star was found and another brighter filter was set by the observer.


The mode is automatically set to OFF at noon to avoid having it in operation during sky flats, that could cause confusion.
The FULL mode seems to work in most conditions but sometimes it might be better to use the semi mode in difficult cases (bright sky, bad seeing, clouds).

All the described commands are also available from the instrument sequencer even if only the Auto-Positioning-Off and Auto-Positioning-Full could be useful.

For staff interested in on-line details about the auto positioning, status page 27 contains most of it.
(updated 2013-09-26)