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
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
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
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
Passive, do the placing of the guide star in the box manually.
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.
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
brightest guide star is moved to the center of the star box wherever it is
and autoguiding started.
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
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
For staff interested in on-line details about the auto positioning, status page 27 contains most of it.