Problem(s) Encountered:

We met a problem at the last exposure of the observing. The guider doesn't work. We try to restart the guider's software; but it still doesn't work. Last night the guider camera works. But when we selected the guide star (bight enough), it cannot have a good fit for the guide star. It shows 'star fade' or something like that

Solution:

'Star faded' usually means that the software cannot locate the star, usually due tosome error in using the functions within the Gude tab.  If the star first lands at somerandom position, you have to 'Expose' first within the Guide tab to locate it.The 'Expose' button also enters the X,Y position of the Guide star that you can see in the second row.  It also sets up a virtual 64x64 box around the X,Y position that it will use to look for any future Guide star.  Then you are ready to 'Track'.
 
If a future guide star does not land within the same box, you have to 'Expose' firstto find it and reset the X,Y position.  Otherwise, it thinks that there is no star, orthat it must be cloudy.

 Also, if the star is too close to the edge of the image so the 64x64 box is notcontained within the image, it might not find it.