This attribute indicates whether or not cards should be removed from the
FitsChan if
an error occurs within
astRead. A succesful read on a FitsChan always results in the
removal of the cards which were involved in the description of the returned
Object.
However, in the event of an error during the read (for instance if the cards in the
FitsChan have illegal values, or if some required cards are missing) no cards will be
removed from the FitsChan if the Clean attribute is zero (the default). If Clean is
non-zero then any cards which were used in the aborted attempt to read an object will
be removed.
This provides a means of "
cleaning"
a FitsChan of WCS related cards which works even
in the event of the cards not forming a legal WCS description.