\parindent 0pt
\parskip 0.3cm
%\section {Trouble Shooting}
\section {TROUBLE SHOOTING}
 
\subsection{Checking the Light Beam}

If the telescope is operating normally but you
can't see any images on the Finder TV, The Cassegrain TV or the 
CCD (at Prime), check the following possible causes:

\begin{itemize}
\item Is it cloudy? Go outside and look for yourself.
\item Is the dome closed or is the lower shutter vignetting the beam?
\item Is the dome open but pointing in the wrong direction.   This can
      happen if the dome is switched to MANUAL or if there is a malfunction
      of the dome rotation or the dome rotation encoder.
\item Are the primary or secondary mirrors still closed?
\item Is the finder cover closed?
\item On the Cassegrain A\&G box check that the autoguider probe
      isn't close to the centre and thus vignetting the beam.
\item Is the telescope somewhere near its nominal focus?  It sometimes
      happens that on startup the focus runs away to 62 {\tt mm}.
      At this setting the image is so far out of focus that it is 
      very difficult to see stars on the TV.
\item Are the TV cameras running normally with the gain fully up
      and no warning lights showing?
\end{itemize}


\subsection {The telescope is tracking but pointing badly} \label{ch13:etest}
\begin{itemize} 
\item Have you zeroset correctly and done a SNAFU? 

\item Check the coordinates (including proper motions) and the equinox. 
If you are observing a star with a high proper motion (several of the 
white dwarf spectrophotometric standards fall into this category), it 
is vital to include the proper motions and to beware of old finding 
charts.   Has the proper motion in Right Ascension A been entered in 
\secs/year (which is wrong)
rather than seconds-of-time/year (which is correct)? 

\item Has the telescope control software been initialised with the correct 
focus file? 

\item Are the encoders working correctly? Do a systematic check as follows: 
\begin{enumerate} 
\parskip 0.3cm
\item Stop the telescope and switch to Engineering mode 
\item Check the position roughly on the synchros. Is there a big pointing error:
      more than 2$^{m}$ in RA or 30\mins\, in Dec?  If so, shut down the
      Telescope Control System and start again. If the error persists call the 
      Duty Technician.
\item Test the performance of the encoders by running
      the task ENCODERS from the Telescope Control System terminal. Type:

 \PE{ENCODERS}

 This runs a program which compares the readings from the 4 independent 
 encoders (3~Ferranti, 1~Baldwin) on each axis.
 Firstly, look at the Ferranti readings. If one of these is 
 grossly different from other two on the same axis (and from the 
 the synchro), then that individual encoder is baulking. Confirm this 
 by looking at the counters in the CLIP Centre. Correct any 
 obvious problems (disconnected electronics). 
 If the problem persists run the
 INPSCF task (see section \ref{ch7:query}) and reset the appropriate encoder 
 weight to zero with variables WHAFE{\it n} and WDCFE{\it n} for Hour Angle 
 and Declination Ferranti head {\it n}, respectively. 
 Thus, to disable Hour Angle Ferranti Encoder number 2, do:

 \PE{INPSCF}

 \INPSCF{WHAFE2 0.0} 

 \INPSCF{END} 

 Note that this procedure only affects the running system - if, 
 for any reason, the TCS is stopped and then restarted you will 
 have to reset again the appropriate weights to zero.

 \item Now repeat the ZEROSET and SNAFU and try again. 
 
 \item If all of the Ferranti readings appear to be sensible, compare the 
  Baldwin+Ferranti values with those for the Ferrantis alone. If they 
  are more than a few arcseconds different, then the Baldwin encoder has 
  probably broken. It is easy to switch over to using Ferrantis only 
  in Declination (just set Task Common parameter JDCBW to zero using INPSCF).
  If the problem is with the Hour Angle encoder, better call out the
  Duty Technician in order to check out the encoder and adjust the servo
  constants.
\end{enumerate}
\end{itemize}

\subsection{The telescope runs away}

Do the following {\em in this order very quickly}, whilst watching the synchros:
%{\bf DO THE FOLLOWING IN THIS ORDER VERY QUICKLY, WHILST WATCHING THE
% SYNCHROS:} 
\begin{enumerate}
\item IF THE TELESCOPE IS NEAR A LIMIT, PRESS EMERGENCY STOP.
 
\item Else press the T/S DOME \button{STOP} button on the Control Desk. If this
      does not stop the telescope, then 
 
\item Select ENGINEERING MODE and if everything else fails, 
 
\item PRESS EMERGENCY STOP.
\end{enumerate} 
 
If pressing the T/S DOME \button{STOP} worked, then none of the main control 
software tasks have stopped, and the control system seems to be in order. Thus,
check the following possible causes:
\begin{itemize}
\item Did you slew to the right place? Check on the Information Display. 

\item Were you using the handset when the runaway occurred? If so, the 
      the cause may be a stuck contact. 

\item Did the runaway occur in quick or slow-motion drive? If it happened in
      quick motion, a stuck Baldwin encoder is a likely candidate. Check this
      by running the ENCODERS test task several times whilst moving the 
      telescope slowly in Engineering Mode with the Slow Motion clamps on. If 
      one of the Baldwin encoders is not updating, then remove it from 
      operation as decribed in the previous section.

\item Are the encoders reading correctly? Do the tests given in the previous
      section. If none of the encoders appears to be working, and especially 
      if they all show values very close to zero and do not increment 
      when the telescope is moved, yet all of the control software is 
      operational, the most likely faults are:

\begin{enumerate}
\item Catastrophic CAMAC failure. In this case {\bf none} of the Information 
      Display readouts give sensible values. However, if for example the focus
      is reading correctly, but none of the HA and Dec encoders works, then it
      is quite likely that:
\item No clock pulses are reaching the encoder modules. Call the Duty 
      Technician.
\end{enumerate}
\end{itemize}

\subsection{Autoguider Problems} \label{ch13:guider}
\begin{itemize}
\item {\bf Autoguider Panel does not respond.} 

Check TCS tasks AGBX and AUTOGUIDE. Type at the TCS console:

\PE{D(ISPLAY) M(EMORY)}

Are tasks AGBX and AUTOGUIDE present and active (A)? If not, cancel and restart
the relevant task with:

\PE{CA(NCEL) AGBX}

\PE{RESTART AGBX}

and similarly for AUTOGUIDE. Further, restart the task from the ADAM terminal
with:

\ADAM{AGBXINIT}


\item {\bf Interprocessor Link down?} 

Call the Duty Technician, or check TCS task IPL with:

\PE{D(ISPLAY) M(EMORY)}

If task IPL is not active (A) or absent, cancel and restart with:

\PE{CA(NCEL) IPL}

\PE{RESTART IPL}

Further, the link should be re-initialised from the ADAM terminal with:

\ADAM{IPLINIT}
\end{itemize}
\vfill
\eject 
