CRYOCAM    Frequently Asked Questions: -

Q1. The system seems to be running more slowly than I remember in the past and some of the modes donít seem to be quite right?

A1. This problem sometimes occurs after mode changes, particularly when someone attempts a mode change such as binning or windowing whilst reading out. The solution is to Ďexití both the control and display applications and restart by double clicking on the Cryocam icon.

Q2. The sky background appears to have pattern noise and this is particularly acute when using the fast readout 8-bit focus mode?

A2. On two occasions the body of the camera has been earthed through the mounting and this causes earth loops and pattern noise much the same as with any of our other CCDs. I believe this is problem has been addressed with design changes to the bracket. However, if this is suspected, simply close down the PC applications, switch off the camera at the PSU mounted on the telescope, remove both the D-type connector (power) and BNC coax connector (communication with PC) and check if the camera is electrically isolated from the telescope. The chrome fan guard is a good place to connect the meter on the camera. If the resistance is not infinity then you need to find out why. It is possible that paint has been abraded where the camera slides through the A&G mounting plate or the camera is earthing through itís bottom mounting screws.

On one occasion, I performed this check and discovered the camera was indeed isolated. I then played the usual CCD game of rearranging the cables went back to the control room and it was perfect. I have a suspicion that INGRID has a detrimental effect as I had not seen this problem before INGRID was mounted. The long cables supplied are very convenient for testing at the telescope, but I will arrange to have a shorter cable made up as this might improve the situation.

Q3. During afternoon checks when making a zero second integration (bias), I noticed light leaking at the centre of the field?

A3. I have noticed this once or twice, but fortunately not recently. The suggestion is that the shutter is not closing properly. To be quite honest, it doesnít seem to make very much difference on the sky. If smearing is noticed then it is better to limp through the night with a faster readout mode such as binning or focus and try to sort out the problem in the morning.

I believe this was caused when the camera moved on itís focus slide and collided with the boss at the centre of the filter wheel. Modifications made after this problem were noticed to prevent this from happening again.

Q4. The camera appears insensitive to light after a long run of faultless operation?

A4. I was once called up at night because of this problem. The TO confessed to using the camera for about 1.5 hours in near continuous operation, I think with a 1 second integration (probably not conducive to a long shutter life). I switched the camera to focus mode and went into the dome to listen if the shutter was operating. It sounded normal to my ears. When I tried to reach the shutter with my fingers (probably also not a good idea), I noticed that the front of the camera was much warmer than I would have expected. I switched off the camera for a maybe ten minutes (fortunately the observer was using UES at this time). When I switched on again, the system functioned normally.

On another occasion; fortunately during the day, I discovered the camera was again insensitive to light, but the shutter sounded normal. I simply switched off the camera for a few minutes, restarted the software and it worked!

My thoughts are that long continuous shutter operation might cause the moving part of the solenoid driving the shutter to expand and stick inside the bobbin, but my later experience made me think this just might be an electronics problem. I suggest you try switching off at the telescope for a few minutes before attempting anything that might result in more downtime.

Q5. One morning I wanted to do some work on the Cryocam, but noticed the loss of the communication message as soon as I started the software. I was pretty concerned since these were the symptoms that plagued the camera when it was first delivered a year earlier. I went into the dome and noticed the camera fan had stopped, but was twitching as if it were stuck. I switched off and removed the cables, unbolted the bracket and attempted to operate the camera in the control room with the shorter cables. Again it cooled down and functioned normally. I spoke to Microluminetics about this problem and they suggested a modification which I started to do, but then they hesitated. Anyway, the problem has not reoccurred.

Q6. The camera works fine, but are we going to get: -

A6. You should remember that the Cryocam is a commercial package and not developed in Cambridge, Durham or Edinburgh exclusively for ING. As such we have to accept what we have been given and my priority with this project has been to ensure that the system does everything the supplier says it should. Now the system seems to work reliably, it is possible that we could go back to Microluminetics with a list of software enhancements. So please let me have your ideas.

Q7. Will the video printer work with this system?

A7. In principle it could be made to work. That particular printer has a SVGA input, but itís still connected to the VME system. The Cryocam PC is networked to the WHT laser printer. Simply click on "print" in the ĎFileí pull-down menu and click on "print". There is no printer message, but a good quality print should pop out on the laser printer next door.

Q8. Can we export files into a data reduction computer and use packages such as IRAF?

A8. Yes. At the moment you should save the image as a fits file and then ftp it to one of the Sparc data reduction computers. There is some incompatibility between the file extensions (FIT to fts I think) and between upper and lower case names, but you can use the ftp application to make the conversion. Otherwise it works fine.



Clive  Jackman  10th September 2001