Usage of OCELOT on the RCC

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Contents

Using OCELOT

OCELOT itself can be controlled via a GUI, therefore the optimal way to reach the controlling computer (in case of the RCC) m16 is by VNC protocol, e.g.:

xvncviewer -bgr233 -via root@m16 :42

m16 can only be reached from the internal network. Screen 42 should be used. The switch bgr233 reduces the color depth resulting in lower latency.

On m16, the program ixon-server should always be running. Usually, the user does not have to start it. In case of a power failure, or software crash, it can be started with the command (via screen)

ixon-server /usr/local/etc/ixon-server/ixon-server.cfg

If the ixon-server cannot be started this way due to a lock-file in /tmp, but you are absolutely sure that the server is not running (try e.g. ps aux | grep ixon-server), the lock file can safely be removed. After the removal, the server will likely start. This problem is usually present if the ixon-server suddenly halts (i.e. not properly shut down), mostly due to a power failure, or a rare case of segmentation fault.

Before restarting m16, the ixon-server has to be stopped properly. It can be carried out via telnet:

telnet localhost 32768

After connecting to the server, the command shutdown stops the server itself. The connection can be terminated by closeconn. Do this only, if you are absolutely sure about the results!

The camera controlling program can be started by the following command:

ixon-gui

The FITS viewing program DS9 has to be started by the user as well. A typical screen of ixon-gui can be seen below.

A typical EMCCD session.

First of all, the connection can be established by pressing the Connect button at the lower-left corner of the window. The camera cooling can be controlled via the the Set Temp input field. Note that the power usage of the cooler is not indicated explicitly. If the current temperature is indicated by blue numbers, then the temperature set can be hold safely. Without the water cooler, a temperature of \approx -80^{\circ}\mathrm{C} can be reached. In wintertime, when the external temperature in the dome is below \approx 5^{\circ}\mathrm{C}, and the Case Fan is set to operate between 9.0-19.0^\circ \mathrm{C}, a stable -90^\circ \mathrm{C} temperature can be reached with air cooling. With the circulatory system installed, the threshold is around -100^{\circ}\mathrm{C}.

On the CCD Readout Control section on the above figre typical settings are shown. Change these only if you are certain about what you are doing!

The camera can be used in non-EM mode as well, in this case, the Output Amp field should be set to Conventional. Otherwise, set it to EM. The typical value of the EM gain is 40.

For dark frames, the field Shutter mode should be set to closed. The exposure time is given in milliseconds. Also note that the lowest achievable time depends on the trimming (it can be set in the input fields Image Size) and the binning. 2x2 binning is resonable to use in most cases. While doing lucky imaging 1x1 binning might be a better choice.

Observing sequences can be defined on the panel Observing Blocks in a self-explanatory way. In the ixon-gui, the filter field should be left on U. The filters can be set via the program acectrl running on m5. In the spectrograph frontend, there are two built-in filter wheels.

Filters

Currently a 80x80mm Johnson-Cousins BVRI set is installed at the first (#1) wheel while a partial series of 50x50mm Sloan filters are installed in the second (#2) wheel. The filters can be changed and specified in ixon-gui on the Observing blocks panel, or with the following command from the terminal:

acectrl --filter-1 n

where n indicates the number of the filter:

 - 0: empty     
 - 1: B         
 - 2: V         
 - 3: R         
 - 4: I         
 - 5: clear 

The second wheel can be changed accordingly, i.e.

acectrl --filter-2 n

where n indicates the number of the filter:

 - 0: empty     
 - 1: empty        
 - 2: empty     
 - 3: Sloan r'     
 - 4: Sloan i'  
 - 5: Sloan z' 

For a more detailed description of acectrl, see article ACE spectrograph.

Please note that the two filter wheels located above each other. Hence, one should set the second wheel to "empty" state if a filter from the first wheel is used and vice versa. Note that acectrl is a low-level control program in this sense. Using ixon-gui, this is done automatically.

Focus

Note that the focus of the telescope can be adjusted from ccdsh on the regular way:

set focus n

where n is the focus value. For the EMCCD/OCELOT, the default is around 79.8 without the Barlow lens.

Flat fielding

The following two tables contain some guidance for setting exposure times of flat field images. Note however, that at Piszkéstető, the observer always has to assume that the flat lamps have been moved (due to demonic possession, events only relevant on quantum levels, etc.), despite the large sign on the lamps saying "do not move the flat lamps, in fact do not even think about it". Therefore, these values have to be confirmed before a long sequence of flat field images.

Table for T=-70 C, AD converter setting 16bit, 1024x1024px image size, 1x1 bin. The pixel values are in the interval of 20k-40k ADU.

Conventional (bright) Conventional (faint) EM=5 (bright) EM=5 (faint) EM=20 (bright) EM=20 (faint)
Johnson B 45 - 35 - 10 180
Johnson V 5 60 5 60 1 15
Johson R 1 15 1 10 0.3 3
Johnson I 0.3 3 0.3 3 0.1 1
Sloan r' 1 15 1 10 0.3 3
Sloan i' 0.5 5 0.3 4 0.1 1
Sloan z' 0.5 5 0.3 3 0.1 1
Clear 0.2 2 0.2 2 0.1 0.5
Empty 0.2 2 0.2 2 0.1 0.5

Table for T=-70 C, AD converter setting 16bit, 1024x1024px image size, 2x2 bin. The pixel values are in the interval of 20k-40k ADU.

Conventional (bright) Conventional (faint) EM=5 (bright) EM=5 (faint) EM=20 (bright) EM=20 (faint)
Johnson B 15 120 10 120 - 45
Johnson V 2 20 1 15 - 5
Johnson R 0.5 3 0.3 13 - 1
Johnson I 0.1 1 0.1 1 - 0.2
Sloan r' 0.3 3 0.3 3 - 1
Sloan i' 0.1 1 0.1 1 - 0.3
Sloan z' 0.1 1 0.1 1 - 0.3
Clear 0.05 0.5 0.05 0.3 - 0.1
Empty 0.05 0.5 0.05 0.3 - 0.1
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