Information for Astronomers
Information for Astronomers
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As the computers in the observer building are connected to the MPIfR internal network, one can simply access the VNC by entering
vncviewer 134.104.70.120:99
into a unix terminal and then entering the password.
A window should appear with the VNC desktop. This is the telescope control computer "4mteleskop
".
4mteleskop
/home/operateure/
/home/operateure/start4m.sh
through any text editor../start4m.sh
This should open all the necessary windows to operate the telescope.4mcontrol.py
window with the blue input line is visible. This is from where you can control the telescope.The continuum backend measures the total flux coming from the telescope over the whole range of Frequencies received. It is usually used to quickly map out where radio sources are. It can be started by entering:
pbebackend('cmdusedchannels 1 1','cmdnumphases 1','cmdmode external','configure')
The Fast Fourier Transformer backend separates the signal from the telescope into its constituent frequencies. This allows the detection of physical processes radiating at distinct frequencies in specific regions of the sky. It can be started by entering:
fitwriter('band1:cmdnumspecchan 8192','band2:cmdnumspecchan 8192','cmdusedsections 1 1','cmdmode int','cmdsynctime 200000','cmdblanktime 2','cmdnumphases 1','configure')
In both cases the selection of the backend must be followed up by
send()
to actually send the command through the network to the appropriate devices. After this you can start the observation by entering
start_messung()
The telescope can only move within certain limits. These are: 0°-90° Elevation 0°-270° Azimuth Be careful not to let the telescope cross over these limits.
The commands for the telescope have several variables that you change for each command. If you leave out a variable, the control program will use the default value. (Mostly 0.)
Variable | Purpose | Default Value | Unit | Other |
---|---|---|---|---|
integration=None, | sets the time for collecting radio flux from the specified source | None=infinite | ms | 0 means no data collected |
offsetx=(offx,unitoffx), offsety=(offy,unitoffy), | sets an offset in az,el to point beside the given coordinates | 0, 0, | unitoffx and unitoffy in the format 'd' for degrees | can be used to fine tune pointing |
velaz=None, velel=None, | sets the velocity at which the telescope moves along the given axis | 'Schleichgang' | 'Schleichgang': slow, 'Eilgang': fast, 1: 1°/sec | velocity is calculated automatically for crosscans |
coorsys = 'J2000.0', | specifies in reference to which point in time the coordinates were given | 'J2000.0' | 'J2000.0' OR 'B1950' | |
lng = (l, unitl), br = (b, unitb), | sets the position of the telescope in galactic coordinates | 0, 0, | unitl and unitb in the format 'd' for degrees | |
ra = (rec, unitrec), dec = (decl, unitdec), | sets the position of the telescope in equatorial coordinates | 0, 0, | unitrec and unitdec in the format 'd' for degrees | |
el = (posel,unitel), az = (posaz,unitaz), | sets the position of the telescope in local coordinates | 0, 0, | unitel and unitaz in the format 'd' for degrees | with this option the telescope does not turn with the rotation of the earth |
messobjekt, | specifies which source to point towards | None | — | names looked up in in CDS name resolver |
lengthx = (lengthaz,unitlenx), lengthy = (lengthel,unitleny), | specifies the distance th telescope should move in az,el during a crossscan | 0, 0, | unitoffx and unitoffy in the format 'd' for degrees |
In order to point the telescope towards a specific heading - for example when shutting it down - you can use the command:
set_position_azel(integration = 0, el = (posel,unitel), offsety = (offy,unitoffy), az = (posaz,unitaz), offsetx = (offx,unitoffx), velaz = None, velel = None)
The correct shutdown position is Elevation: 35, Azimuth: 130,
In order to track an object across the sky, you can use the command:
track(messobjekt, integration = None, offsetx = (offx,unitoffx), offsety =(offy,unitoffy))
To detect the maximum intensity and precise position of sources, you can use the command:
crossscan(integration,messobjekt = None, az = (posaz,unitaz), el = (posel,unitel), lengthx = (lengthaz,unitlenx), lengthy = (lengthel,unitleny), offsetx = (offx,unitoffx), offsety =(offy,unitoffy))
The speed at which the telescope moves is determined by the integration time given, and the length given for the crossscan. The telescope will move to approximately to "position - 1/2 length" and then sweep over to approximately "position + 1/2 length" over the time frame given. It adds a couple of seconds of movement at the beginning and the end to avoid sudden jolts of the telescope.
The calibration diode is used to give a reference flux to determine the actual signal strength by comparing the incoming signal to it. For the time being it has to be turned on and off manuall at the start of each scan. This can be done via:
cal_on()
and
cal_off()
This indicates that the telescope control programs froze for some reason and need to be restarted. Close all windows by pressing Ctrl+C
or the X button. Restart the telescope control programs via ./start4m.sh
.
If a crossscan was started close to the hardcoded Azimuth endpoints of the telescope, it is possible that the telescope crossed over this endpoint. This means the actuator controls will have to be manually restarted by a technician.
This happens occasionally, and while the plotting windows can be a nuisance, the data is unaffected and measurements can continue normally.
First the validity of the password needs to be checked. If it is still not allowing a connection the wrong password may have been entered too many times, in which case a technician will need to restart the VNC server to reset the lockout.
If the telescope does not function due to a different error, you should contact a technician.