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cso:instruments:heterodyne:onoff [2013-11-14 03:05]
sradford created
cso:instruments:heterodyne:onoff [2014-04-09 21:33] (current)
sradford
Line 1: Line 1:
 +====== Position Switching ======
  
 +Single dish observations are explicitly differential:​ the signal from the On position (target+sky) is compared with the signal from the Off position (sky only). In position switching, the telescope points back and forth between the target and a nearby blank sky position.
 +
 +==== UIP commands ====
 +
 +  - Position switching with reference positions 300 arcsec (5 arcmin) away in azimuth. \\ ''​__uip__>​ **oo_scan //N// /step 300 /altaz** ''​
 +    * The telescope will move symmetrically \\ ''​+OFF ON ON -OFF''​
 +    * //N// is the number of repetitions of this pattern. ​
 +    * Because the sky brightness does not change, moving in azimuth results in better subtraction.
 +  - Position switching with reference position chosen to avoid emission regions, etc. \\ ''​__uip__>​ **oo_scan //N// /​designated_off ** ''​
 +    * The telescope will move asymmetrically \\ ''​OFF ON''​
 +    * //N// is the number of repetitions of this pattern. ​
 +    * The reference position must be specified in the source [[cso:​telescope:​uip:​catalog|catalog]] as //​target//:​off_position.
 +
 +There are other possibilities. For details, consult the online help, \\ ''​uip>​ ** help oo_scan ** ''​
 +
 +==== Caveats ====
 +
 +  * If the [[cso:​telescope:​secondary]] is wobbling, it will be stopped before an ''​oo''​ scan, then restarted.
cso/instruments/heterodyne/onoff.txt · Last modified: 2014-04-09 21:33 by sradford
 
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