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--- howto:focus [2009/05/02 18:33] – pkubanek
+++ howto:focus [Unknown date] (current) – external edit (Unknown date) 127.0.0.1
@@ Line 1: / Line 1: @@
+====== Focuser API ======
+Focuser presents various variables to the end user. They may look confusing on a first look, so here is a small description. You may find it also in //man rts2-focusd//.
+  * **FOC_POS** This variable show actual focuser position. If set, it will cause focuser to move to set position. If focuser is moved to position, it shows the actual focuser position.
+  * **FOC_TAR** Focuser target position. This shows desired focuser position. If set, it will cause to move focuser to set position.
+  * **FOC_DEF** Default focuser position. This is used together with FOC_FOFF and FOC_TOFF for autofocusing. If it is changed, target position is set to sum of **FOC_DEF**, **FOC_FOFF** and **FOC_TOFF**.
+  * **FOC_FOFF** Focuser offset found during focusing. This is used to temporary shift focus. If focuser driver is restarted, it is moved back to **FOC_DEF** position.
+  * **FOC_TOFF** Focuser temporar offset used during focusing. You should use this variable during focusing script to probe focus at different offsets.
+If your focuser is named **F0**, and you would like to probe focusing range 100 steps bellow to 100 steps above default focuser position, the focusing script should look like:
+  F0.FOC_TOFF=-100 for 20 { E 10 F0.FOC_TOFF+=10 }
+When script is finished, RTS2 will change **FOC_TOFF** to 0, which will cause focuser to move to default value. You can change either **FOC_FOFF**
+or **FOC_DEF** to set new focusing position.
+The following equation should be true when you change focus with **FOC_DEF**, **FOC_FOFF** and **FOC_TOFF**:
+  FOC_TAR = FOC_DEF + FOC_FOFF + FOC_TOFF
 ====== Focusing in RTS2 ======
@@ Line 31: / Line 52: @@
 A working solution is to set up the object detection (with ''detect.advanced'' ) so that it tries to determine the optimum aperture and stores it in the fits image keyword ''DET_APE''. ''detect.advanced'' normally does this, so just make sure that it is used. If you use ''detect.sexonly'' to gain speed, you may restrict detect.advanced only to the focusing target.
-Automatic focusing in RTS2 is solved using a combination of a observation scripts and observation processing. In particular, there is a special target which needs to be executed in order to (re)focus the telescope.
+Automatic focusing in RTS2 is solved using a combination of observation scripts and observation processing. In particular, there is a special target which needs to be executed in order to (re)focus the telescope.
 === Getting the minima ===
@@ Line 42: / Line 63: @@
 and if linear is not the best, the best fit of these three
 functions is proposed as a solution.
 ==== obs_process integration ====
@@ Line 78: / Line 98: @@
 === set the position ===
-To set the position computed from the data, one has to execute the following command:
+To set the position computed from the data, one has to execute the following commands:
   ''rts2-xmlrpcclient -s <FOCUSER> FOC_DEF <POSITION>''
+  ''rts2-xmlrpcclient -s <FOCUSER> FOC_TAR <POSITION>''
 The other imaginable ways like ''rts2-scriptexec -d <CAMERA> -s "FO.FOC_DEF=<position>"'' works as well, but XML-RPC interface is the prefered way how to solve the problem.
@@ Line 100: / Line 121: @@
   * the way of feeding back the computed position is not definitively solved
-  * there was bug related to scheduling of a command to move the focuser, which resulted in incorrect values in the fits headers. (i have no idea if this is already solved or it just happens randomly)
+  * there was a bug related to scheduling of a command to move the focuser, which resulted in incorrect values in the fits headers. (i have no idea if this is already solved or it just happens randomly)
   * we do not care if the astrometry is successfull, but obsproc mechanism by default does and does not provide a way to give us all images without complications. Disabling the astrometry and performing only object detection would improve the speed and overall processing.  -> disable the astrometry in the processing script? -> How many things would this break?