howto:focus
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- | ====== RTS2 and Autofocus | + | ====== |
+ | |||
+ | 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** 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, | ||
+ | or **FOC_DEF** to set new focusing position. | ||
+ | |||
+ | The following equation should be true when you change focus with **FOC_DEF**, | ||
+ | FOC_TAR = FOC_DEF + FOC_FOFF + FOC_TOFF | ||
+ | |||
+ | ====== Focusing in RTS2 ====== | ||
There is no discussion about the fact, that the correct focus is essential in obtaining a high-quality images. Normally, it is the responsability of the observer to keep the telescope well focused. In RTS2, however, the observer is replaced by a computer program, so also the focusing should be, optimally, solved by an automat. | There is no discussion about the fact, that the correct focus is essential in obtaining a high-quality images. Normally, it is the responsability of the observer to keep the telescope well focused. In RTS2, however, the observer is replaced by a computer program, so also the focusing should be, optimally, solved by an automat. | ||
- | The focusing subsytem is not yet definitively solved, but we have got already very far while solving this issue. | + | ===== Manual focus ===== |
+ | |||
+ | There are two ways of getting the telescope focused in the manual way - with and without looking at the actual image. | ||
+ | |||
+ | ==== rts2-(x)focusc ==== | ||
+ | |||
+ | A direct camera-to-image display tool is '' | ||
+ | |||
+ | Where the screen is not available, '' | ||
+ | |||
+ | Technically, | ||
+ | |||
+ | ===== RTS2 and Autofocus ===== | ||
+ | |||
+ | {{ :howto:focusing.png? | ||
+ | |||
+ | The autofocus | ||
- | ===== Search of FWHM minima | + | ==== Search of FWHM minima ==== |
- | ==== Getting the FWHM ==== | + | === Getting the FWHM === |
Images in RTS2 are normally processed using ''/ | Images in RTS2 are normally processed using ''/ | ||
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A working solution is to set up the object detection (with '' | A working solution is to set up the object detection (with '' | ||
- | 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 | + | === Getting the minima === |
The search for minima is executed from ''/ | The search for minima is executed from ''/ | ||
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and if linear is not the best, the best fit of these three | and if linear is not the best, the best fit of these three | ||
functions is proposed as a solution. | functions is proposed as a solution. | ||
+ | ==== obs_process integration ==== | ||
- | ===== obs_process integration ===== | + | === set up a focusing target === |
- | + | ||
- | ==== set up a focusing target | + | |
We are using NGC188 as a high | We are using NGC188 as a high | ||
density spot on the sky which is always accessible on the | density spot on the sky which is always accessible on the | ||
- | north. | + | north. |
- | '' | + | |
the known good focus position may be set upon start of this | the known good focus position may be set upon start of this | ||
- | script, (focpos=3500) to make sure the focus will always start | + | script, (F0.FOC_DEF=3500) to make sure the focus will always start |
at a reasonable place - even when the previous focusing run | at a reasonable place - even when the previous focusing run | ||
failed and provided a stupid position. Now it was not there | failed and provided a stupid position. Now it was not there | ||
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- in my case to construct a temperature/ | - in my case to construct a temperature/ | ||
- | ==== img_process | + | === img_process === |
If the local imgprocess calls '' | If the local imgprocess calls '' | ||
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predicted scatter into the fits keyword '' | predicted scatter into the fits keyword '' | ||
- | ==== obsproc.sh | + | === obsproc.sh === |
- | make sure an obsproc.sh gets called | + | ''/ |
- | calls the foc/src/script | + | |
- | command line. | + | |
- | ==== on-target focusing | + | === set the position === |
+ | |||
+ | To set the position computed from the data, one has to execute the following commands: | ||
+ | |||
+ | '' | ||
+ | '' | ||
+ | |||
+ | The other imaginable ways like '' | ||
+ | |||
+ | === on-target focusing === | ||
If anyone wants to reach a perfect focus for a particular target, then he has no other option than doing that manually as described above (i.e. setting up this target completely same as the special above PLUS the exposures needed to perform the observation -- which is for sure annoying), | If anyone wants to reach a perfect focus for a particular target, then he has no other option than doing that manually as described above (i.e. setting up this target completely same as the special above PLUS the exposures needed to perform the observation -- which is for sure annoying), | ||
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Generally, we have no telescope which would have the optic unstable enough to care about on-target focusing. | Generally, we have no telescope which would have the optic unstable enough to care about on-target focusing. | ||
- | ===== Known Issues ===== | + | ==== Known Issues ==== |
- | + | ||
- | * there is no way to feed the position back to the system FIXME | + | |
- | + | ||
- | * 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) | + | |
- | + | ||
- | * we do not care if astrometry is successfull, | + | |
+ | * the way of feeding back the computed position is not definitively solved | ||
+ | * 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, |
howto/focus.1234959832.txt.gz · Last modified: 2009/02/18 00:00 (external edit)