Differences

This shows you the differences between two versions of the page.

--- en:ost:fokus_new [2025/09/29 20:33] – [Focusing] rhainich
+++ en:ost:fokus_new [2025/10/09 08:37] (current) – [Using NINA] rhainich
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 | Canon + Superzoom         |  80     |  19550  |
-==== Manually ====
+===== Focus using the hand terminal =====
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 </WRAP>
-A hand-held terminal (<imgref handterminal>) is available for manual operation of the EFA. The hand-held terminal is located in the movable storage container in the dome. The hand terminal has to be mounted on the black control box labeled //Electronic Focusing Accessory// on the back of the telescope. The cable of the hand-held terminal needs to be plugged into the port labeled //H/C// (see <imgref focusser_box>), while the handheld terminal as such should be hung on a silver bolt in the direct vicinity of the control box. Please note that the handheld terminal is only relatively loosely attached to the bolt and therefore there is a risk that the hand terminal could fall off if the telescope is moved a lot. **If the hand terminal is mounted, control via the OMS is not possible**, therefore the hand terminal is usually not mounted to the telescope.
+A hand-held terminal (<imgref handterminal>) is available for manual operation of the EFA. The hand-held terminal is located in the movable storage container in the dome. The hand terminal has to be mounted on the black control box labeled //Electronic Focusing Accessory// on the back of the telescope. The cable of the hand-held terminal needs to be plugged into the port labeled //H/C// (see <imgref focusser_box>), while the handheld terminal as such should be hung on a silver bolt in the direct vicinity of the control box.  **If the hand terminal is mounted, control via the OMS is not possible**, therefore the hand terminal is usually not mounted to the telescope.
 <imgcaption handterminal_mounted|Back of the telescope with mounted hand terminal>{{ :ost:focusser:focusser_attached_1.png?300 }}</imgcaption>
 With the buttons ''In'' and ''Out'' of the hand terminal, the EFA can be moved in and out. The remaining buttons are for a derotator, which our telescope does not need. Therefore, these buttons are without function.
-==== Observatory Management System (OMS) ====
-The focusing by means of the OMS is done by the program //PWI3//, which besides focusing also controls the fans and the heaters installed in the telescope. The last two points are described in more detail in the article [[en:ost:tempregula|temperature regulation]].
+===== Observatory Management System (OMS) =====
+The focusing by means of the OMS is done by the program //PWI4//, which besides focusing also controls the fans and the heaters installed in the telescope. The last two points are described in more detail in the article [[en:ost:tempregula|temperature regulation]].
-{{ ost:software:pwi3_focus_2.png |PWI3: Focus window}}
+{{:ost:software:pwi4_focus_2.png?1000|PWI4: Focus window including temperature display}}
-The operation of the EFA is basically self-explanatory. The current position can be found in the field ''Focus Status'', while the EFA can be moved via the buttons ''IN'' and ''OUT''. From a drop-down menu, one can select ''Fast'', ''Slow'' and ''Increment'' for the speed. Using the ''GOTO'' menu, the EFA can be moved to a specific position.  An ongoing movement can be stopped at any time using the '' STOP '' button. The temporal course of the temperature of the main mirror, the support of the main mirror, the secondary mirror and the ambient temperature can be shown and hidden using the buttons ''SHOW'' and ''HIDE'', respectively.
-{{ ost:software:pwi3_focus_3.png |PWI3: Focus window including temperature display}}
+The operation of the EFA is basically self-explanatory. The current position can be found in the field ''Position'', while the EFA can be moved via the buttons ''IN'' and ''OUT''. The speed of the focuser can set under "Jog", by inputting a value next to it. We recommend the standard setting of 200 micron/s. Using the ''GOTO'' menu, the EFA can be moved to a specific position.  An ongoing movement can be stopped at any time using the '' STOP '' button. The temporal course of the temperature of the main mirror, the support of the main mirror, the secondary mirror and the ambient temperature can be shown and hidden using the buttons ''SHOW'' and ''HIDE'', respectively.
-=== Auto Focus ===
+==== Auto Focus ====
+In general it is not feasible to focus manually, unless a specific focus point is already known from e.g. previous observations. Therefore automatic focus methods can be found in several programs. Here we shall list focusing using PWI4, MaximDL, NINA and others. Whichever program is used depends on the observers preferences and target.
-//PWI3// also offers the possibility of automatic focusing. For this purpose, //PWI3// connects to [[en:ost:ccds:maximdl|MaximDL]] to take the necessary pictures. Hence, before starting the automatic focusing, the camera must be connected to //MaximDL//. With a click on ''AF CONFIG'' the settings can be adjusted. One of the most important settings is the ''Step Size (micron)'', which defines the step size in micrometers that the EFA should move at each focusing step. ''Steps (Image Count)'' is the number of focusing steps performed by the EFA and the number of images to be captured. The exposure time in seconds must be specified at ''Exposure length (sec)''. So far the following settings have proven to be useful:
+=== Using PWI 4 ===
+<WRAP center round important 60%>
+This part needs a revision.
+</WRAP>
+//PWI4// also offers the possibility of automatic focusing. For this purpose, //PWI4// can connect to //ASCOM// camera drivers. The corresponding setting can be changed in the ''Camera'' tab. In the ''AF CONFIG'' section the settings for the auto focus can be adjusted. One of the most important settings is the ''Step Size (micron)'', which defines the step size in micrometers that the EFA should move at each focusing step. ''Steps (Image Count)'' is the number of focusing steps performed by the EFA and the number of images to be captured. The exposure time in seconds must be specified at ''Exposure length (sec)''. So far the following settings have proven to be useful:
     Step Size (micron)    = 150
     Steps (Image Count)   = 17
-    Exposure length (sec) = must be chosen depending on the object
+    Exposure length (sec) = must be chosen depending on the object/filter (6s for stars using clear filter is a good start)
 {{ ost:software:maximdl:autofocus_good_3.png |}}
-After starting the auto focus, //PWI3// will perform the individual focusing steps, move the EFA by the ''Step Size'' and take one image at a time. Afterwards, //PWI3// will start the program //PlateSolve// (see above), which will analyze each image, search for stars, determine the diameter of these stars and estimate the focus. This is then listed in a table. With a click on ''Show Graph'' you can visualize the result. The determined star diameter is displayed over the position of the eyepiece extension. In the ideal case this representation follows a V-curve, which is also fitted into the data.
+After starting the auto focus, //PWI4// will perform the individual focusing steps, move the EFA by the ''Step Size'' and take one image at a time. Afterwards, //PWI4// will start the program //PlateSolve// (see above), which will analyze each image, search for stars, determine the diameter of these stars and estimate the focus. This is then listed in a table. With a click on ''Show Graph'' you can visualize the result. The determined star diameter is displayed over the position of the eyepiece extension. In the ideal case this representation follows a V-curve, which is also fitted into the data.
 In the following we show an example of a successful and an unsuccessful auto focus run:
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 There are several reasons why a autofocus run can fail. One of them is that the ideal focus is not in the area that is covered by the autofocus run. It is therefore recommended to focus the telescope roughly by hand before. Furthermore, it can be that no star is found and therefore the quality of the focus cannot be estimated. A reason for this may in turn be that the option ''Use a Subframe, Central 1/4 pixels'' was selected during setup and that there is no star in the central area of the chip.
-===== Using MaximDL =====
+=== Using MaximDL ===
-All our SBIG-CCD cameras can be controlled via //CCDOPS// as well as //MaximDL//. Here we will first concentrate on //MaximDL// before we deal with //CCDOPS// below. The most important functions of //MaximDL// have already been introduced in the main article on [[en:ost:ccds:maximdl|MaximDL]].
+<WRAP center round important 60%>
+This part needs to be written.
+</WRAP>
+=== Using NINA ===
+{{:ost:software:nina_autofocus_start.png?nolink&300 | NINA Autofocus}}
+In NINA the autofocus can be run by selecting ''Imaging'' and then select on the right-hand side autofocus. After selecting autofocus NINA will automatically start the process. Note however, that the focuser needs to be started via PWI4 and equipped via the "Equipment" tab. Furthermore NINA will use whatever filter is currently selected. A successful autofocus run can be seen on the left side, where a clear hyperbolic relation is visible. The run took about 6:30min and determined 6612 as the optimal focus for the clear filter.
+Under ''Options>Autofocus'' the settings to finetune the autofocus can be found. An image can be seen below the documentation of these settings:
+  * **Use filter offsets** lets you apply predefined offsets per filter instead of refocusing every time. (Currently not available, test observation needed). Default: OFF
+  * **Autofocus initial offset steps** determines how far the focuser moves out initially to start the autofocus. Default: 10
+  * **Autofocus method**: Self explanatory. Default: Star HFR (Half-Flux Radius of stars)
+  * **Curve fitting strategy**: Function to fit your measured data points. Default: Hyperbolic
+  * **Number of attempts**: How many times NINA retries autofocus if the first attempt fails. Default: 1
+  * **Use brightest n stars**: If >0, only the n brightest stars instead of all detected stars (Good for poor star fields/Noisy images). Default: 0
+  * **Outer crop ratio**: If 1 the overscan region is cropped. If -1 the overscan region will be included. Default: 1
+  * **Binning**: Pixel binning during autofocus. Default: 2×2
+  * **R² threshold**: Minimum quality fit for the autofocus curve before retrying. Default: 0.8
+  * **Autofocus step size** determines how far the focuser moves between samples. Default: 150
+  * **Default autofocus exposure time**: Exposure duration (in seconds) per autofocus frame. Default: 6s. Needs to be adapted for other filters.
+  * **Disable guiding during AF**: Turns off guiding while autofocus runs. Default: off
+  * **Focuser settle time**: Delay after a focuser move to allow mechanical settling. Default: 1
+  * **Number of exposures per point**: How many frames are taken at each step, then averaged. Default: 1
+  * **Inner crop ratio**: Ratio of the frame that is used for detecting stars. Default: 0.5 = 50%. Can be selected within [0.2,1]
+  * **Backlash compensation method**: Method used to cancel gear play. Available are ''Overshoot'' and ''Disable''. Default: Not available/Overshoot.
+  * **Backlash IN/OUT**: Step count used to clear backlash when moving in or out. Default: 20,0
+{{ :ost:software:nina_autofocus_options.png?nolink&1200 |}}
+==== The traditional approach ====
+The traditional method of focusing involves looking at an area of the sky containing a large number of closely packed stars, such as a globular cluster. These conditions make it easy to judge the quality of the focus by determining the focus position that allows you to resolve most of those closely packed stars.
+=== Using MaximDL ===
+<WRAP center round important 60%>
+This part needs a revision.
+</WRAP>
-The best way to focus is to use the //Exposure Preset// ''Focus'', which can be selected via the corresponding drop-down menu in the //Exposure Tab// of the //Camera Control// window (see below). In this preset many settings, important for focusing, are already pre-selected. In the examples shown below the exposure time (''Seconds'') is set to one second, this must be adjusted according to the object used for focusing.
+In the //Exposure Tab// of the //Camera Control// window (see below), select ''Focus'' in the //Exposure Preset// drop-down menu (see below). In this preset many settings, important for focusing, are already pre-selected. In the examples shown below the exposure time (''Seconds'') is set to one second, this must be adjusted according to the object used for focusing.
 {{ ost:software:maximdl:focus_maximdl_1.png |}}
-After a click on ''Start'' images are continuously taken and displayed. Now the telescope can be focused by means of //CW3// or the hand terminal of the EFA. To find the coarse focus, it is recommended to first approach a bright star and to focus in such a way that the diffraction ring disappears. Rough values for the focus with the different instruments and eyepieces can be found in the table above.
+After a click on ''Start'' images are continuously taken and displayed. Now the telescope can be focused by means of //PWI4// or the hand terminal of the EFA. To find the coarse focus, it is recommended to first approach a bright star and to focus in such a way that the diffraction ring disappears. Rough values for the focus with the different instruments and eyepieces can be found in the table above.
 In order to further optimize the focus, a globular cluster can be observed. The low angular distance between the stars in a globular cluster facilitates very good focusing results, since the Airy discs of the individual stars can only be separated with a very well focused telescope. An optimally focused telescope operates with a seeing limited resolution, which for our site is often larger than 2“. This is significantly worse than the diffraction limited resolution of our telescope, which is 0.23″. The [[https://de.wikipedia.org/wiki/Rayleigh-Kriterium|Rayleigh criterion]] describes the theoretical limit at which two Airy discs can be recognized as separated light sources.
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 The middle panel again summarizes the current information about the camera, e.g. if a image acquisition is currently running, which exposure time is set, the selected filter, if the cooling is running and if so, the current and target temperature of the sensor.
-==== Subframes ====
+== Subframes ==
 Subframes offer the possibility to significantly speed up the process of finding the optimal settings for the focus. By reading out only a small area of the CCD, which can be selected by the user, the readout time and also the download time can be greatly reduced.
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 **ToDO: replace images!**
+/*
 ===== Ussing CCDOPS =====
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 </WRAP>
 </WRAP>
+*/
 ===== Focusing aids =====