[education/kstars/edejouhanet-master-patch-35811] doc: Update doc/ekos-scheduler.docbook

[Eric Dejouhanet]

Git commit 34b2e5d3e3a19db455aed9f07927a67900aa3490 by Eric Dejouhanet.
Committed on 27/12/2021 at 18:09.
Pushed by edejouhanet into branch 'edejouhanet-master-patch-35811'.

Update doc/ekos-scheduler.docbook

M  +13   -4    doc/ekos-scheduler.docbook

https://invent.kde.org/education/kstars/commit/34b2e5d3e3a19db455aed9f07927a67900aa3490

diff --git a/doc/ekos-scheduler.docbook b/doc/ekos-scheduler.docbook
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             The 2nd step is handled by image processing applications such as <ulink url="https://pixinsight.com">PixInsight</ulink>, among others, and will not be the topic of discussion here. The first step can be accomplished in Ekos Scheduler where it creates a mosaic suitable for your equipment and in accordance with the desired field of view. Not only Ekos creates the mosaic panels for your target, but it also constructs the corresponding observatory jobs required to capture all the images. This greatly facilitates the logistics of capturing many images with different filters and calibration frames across a wide area of the sky.
         </para>
         <para>
-            Before starting the <guilabel>Mosaic Job Creator</guilabel> in Ekos Scheduler, you need to select a target and a sequence file. The Sequence File contains all the information necessary to capture an image including exposure time, filters, temperature setting, &etc; Check that all the observation job conditions, constraints, and startup/shutdown procedures are as per your requirements since these settings shall be copied to all the jobs generated by the Mosaic tool. You do not need to add a job with this information ; if you added jobs to the observation list previously, Ekos will ask you if you would want to keep them before inserting the mosaic jobs in the list.
+            The <guilabel>Mosaic Job Creator</guilabel> in the Ekos Scheduler will create multiple Scheduler jobs based on a central target. It requires that you select first one target and one sequence file. The Sequence File contains all the information necessary to capture an image including exposure time, filters, temperature setting, &etc, and that information will be used for each pane of the mosaic. Observation job conditions and constraints shall be assigned too, so check that they are as per your requirements. You may simply prepare a new job without adding it, or pick an existing job, as long as both target and sequence file fields are valid in the Scheduler form. If you added jobs to the observation list previously, Ekos will ask you if you would want to keep or remove them before inserting the mosaic jobs in the list.
         </para>
         <para>
-            Start the Mosaic Job Creator by clicking on the icon next to the <guibutton>Find</guibutton> button in Ekos Module. A new window will open with a left-side form and your target centered in a sky chart. For convenience, maximize that window. There is a help icon on the top left part of the sky chart. Move your mouse over it to display the latest documentation of the tool.
+            When your target and conditions are ready, start the Mosaic Job Creator by clicking on the icon next to the <guibutton>Find</guibutton> button in Ekos Module. A new window will open with a left-side form and your target centered in a sky chart. For convenience, maximize that window. There is a help icon on the top left part of the sky chart. Move your mouse over it to display the latest documentation of the tool.
         </para>
         <para>
-            On first use, you need to enter your equipment settings including your telescope focal length in addition to camera's width, height, and pixel dimensions. Finally, you need to enter the rotation of the camera with respect to north or the position angle. If you don't know this value, start Ekos and slew to your desired target then use the <link linkend="ekos-align">Align module</link> to solve the image and obtain the position angle.
+            On first use, you need to enter your equipment settings including your telescope focal length in addition to camera's width, height, and pixel dimensions. Finally, you need to enter the rotation of the camera with respect to north or the position angle. If Ekos is already started, you may retrieve optical information by clicking the <guibutton>Fetch</guibutton> to fill those fields automatically. However, if the camera rotation angle is unknown at that step, you will first need to use the <link linkend="ekos-align">Align module</link> to solve a field near the celestial equator in order to determine it precisely.
         </para>
         <para>
-            Next, enter the desired overlap and number of horizontal and vertical panels (⪚ 2x2, 3x3, &etc;). The sky chart will update automatically after a short time, with target FOV calculated given the number of panels and your camera's FOV. By default, the percentage of the overlap among images is 5%, but you can change this value to your desired value. If you need to move the mosaic, close the tool and select a new target in the Scheduler. When satisfied, set the frequency of alignment and focus steps during the mosaic execution, choose an output folder and accept the dialog. Ekos shall create an observation job and a corresponding customized sequence file for each panel. All the jobs shall be saved to an Ekos Scheduler List (<literal role="extension">.esl</literal>) file that you can load on any suitable observing night and it will pick off where you left.
+            Next, enter the desired <guilabel>overlap</guilabel> and number of horizontal and vertical <guilabel>mosaic grid</guilabel> panels (⪚ 2x2, 3x3, &etc;). The sky chart will update automatically after a short time, with target FOV calculated given the number of panels and your camera's FOV. By default, the percentage of the overlap among images is 5%, but you can change this value to your desired value. Changing the <guilabel>overlap</guilabel> will adjust the <guilabel>mosaic grid</guilabel> to cover the same area, while changing the <guilabel>mosaic grid</guilabel> will extend or shrink the mosaic area.
+        </para>
+        <para>
+            The large number on the grid rendering represents the order in which panes will be captured. The default S-shaped choice, that is, west-east then alternating high-low/low-high moves, ensures minimal movement of the mount during observation. Uncheck <guilabel>Minimum mount move</guilabel> to revert to west-east/high-low movement only.
+        </para>
+        <para>
+            If your mosaic is located close to a celestial pole, you may observe that rendered panes start rotating due to the raising declination. Use the <guilabel>overlap</guilabel> to ensure panes cover the desired frame extents properly. A large overlap will make frame stitching easier during post-processing, but will more panes to cover the desired extent. However, if you already know the minimal amount of sub-frames your rejection algorithm will use during post-processing, you may want to increase the overlap to attain that amount on the areas covered by multiple panes. For instance, a 4x4 mosaic grid with 75% overlap has 16 sub-frames covering the central intersection, which is enough for Windsorized Sigma rejection. Although the resulting stack does not have the same height on all parts of the final frame, this method gives you control on signal-to-noise ratio and allows you to provide context to your target while exposing a relatively low number of captures.
+        </para>
+        <para>
+            If you need to adjust the position of the mosaic, click on the view and drag the chart to recenter your target. When satisfied, set the frequency of alignment and focus steps during the mosaic execution, choose an output folder and accept the dialog. Ekos shall create an observation job and a corresponding customized sequence file for each panel. All the jobs shall be saved to an Ekos Scheduler List (<literal role="extension">.esl</literal>) file that you can load on any suitable observing night and it will pick off where you left.
         </para>
         <para>
             With Ekos Scheduler, multi-night imaging is greatly facilitated and creating super mosaics has never been so easy.