Git commit 323adaebb6b30b3b11428819a03dd1f5c92f0644 by Yuri Chornoivan. Committed on 30/11/2023 at 07:16. Pushed by yurchor into branch 'master'.
Fix minor typos M +7 -7 doc/ekos-capture.docbook https://invent.kde.org/education/kstars/-/commit/323adaebb6b30b3b11428819a03dd1f5c92f0644 diff --git a/doc/ekos-capture.docbook b/doc/ekos-capture.docbook index bbbf7ba139..4237c7268c 100644 --- a/doc/ekos-capture.docbook +++ b/doc/ekos-capture.docbook @@ -510,7 +510,7 @@ The implementation of this process does not consider the strength (magnitude or flux) of the intended target, nor does it consider other factors which may cause an astrophotographer to choose a alternate sub-exposure time. These other factors may include: the storage requirements and extended post-processing time for a large number of short exposures, the impacts of external factors that might occur in very long exposures, such as tracking / guiding performance, changes in weather conditions which may disrupt seeing conditions, intrusions from air traffic or passing satellites. </para> <para> -Approaches to imaging can vary greatly in the selection of exposure times, and number of sub-exposures used for integration. A well accepted approach for imaging deep-sky objects utilizes long exposures, requires good guiding, good to excellent seeing conditions, and would typically employ filtering to reduce the effects of light polution. At the other extreme are approaches such as speckle imaging techniques (commonly 'lucky imaging'), which utilize many hundreds to many thousands of extremely short exposures in an attempt to eliminate the effects of light pollution, poor seeing conditions, and poor guiding. Choices made for values of certain inputs to the exposure calculator will vary depending upon which imaging approach is being employed.</para> +Approaches to imaging can vary greatly in the selection of exposure times, and number of sub-exposures used for integration. A well accepted approach for imaging deep-sky objects utilizes long exposures, requires good guiding, good to excellent seeing conditions, and would typically employ filtering to reduce the effects of light pollution. At the other extreme are approaches such as speckle imaging techniques (commonly 'lucky imaging'), which utilize many hundreds to many thousands of extremely short exposures in an attempt to eliminate the effects of light pollution, poor seeing conditions, and poor guiding. Choices made for values of certain inputs to the exposure calculator will vary depending upon which imaging approach is being employed.</para> <orderedlist> <listitem> <para> @@ -522,10 +522,10 @@ Approaches to imaging can vary greatly in the selection of exposure times, and n <para>The range for Sky Quality is from 22 for the darkest skies, to 16 for the brightest (most light-polluted) skies. The magnitude scale is non-linear; it is a logarithmic scale based on the 5th root of 100. So 5 steps on the scale represent a change in brightness by a factor of 100. (A Sky Quality of 17 is 100 times as bright as a Sky Quality of 22. Each full integer step on the scale is a change by a factor of approximately 2.512.). <ulink url= "https://en.wikipedia.org/wiki/Light_pollution";>Wikipedia Sky Brightness</ulink> <ulink url= "https://en.wikipedia.org/wiki/Light_pollution";>Wikipedia Light Pollution</ulink></para> <para> - All light scattered in the backgound sky is considered to be light pollution regardless of its source, so the effects of moonlight should be considered as "natural" light pollution. But weather conditions can also impact Sky Quality, as humidity or cloud cover can reflect and scatter any source of light through the atmosphere</para> + All light scattered in the background sky is considered to be light pollution regardless of its source, so the effects of moonlight should be considered as "natural" light pollution. But weather conditions can also impact Sky Quality, as humidity or cloud cover can reflect and scatter any source of light through the atmosphere</para> <para> A <ulink url= "https://en.wikipedia.org/wiki/Sky_quality_meter";>Sky Quality Meter (SQM)</ulink> - can provide the most accurate reading of sky quality if used during an imaging session, but an estimated value from sky quality surveys may also be found on the web at sites such as <ulink url= "https://www.lightpollutionmap.info/";>www.lightpollutionmap.info</ulink> or <ulink url= "https://clearoutside.com/";>www.clearoutside.com</ulink>. But these on-line sources for estimated light pollution genearrly do not account for the effects of moonlight or local weather conditions. So the values from light pollution web sites should only be considered as a “best case scenario” for a cloudless night during a new moon.</para> + can provide the most accurate reading of sky quality if used during an imaging session, but an estimated value from sky quality surveys may also be found on the web at sites such as <ulink url= "https://www.lightpollutionmap.info/";>www.lightpollutionmap.info</ulink> or <ulink url= "https://clearoutside.com/";>www.clearoutside.com</ulink>. But these on-line sources for estimated light pollution generally do not account for the effects of moonlight or local weather conditions. So the values from light pollution web sites should only be considered as a “best case scenario” for a cloudless night during a new moon.</para> <para> If a light pollution map value is used for the input value of SQM, but imaging will be performed with a partial moon, then a decrease in the input of the SQM value should be applied in the calculator. Moonlight can be overwhelming; at a location where a light pollution map showed an SQM value of 19.63. An SQM reading was made on a night with a waxing crescent, shortly before half-moon, (moon age 5.4, and KStars moon magnitude = -10). The SQM reading at zenith showed the sky to be much brighter with measured value of 18.48. A reading taken on a night with a waxing gibbous, shortly before a full moon, (moon age 12.4, and KStars moon magnitude = -12). The SQM reading at zenith showed a measured SQM value of 15.95.</para> <para>The value of Sky Quality has a drastic impact on the calculated exposure because of the logarithmic scale involved. An image taken from a location with heavy light pollution (a low sky quality value), especially when filtering is not applied, may result in a very short exposure time to prevent light pollution from overwhelming the target signal. An image taken from a location with very little light pollution (a high Sky Quality value) may result in an sub-exposure time of several hours.</para> @@ -646,14 +646,14 @@ The value of image stacking is that as images are stacked, the accumulation of e <listitem> <para> <guimenuitem>Table</guimenuitem>: A table provides details for stacking based upon the number of hours planned for imaging.</para> -<para>The table provides a quick reference for finding the appoximate number of sub-exposures that might be completed for a given number of hours in a imaging session. But some functions that consume time are not included in this time calculation. For example, USB based cameras typically take some time for data transmission, or if the user has selected automatic dithering, additional time will be consumed in the imaging process, which is not included in this time calculation.</para> +<para>The table provides a quick reference for finding the approximate number of sub-exposures that might be completed for a given number of hours in a imaging session. But some functions that consume time are not included in this time calculation. For example, USB based cameras typically take some time for data transmission, or if the user has selected automatic dithering, additional time will be consumed in the imaging process, which is not included in this time calculation.</para> <para>The far right column of the table shows the calculated time/noise ratio of the integrated (stacked) image that would be produced.</para> </listitem> <listitem> <para> - <guimenuitem>Graph</guimenuitem>: An interactive graph allows the user to visualize the relative change in potential quality for integrated images with various counts of sub-exposures applied in image stacking. This graph can be navigated through the adjustment of the time/noise ratio value; adjusting this value will recompute the quantity of sub-exposures required for the integrated image to acheive that specified time/noise ratio.</para> + <guimenuitem>Graph</guimenuitem>: An interactive graph allows the user to visualize the relative change in potential quality for integrated images with various counts of sub-exposures applied in image stacking. This graph can be navigated through the adjustment of the time/noise ratio value; adjusting this value will recompute the quantity of sub-exposures required for the integrated image to achieve that specified time/noise ratio.</para> -<para>In the selection of a Time/Noise ratio for the calculation of the count of stacked exposures, the user might want consider the incremental change to the poterntial quailty of the image from an addtional sub-exposure. To help a user assess the value of increasing the number of sub-exposures for integration; the tool includes a calculaton of the slope for the selected point on the time/noise curve (the user interface uses a delta symbol to present this value). This delta value represents the change in potential quality that will result from the addition or subtraction of a single sub-exposure.</para> +<para>In the selection of a Time/Noise ratio for the calculation of the count of stacked exposures, the user might want consider the incremental change to the potential quality of the image from an additional sub-exposure. To help a user assess the value of increasing the number of sub-exposures for integration; the tool includes a calculation of the slope for the selected point on the time/noise curve (the user interface uses a delta symbol to present this value). This delta value represents the change in potential quality that will result from the addition or subtraction of a single sub-exposure.</para> <para>As one should expect, at the low-end of exposure counts (when a low value for the Time/Noise Ratio is input), the delta value will be relatively high, so the addition of one image will provide a relatively large improvement to the integrated image. But as a user increases the value for the Time/Noise Ratio, more images will be included for integration, and the delta value will fall, indicating that there is less to be gained from adding more sub-exposures. </para> @@ -683,7 +683,7 @@ Part of the value of using a Time/Noise ratio as the input for the calculation o <phrase>300 Second sub-exposure</phrase> </textobject> </mediaobject> -<para>For an integration using the 30 second sub-exposures we find that 637 sub-exposures would be required to achieve a time/noise ratio of 80. So a total integration time of 5.31 hours is required with these shorter exposures to acheive the same time/noise ratio in the integrated image.</para> +<para>For an integration using the 30 second sub-exposures we find that 637 sub-exposures would be required to achieve a time/noise ratio of 80. So a total integration time of 5.31 hours is required with these shorter exposures to achieve the same time/noise ratio in the integrated image.</para> <mediaobject> <imageobject> <imagedata fileref="exposurecalculation-example_subexp30.png" format="PNG"/>
