List of applicable products of this documentation OMEA 6M OMEA 6C OMEA 3M OMEA 3C OMEA 5M OMEA 5C OMEA 8M OMEA 8C 1 Camera installation Camera installation The camera works outdoor, it is weather‐tight. Warning, the system is not submersible: it is not a diving camera. Moreover, it will prevent all intrusion of insects, even the smallest one. The camera has no mechanical shutter and Sun’s heat does not cause loss of operation of the camera. Please do not install the camera near a pollution source (like a chimney). Give as much exposure as possible and avoid obstacles. It is advised to level the camera with respect to the ground. The camera has three anchors on the back, these three ISO M6 not thru threaded holes by 10 mm depth. Use the supplied screws to fix or equivalent stainless steel A4 or A2 screw. The following stand can be used to install the camera safely (this is an optional item, purchased on request) ...
Camera optical settings 1.2.1. OMEA 3x and OMEA 6x The focus of the lens with respect to the image sensor is factory tuned. It is not possible to perform focus changes from outside, for tightness reasons. F‐number is fixed set to its lowest value, F1.6 allowing very sensitive operation of the camera. This cannot be changed from outside. Sharpness may vary from center to edges, according to the lens design and lens manufacturing quality variations. Opening the dome is possible, but this will jeopardize inner camera dryness: some desiccants bags are installed inside the camera, and if the dome is opened, those bags must be replaced! Infrared light (>700 nm) is blocked. Pixel size is 2.2µm for OMEA 3x and OMEA 6x. 1.2.2. OMEA 8xx The tilt of the lens with respect to the image sensor is factory tuned. It is possible to perform focus changes remotely by using the RS232 link. ALCOR‐SYSTEM will provide to the user the best focus encoder count (from 900 to 1100 encoders steps) Some variation may occur around this value during the life of the camera. By the same link, F‐number can be user selected. The lowest F/ is F2.8 and must be used overnight. During the day F/5.6 or F/8 can be used. This can be set by PC software. Sharpness may vary from center to edges, according to the lens design and lens manufacturing quality variations. Opening the dome is possible, but this will jeopardize inner camera dryness: some desiccants bags are installed inside the camera, and if the dome is opened, those bags must be replaced! Infrared light (>680 nm) and UV light is blocked (<420 nm). Pixel size is 3.8µm. ...
Rear of USB camera Fig. 9 Connector Role Gender (camera side) Temperature / Humidity sensor Female 5 pins #1 Weather station module (optional) Male 7 pins Power connector and RS232 link Male 4 pins USB link Male 6 pins For more information about the pins of these connectors, please ask us. If Weather module is present, never touch with your fingers the 7 pins of the connector (Connector #1). 1.3.1 Temperature sensor and humidity connector (#1) It is a 5‐pin connector. The probe located at the end of the cord will be placed preferably in the shade, as far ...
In the end, the host PC sees the camera as a regular USB device, despite data goes throughout ethernet cable. The embedded Silex DS‐600 is designed to easily connect and share USB 3.0 and 2.0 devices over a network. Printers, Scanners, Disk Drives, Cameras, Card Readers, or virtually any other USB device can be enabled with network capability. It allows flexibility to place the USB device anywhere on the network instead of needing to be attached directly to the computer, and multiple users can access the USB device. It helps extending the distance from the camera to the PC. Alcor‐system did extensive tests that have proven good reliability of this device. The Gigabit USB High Throughput Device Server has an IP address to communicate with. NOTE: For Linux users, as date of June 2020, there is no free SDK to drive the camera throughout Ethernet to USB with this device server. 2 Software Latest camera software can be found in our web site: http://www.alcor‐system.com/us/AllSkyCamera/softwares.html System requirement and operating system Hardware requirement (Minimum) OMEA 3x/6x PC with AMD or Intel CPU, (with passmark index above 2000) o Intel Core i3‐4012Y @ 1.50GHz (passmark index : 2000) Hardware requirement (Minimum) OMEA 8x PC with AMD or Intel CPU, (with passmark index above 3000) o Intel Core i3‐2330E @ 2.20GHz (passmark index : 3000) 2 GB Memory ...
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Once the camera is selected, the exposures start immediately. Then, do not forget to check the "Auto Exposure" box after the first image has been displayed. It should be by default. For color camera, the raw image from color camera is a black and white, this is called Bayer pattern image. So the true color image shall be computed. Check the box “Color image from Bayer array” and set it to #4 for OMEA 3C/6C cameras and to number #3 for OMEA 8C. Only the color cameras have this option enabled, monochrome (black and white camera) does not. Maximum recommended gain is 250 for OMEA 3C/6C, the more the gain is high, and image quality will be jeopardized by image sensor readout noise. Going above these settings may jeopardize image quality due to high noise. Maximum recommended exposure is 30s OMEA 8x and 45s OMEA 3/6xx. Going above these exposures times may render visible star trailing due to Earth rotation. Then check “Circular fisheye” for the area to be used for computing automatic exposure time. The area used for auto exposure computation, is displayed in red in the image of the sky. ...
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This directory (and subdirectories) is created automatically by the software. It is set by default, as shown in the next image, i.e This PC > Documents > Skywatch, that translates into C:\Users\[Login name]\Documents\skywatch, where [login name] is the name used to log into your windows session. Fig. 45 The subdirectory AVI: contains the latest videos generated by the camera control software. The subdirectory DarkFrames: contains the images needed for camera hot pixels removal. All CPA files found there are tried by the software to find the best dark frame to be used to remove camera hot pixels. The subdirectory FTPData: contains the final JPEG image produced to be uploaded on user’s website The subdirectory FTPLog: contains the log files generated for each image transfer to the website. These logs help to find out issues when transferring files to user’s website. file The subdirectory HotpixelsList: contains the hotpixlist.cos used to make hot pixel corrections ...
This file can be automatically generated from a feature from this software (see next paragraph) Logs files subdirectory: contains the log files of the software, in which are written the software actions and events as a text file. This is for debugging purposes. A new file is created each time you startup the camera control software. The log file is enabled into the main’s software setup panel. The subdirectory Year_month_Day like 2016‐06‐14: contains image files that are saved automatically by the software as jpegs files or CPA/FITS files. The directory is used from noon to noon. For instance images created from 12:00 on May 10th 2010 till May 11th, 2010 at 11:59 will all be stored inside 2010_05_10 subdirectory. Camera exposure time and gain The software has two recording modes: 3.3.1 Manual mode The user enters the exposure time and gain as he wishes. No adjustment is made by the software. 3.3.2 Automatic mode ...
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quality. Production of hot pixels depends mainly on the temperature of the CCD camera that is bound to external temperature. More the camera is being used under conditions of high temperatures, more the number of hot pixels. Exposure time also affects strongly the number of hot pixels: the higher the exposure time, the higher the number of hot pixels. The following series of images is quite demonstrative: in case of a black and white camera, the pixels are white hot and occupy a single pixel. It is possible to confuse them with stars, but their existence in areas without light reflects an important problem of image quality. In the case of a color camera, the effects of hot pixels are even worse: they are strongly colored (red or green or blue), and the eye can detect them very quickly. The image quality is highly degraded, the image is filled with colorful hot pixels altering image rendition. It is therefore essential to correct these hot pixels using an “dark" master frame, and possibly complete the task with a list of pixels to fix. ...
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Fig. 51 Fig. 50 Without correction of "dark" and hot pixels With correction of "dark" and hot pixels The software performs hot pixels fixing in three ways: ‐ By subtracting a master dark frame. ‐ Local pixel correction from a list of hot pixels ‐ Automatic local hot pixel removal based on two parameters Activation of these corrections is achieved using the main camera control panel, camera tab, then on the based following checkboxes "Remove dark frame", “Hot pixel removal” on pixel list coordinates or / and "Automatic hot pixel removal" The master dark frame is located in this folder: ...
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This dark frame subtraction is performed through an optimization algorithm of the coefficient to be applied to the master dark frame image. If many files are present, the software will select the master dark frame that provides a result that is closest to 1.0. Fig. 53 The software scans the presence of files in the DarkFrames folder and will automatically pick up the most appropriate. This means that if the master dark frame was produced at a given temperature, a given exposure time and a given gain, the software is able to optimize the subtraction of the current image by the best dark frame, even if there were temperature changes. This is performed within a reasonable range of variation. It will be discussed later on the effects and validity of the dark master frame according to the variation of parameters. As there are still hot pixels that have non‐linear behavior and cannot be corrected by the dark master frame, correction using hot pixels list can be achieved, cleaning the image of hot pixels by its neighbors. Just check the box highlighted in the screenshot below. ...
Fig. 55 It contains a list of hot pixels to repair/fix. 3.4.1 Achieving master dark frame The files located into DarkFrames folder, whose fundamental purpose has been presented above, may, in some cases no longer be adapted to the current image shooting conditions (due to seasonal temperature changes). This is especially the temperature change that will determine the validity of the master "dark" frame. This validity is above/below 5°C the temperature where the master dark frame has been recorded. Beyond this temperature range, the image hot pixel repair/removal using this dark frame might become poor and not effective. For example, a master "dark" frame recorded from a set of some dark images at 20 ° C will be valid for images acquired between +15 °C to +25 °C. It is better to build a small library of "dark master" for each 5°C (outdoor temperature) The software will automatically select the most appropriate in the “DarkFrames” folder. How to make a master "dark" frame for a given outdoor temperature? This is easy. Under “Camera” tab, uncheck "Auto Exposure time" and select an exposure time corresponding to the longest exposure time used during night, for example 30s Concerning gain, the largest gain used during night, for instance 150 (and then "Apply") ...
Fig. 58 For each image recorded by the camera, the dark master frame file will be used in the form: Displayed_image = Raw_Image ‐ ( k * Master_dark_frame_Image) Where is a coefficient optimized by the software. More is close to 1, the better. In the following scenario, k = 0.95, which is a good value. Fig. 59 k> 1.5 k <0.5, it means that the master dark frame is not well appropriate to the current outdoor ...
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Fig. 60 The algorithm automatically eliminates hot pixels by inspecting all pixels from the incoming image. Two parameters to set two conditions are necessary. The first parameter defines the difference of the pixel compared to its eight neighbors for which that pixel will be considered as potential hot pixels because it exceeds the defined gap (as ADU). The second parameter sets the maximum standard deviation of the eight neighboring pixels, if the deviation is less than the defined value; the central pixel is considered as potential hot pixel. When the two above conditions are met, the hot pixel is fixed automatically. Fig. 61 The figure above shows that the automatic correction is performed on average into one pixel every 69x69 pixel box. To test this feature, use a moonless night, and be careful not to remove some stars of the picture by setting a too low maximum gap and too high standard deviation! ...
A pixel density corrected that implies one pixel every 7x7 pixels box is maximum, beyond this density, such as one pixel each 5x5 pixel, you will have to achieve your "dark" frame and the list of hot pixels bound to it. 3.5. Embedded Image Status information In JPEG image, a cartridge is indicating camera statuses, "2129" indicates the number of images taken since the software has been started up. "D 1.6" indicates a correction by a factor 1.6 of the dark frame; "H" indicates hot pixel correction using a list, for example "18x18 H" indicates that an average of one pixel of 18x18 pixel bow is repaired. If H! is displayed, this means that the hot pixel file was not found. The “L 9x9" indicates an automatic correction of hot pixels having an average density of 1 pixel per 9 by 9 pixels. Fig. 63 Fig. 64 Setting the overlay grid ...
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A camera gain reference Opening aperture reference (which is usually fixed as the aperture setting is not accessible). Subtracting the reference image by a master dark frame The camera gamma adjustment must be set to 100. Avoid the presence of Milky Way overhead. Save reference image as CPA / FITS Using this reference image, the signal is expressed as ADU. Nearby zenith the signal is measured and is reduced to a pixel, and must be entered in the panel from figure (Fig. 71) “Reference pixel signal” field. It is advisable to use image processing software (such as Prism or equivalent). At the time of reference image acquisition (during night), using a sky meter measuring device such as Sentinel or SkyQualityMeter (Unihedron), the magnitude per square second will be retrieved and entered as a reference “Reference Magnitude per arcsec²”. The coefficients "A" (0358) and "B" (0.004045) are specific to the camera law gain and might remain at their default values above, but can be re‐calibrated in laboratory for a specific camera. Once the calibration parameters known, the software calculates the magnitudes map per square second ...
Telescope control software link Telescope's pointing direction can be display and embedded to the last all Sky Image. The telescope pointing software shall be able to generate a simple text file, containing date and time of the measured position and equinox 2000 RA/DEC coming from the telescope current position. Current telescope position merged to the last all Sky image Fig. 73 If the time gap between the current date and the date of the last telescope position is greater than 10s, the telescope’s cross position switches to red color, indicating that the position is no longer refreshed by the software, and thus might not be valid. Telescope position as red because current date and telescope position date is larger than 10s Fig. 74 Here is the file format used to read telescope position as ASCII file, 1 line is amount of days since Dec 31 ...
4 Sphere condensation heater management Introduction The heating of the sphere is achieved throughout a set of resistors placed under the sphere base. It can defog or defrost the outside side of the acrylic sphere. The system is autonomous (works without link to PC and without user's supervision). It sets out the conditions when temperature and humidity levels enable occurrence of water condensation. As soon as the temperature is below a certain value, and moisture above another value, the heating system is automatically activated. These levels are named temperature and humidity levels. By default, factory set, the default threshold temperature is set to +7 ° C and humidity level to 90%. These thresholds may be inappropriate for a given site and can be adjusted by user input (RS 232 link to camera is mandatory to do so). Similarly, the heating power is set by default to 50%, it can be changed according to site and circumstances. Adjusting and start‐up Use the menu "Options / Dome Heating Control…" from the camera software main’s menu. Fig. 80 ...
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The next plot shows as red the external camera humidity, and the marron plot is the internal caùera humidity. The internal humidity shall be kept under 20% RH. The camera embeds a desiccant (molecular sieve) inside it, to have the humidity as low as possible, to prevent dew from forming in the inner side of the dome. So do not dismount the backside of the camera if not needed, this would cancel out the effect of the desiccant, and humidity level would be higher than 20% RH. Relative humidity plot, the orange arrow shows the inner humidity level of the camera. Here close to zero on a Fig. 84 brand‐new camera with fresh desiccant. The tab "Control/Setup" sets the temperature and the humidity threshold levels that will trigger sphere heating ...
The cable bringing power to the heaters should not be pinched during reassembly O‐rings properly positioned in their grooves The distance between the sphere support and the camera body must be at least 0.7mm and constant around the perimeter. 8 screws must be put together with their washer and all tightened the same way. Incorrect reassembly can cause loss of sealing, allowing rain to enter and de facto guarantees no longer apply. If you feel confident with dismounting sphere, please do not do it. 6.2 Camera internal desiccant replacement Inside the camera, a small desiccant bag has been installed. This is molecular sieve that can set the level of humidity down to zero. Replacement of this bag, may happen once every 3 years. The inside camera relative humidity can be monitored, if above 60% inside the camera, this latter should be inspected for leaks. 7 Trouble shooting This section aims at providing hints to solve issues. 7.1 Camera does not deliver images The USB port driver might be outdated, please update USB port driver. Also change USB port on your PC, sometime some USB are slightly damaged (ESD) with the course of the time. If the issue persists please contact us, the long 20 m USB extender cable might be also damaged, check that no damage has occurred on this cable (no small animal has started to eat the USB cable for instance, or ...
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