Artemis Capture user manual
Contents
1. Focus Assist When taking an astronomical image it is critical that focussing be as accurate as possible To help achieve this ArtemisCapture provides the Focus Assist dialog When you have the camera roughly focussed so that you can see stars in the captured im age you can activate the focus assist dialog by double clicking on a star For best results you need to choose one which is bright but not overexposed and which has a relatively clear area around it The program will select the brightest star in the vicinity of the selection and draw a small box around it It will also pop up a dialog showing some information about the star s image in a large bold font so that you can read it when at the telescope which may be some distance from the PC monitor The information provided is the star s maximum brightness the difference between the brightest pixel and the background level and the width of the star image This is calculated as the size of a square centred on the star s centroid containing half the total flux from the star The objective is to adjust the telescope s focus until the brightness reaches a maximum and the width reaches a minimum this will give the sharpest and brightest star images Whilst focussing it is also a good idea to select a sub Focus Assist frame around the star in order to reduce the image Bri 24044 download time and use the zoom feature so that the star is displayed highly magnified so you ca2. box will add a reticle to the displayed image It may be of use for determin ing the center of the frame so that you can align your goto telescope for example The Negative checkbox will display the image as a negative which can be useful when try ing to spot faint objects on a dark background Page 4 The Correct aspect ratio box adjusts the displayed image according to the physical dimen sions of the pixels on the CCD sensor If the box is checked then the height of the Capia yat image is scaled so that a square area on the screen corre oa sponds with a square area in the sky Display Black 2 _ _ Night Vision changes the Windows colors to shades of red in order to help preserve visual dark adaptation when using the sale 5525 program at night When the program shuts down or the box 4 oO _ is unchecked the original colors are restored Hint You can Zoom fp save the night vision color scheme for use with other programs if you click the checkbox and then right click the Windows Auto stretch Reticle desktop select Properties Appearance and then Save as Negative Give the scheme a name such as NightVision and you can Correct aspect ratio then return to it any time you like using this dialog You may Night vision DK also want to save your standard color scheme so that you can re select it after using the NightVision scheme The Dialog box
3. e next exposure Camera Subframe or the red square toolbar button allow you to drag an imaging sub frame using the left mouse button which is normally used to scroll the display You can always use the right mouse button to create a sub frame The green square toolbar button or the Camera Fullframe option will revert to using the full CCD area for imaging Camera Rotate 180 will rotate captured images 180 degrees This also rotates the saved image Camera Info gives some details of the Atik camera Camera Connect and Camera Disconnect will connect or disconnect the Atik camera File Fits header allows you to specify the target object telescope and observer name for recording in the header of saved FITs files The Quick menu options allow you to take an instant snapshot at a variety of exposures and binning levels with a single click or keypress Page 8
4. formed and at the bot tom are buttons for dealing with files To import a file click the Import button and locate a FITs file produced by a colour camera The name of the file will appear in the list box on the left and the image will appear in the preview window It may not look quite right at this stage The Delete button can be used to Page 6 ArtamilahtGe Sensor RGR Bits i Olisi 1 Oise o coLPF 1 umno ae afk Deb erates i ArtemisRGB screen remove an image from the list it does not delete it from the hard disk At the top left is a combo box where you can select whether to view the raw colour or lumi nance image The raw image will show you the checkerboard matrix pattern but for now we want to see the colour image Below this combo box is another one in which you can select whether the CCD uses a primary RGB or secondary CYMG matrix The ATK 16HRC uses an RGB matrix the ATK 16C uses a CYMG matrix Choose the appropriate one for your camera If you saved the file from a recent version of ArtemisCapture the colours should already be correct Otherwise you can try adjusting the X and Y offset values which tell ArtemisRGB where on the matrix the top left corner of the image lies For a full screen image in the standard ori entation these values ought to be 0 0 but if the image has been rotated or flipped then the values will need adjusting With a b
5. it of trial and error you should find values that give the correct colours Most deep sky targets are very faint and beacuse ArtemisRBG doesn t have any histogram stretching tools a Brightness selection is available which will allow you to increase the image brightness This will help to better see the object in the image but won t change the image in any way since it s for display purposes only Because some information is lost when the CCD samples the signal into different colours reconstructing the full colour image can sometimes introduce colours which weren t present in the original scene These are typically seen in regions of high contrast To help reduce these false colour artifacts you can run a low pass filter blur on the colour channel Then to restore sharpness to the image you can run a high pass filter sharpen on the luminance channel If you have multiple images loaded into ArtemisRGB you can give each one its own set of processing options if you need to In particular if some images were saved from a subframe then you may need to give them different X or Y offsets If you make a multiple selection in the image list the controls at the top of the program will indicate any values which are common to all selected images If values differ between images then they will be displayed as in the controls Changing any value will update that value in all selected images this can be a quick way to set the proces
6. n BATIK E E E E iNsTRUM ENTS Artemis Capture user manual Version 1 1 January 2006 Page 1 Introduction ArtemisCapture is a standalone program which allows you to control your Atik 16 camera take images preview them and save them to standard FITs files It does not perform any image processing other than simple histogram manipulation for mapping the 16 bit images to the display The data saved in the FITs file is exactly what is read from the camera raw so any adjust ment is purely for display purposes Features The capabilities of ArtemisCapture include Control over exposure time from 1milisecond 0 0001s upwards Control over pixel binning Selection of an image sub frame for rapid focusing Automatic capture of a series of images saved with sequential file names Adjustment of black and white levels and log stretch for displaying images Focus Assist option using data gathered from star images Zoom feature Display adjusted for aspect ratio for sensor whose pixels aren t square Night vision mode Using ArtemisCapture Tare ee I P Epit mna nie a eet t omy i o State 0 State 0 wich ie Hrd EE Full jii E amoa dung acou E In Car Precharge Subsi D Alo Pechrge Figh Poty M Aiae brga Biter E Diir dred ae Aa i its oun rh k Higi foun 1 ich The main Screen When you first start the program you will be warned if your A
7. n verify Wid 0 74 that the image quality is improving as you adjust the OK focus Then use the camera loop button to repeatedly Set OK take images until you reach perfect focus as indicated visually and with the Focus Assist dialog l Focus assist box Artemis Capture tracks the star from one exposure to the next by searching for the brightest pixel in the area around the star s previous location Depending on the magnification and stability of the telescope the star may drift by a number of pixels from its previous location Clicking the Page 5 Set button in the Focus Assist dialog allows you to specify how many pixels the program will search around the previous location when trying to locate the star You can also specify the radius that will be used to measure the star s properties once it is located this should be a little larger than the radius of the star but smaller than the distance to the next star Colour cameras and the ArtemisRGB utility Basically the Colour version of the Atik 16 cameras are the same as the monochrome coun terparts both in aspect and functionality However they feature a CCD which has colour filters built in enabling the capture of colour images in a single exposure Artemis Capture handles these cameras just like the monochrome versions but features a menu dedicated to colour imaging The Colour menu has 3 options RAW Displays the image as it comes from the came
8. ra Colour Displays a sinthetized colour image from the RAW data Luminance Displays the Luminance channel of the image grayscale Qeep in mind that all these options only affect the way the image is displayed Images are always saved as RAW data Since images are saved in RAW data there is a need to decode colour data for further processing Thats where the ArtemisRGB utility enters ArtemisRGB is a standalone application designed to work with FITs files produced from Artemis cameras fitted with colour CCD sensors The CCD sensors in these cameras have a matrix of colour filters over the sensor elements so each pixel samples a certain colour of the image The function of ArtemisRGB is to take this sampled image and convert it back into a full colour image Features Conversion of images from Primary RGB and Secondary CYMG mosaics Allowance for offsetting image on matrix Adjustable low pass filtering of colour Adjustable high pass filtering of luminance Adjustable image brightness Apply same conversion settings to a batch of images View raw image colour version or luminance greyscale only Output in various formats for post processing including FIT TIF BMP When you start ArtemisRGB you will see the main image preview area occupying most of the window On the left is a list which will contain the names of all the images to be processed Above this are some controls for specifying how the processing is per
9. s you can take a shot aa ad using the Camera Snapshot menu option or by clicking the camera toolbar button The indicator at the bottom right of the window shows the 8 h i gin 1 current camera status exposure time remaining download state etc sta stw fo Once the image is downloaded it will be displayed on the main screen width 0 Height 0 you can adjust the display using the Display Options dialog Fulltame Autosave Images _Erowse Note on the ATK 16 camera TEE If your camera is the ATK 16 model not the HR model the CCD sen 2 sor is of the interlaced type normally used in video cameras the Sony a ICX 429ALL Because of this an exposure with full vertical resolution The Exposure dialog box i e Y binning 1 has to be taken in two fields consisting of odd and even scan lines respectively These fields are then interleaved to produce the final image Due to the time taken to download a field the exposure times of the two fields may not match exactly in which case some fine horizontal banding may be visible in the image this effect is reduced at longer exposure times like 30s and over The effect is eliminated by stacking a few frames wich you will have to do anyway if using exposures under 60s For short expo sures less than about 2 4s the camera will take the two exposures consecutively rather than simultaneously only starting the second exposure after the firs
10. sing parameters for a batch of images Finally when you have set all your images as you like them you can use the Save All but Page 7 ton to convert all the images to a file format suitable for post processing You can choose to save as separate Red Green and Blue FITs files or a single 3 layer FITs file or a 48 bit uncompressed TIFF file or a 24 bit BMP file The last option will lose information but is more compact and more widely used than the other formats When using the first option each im age is saved under its original filename with R Gor _B appended to indicate the colour channel Other controls There are a few other controls apart from the dialogs described above The most important are probably the Camera Snapshot and Camera Loop menu options also available as the two toolbar buttons the loop button is the one with the red circular arrow on it The Snapshot command takes a single image and the Loop command starts the program tak ing repeated images You can abort the current exposure by clicking the Snapshot button while the exposure is in progress If you want to terminate the exposure early but keep the result hold the shift key down while you click the Snapshot button When looping you can stop the whole looping process by clicking the Loop button again The current exposure will be aborted You can change exposure settings while looping but they will not be acted upon until the start of th
11. t field has been downloaded In addition with this type of CCD it is physically impossible to produce true vertical binning at any odd multiple apart from 1 The Artemis driver will simulate the correct binning behavior if such a binning multiple is requested To atenuate this effect a Debanding filter is available in the Exposure dialog box which will cancel out most of it The Display Options dialog This dialog is displayed using the View Display Options menu item or by clicking the tool bar button It allows you to adjust the way in which the 16 bit image is mapped to the PC s display In general two values are chosen within the range of 16 bit numbers present in the image Pixel values equal to or less than the lower value are displayed as black and pixel values equal to or greater then the higher value are displayed as white Values in between are dis played as shades of grey The Log value controls how the grey shades are distributed a value of zero produces a linear map negative values provide higher contrast at the higher end and positive values boost the contrast at the lower end The Auto stretch box allows the program to automatically adjust the black and white levels each time an image is captured The levels are chosen such that only a few pixels fall outside the range If the box is unchecked then you can manually adjust the black and white levels using the sliders The Reticle check
12. then it is indicated by a red outline rectangle within the green one You can scroll the display using the scrollbars or by dragging it with the left mouse button Dragging the right mouse button within the CCD area allows you to set the sub frame interactively If you have a mouse with a wheel you can use the wheel to zoom Sub Frame Selection in and out the point beneath the mouse pointer is the focus of the zoom and remains in the same place on the display The Exposure Settings dialog This dialog is displayed by selecting the View Exposure Settings menu option or by clicking the toolbar button Here you are able to set the exposure time for the image the individual X and Y binning factors and you can numerically specify a sub frame if you wish There is a checkbox allowing you to specify whether the De banding filter is enabled This filter is useful for the Atk 16 camera as explained in the next pages of this manual Also a delay between exposures setting is available since it is desirable to have the autogu ider stabilize before starting the next exposure This can be set in the Dely s box and it s measured in seconds If the Autosave box is checked then every time an image is captured it will automatically be Page 3 saved as a FITs file with a sequence number appended to its name in k ap A the form C Artemis_001 fit Exp s D0 mn e H Once you have selected the exposure setting
13. tik 16 camera is not connected or powered up It is possible to run the program without the camera although most of the functions will be unavailable Page 2 The main settings in ArtemisCapture are controlled using two dialogs the display options dialog and the exposure settings dialog Both of these are modeless dialogs which means that they can be left open while you run the program and capture images etc However you should be aware that if one of these dialogs is selected then certain keyboard shortcuts or mouse operations in the main window may not behave as expected If this happens simply click on the main window to select it Quick Start lf you want to simply take a quick shot to verify that the program and camera are working correctly you can use the F1 F8 buttons to take a single test image F1 F4 take an exposure of 0 1 1 5 or 10 seconds respectively and F5 F8 use the same exposure times but binned at 2x2 for greater sensitivity Here s a list of shotcuts F14 0 1s amera Colour Kenma Help F2 15 i ia F3 5s Se F3 F4 10s 10s F4 F5 0 1s binned x Q 1s FS F6 1s binned F7 5s binned pate Fe F8 10s binned The Quick menu The Main Screen The main window in Artemis capture is used for displaying the most fi recently captured image A green outline rectangle is displayed in the window indicating the full size of the CCD sensor If a sub pmm frame is being used for imaging
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