Orion 52080 instruction manual Color Balance, Stretch

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Figure 14. The Filter functions can help bring out subtle detail in an image.

Figure 15. The Color Balance command allows weighting of each color plane to improve the overall color appearance of an image.

Color Balance

The sensitivity of most CCD cameras as a function of wavelength (color) is dif- ferent from the response of the human eye. The filters used for creating color composites also have their own characteristics, as do the telescope optics. Although “perfect” color rendition is an elusive if not impossible goal (all indi- viduals see colors slightly differently), it is straightforward to get “good” color

balance with simple weightings. This is where the Color Balance command (in the Process menu, Figure 15) comes in handy to touch up the resultant colors in your images. Use the Preview Image to see how altering these parameters will affect your image (or click the Full Screen button to see the changes applied to your full image).

Color images from CCD cameras typically require a background level adjust- ment. This is accomplished by bringing the background level (or bias) in each color plane down to zero. Each of the Background Level values is subtracted from every image pixel in its color plane. Any pixel values that become nega- tive are forced to zero. The Auto button automatically determines the settings necessary to equalize the image background in all three color planes. The Reset button resets the background level subtraction to zero on all planes.

Scaling adjustment (entered as a percentage) allows you to compensate for transmittance differences between the filters used to acquire the three color planes. Values of 100% result in no change. The scaling percentages can be typed in or adjusted using the “spin” controls (small up and down click arrows to the right of the scaling numbers). The Preview Image is particularly helpful in monitoring the results when using the spin controls. The Reset Scaling but- ton resets to 100% on all three planes.

The Click On White Area to Set Scaling check box enables the operation of the mouse to set the scaling. Set the Background Level first (you can use Auto), then click on a white object (e.g. a neutral-colored star) in the image (not the Preview Image) with the mouse. The Scaling settings will automatically be adjusted to make the selected point appear white. If an area of the image is known to be white (or gray), this is an easier way to determine the scaling factors, and can be used to instantly color balance the image.

Stretch

The Stretch command (located in the Process menu, Figure 16) modifies the brightness and contrast, and optionally the range (maximum and minimum pixel values) of an image. Unlike the screen stretch settings in the Screen Stretch Window, which only affects the how an image appears on the com- puter screen, the Stretch command actually changes the image data pixel values in the memory buffer. In reference to the histogram, the Screen Stretch Window changes how the histogram is displayed on the computer screen, the Stretch command alters the histogram itself.

There are three elements which must be set: the Permanent Stretch Type, the Input Range, and the Output Range. You can use the Preview Image to see how changing these parameters will affect the resultant image (or click the Full Screen button to see the changes applied to your actual image). You can also open the Screen Stretch Window to see how changing these parameters change the histogram.

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Contents Orion StarShoot Deep Space Color Imager System Requirements refer to Figure Parts ListTelescope Mount Power and the TECComputer Software Installation Software and Driver InstallationCamera Driver Installation To install the camera driver on a Windows XP computerSelect Locate and install driver software recommended To install the camera driver on Windows Vista computerObtaining First Images Getting Started During DaylightScreen Stretch Window Stop button in the Camera Control WindowImaging the Moon Astronomical ImagingImaging Planets Imaging Deep Sky Objects Dark Frames Camera Control Window, set the Mode to Dark Raw Light and Dark Mono 2x2 Modes Image ProcessingMake Pixels Square FilterStretch Color BalanceRecommended Processing Sequence Batch Process Using The SSDSI-II As An AutoguiderClick OK in the Ascom Telescope Chooser window Computer to Mount ConnectionAutoguider Calibration Camera Control Window, click on the Guide tabUse of Two SSDSI-II Other Features Of Maxim DL EssentialsEdit Menu View MenuWindow Menu TipsHelp Menu Polar AlignmentCamera Control Window, select Light Raw 1x1 mode FocusingUsing Focal Reducers and Barlow Lenses Turn off Dark SubtractSpecifications USB Extension Cable Care and MaintenanceOne-Year Limited Warranty