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AP7P and AP8P Fix for Horizontal Bleeding of Bright Stars

Mode=0 Mode=2
General
Aside from the normal vertical "blooming" caused when bright points of light saturate the pixels of a CCD, earlier versions of AP7P and AP8P cameras also suffered from horizontal bleeding of bright points. The above images show the effect. The brightest star, at lower right, shows the most significant bleed, spanning nearly the entire height of the vertical bloom above and below the star. The image at right was taken after changing the "mode=" parameter of the initialization file and then reinitializing the camera.

The CCD manufacturer, Scientific Imaging Technologies, Inc. (or "SITe"), has recommended a solution for AP7P and AP8P owners that eliminates the effect, as illustrated in the above image examples. The solution is to operate the CCD in MPP mode, except during readout. During readout, a partial MPP mode is used to help negate the effects of a design issue with these CCDs.

Operation
An INI file change is all that is necessary to activate each mode. To change modes, edit your camera's INI file (e.g., AP7P.INI) and change the "mode=" parameter value. The default value is "mode=2". This setting will prevent horizontal bleeding of bright stellar-shaped features in your images. Use "mode=0" (zero) to operate the camera without horizontal bleeding prevention. Save the changes, exit Notepad, then reinitialize the camera from within the control software.

Notes:
Cameras with firmware earlier than P3 need a PROM update in order to use the mode=2 setting in the INI file. If in doubt, the firmware in your camera is indicated on the Test Data report that came with it. Contact Apogee to receive the firmware update. Your camera should have P3 if it was shipped after July 1, 2000.

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