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  1. #3
    Join Date
    Oct 2005
    Mesa, AZ


    UPDATE 17-Jan-2018: The ASCOM Initiative has provided a tool for making the security change to EXE drivers, elimininating the need to do the procedure below for EXE ASCOM drivers. You may still need to make this change to programs that have Programming Interfaces used by other programs, so we're leaving the manual instructions below. The tool is located at

    To use it:

    1. Create a new directory on your PC
    2. Extract the three files in the zip into the new folder
    3. Double-click the FixDCOM executable (you may need to answer yes run after downloading)
    4. Answer Yes to the "Do you wish to allow changes?" security dialog
    5. Select the "Apply revised settings..." from the dropdown list
    6. Click Apply

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    MANUAL WORKAROUND: As the Microsoft supplied workaround in the previous post says, the components need to have their call level changed to "Call". Thank goodness, this can be done using the DCOMCNFG tool, an MMC snap in. The tricky part is going to be identifying the various ASCOM and application servers you need to adjust!! Read all the way to the end or you'll miss important and useful stuff.

    Don't do anything unless you actually have a problem.
    Note that neither ASCOM nor its client apps use Distributed COM (DCOM). The names are historical only.

    1. Type DCOMCNFG into the Windows Search box (lower left corner of your screen). You may have to wait a while while it installs the Component Services snap-in the first time you do this. Be patient.

    2. Eventually you should see the Component Services window. Expand the tree to see DCOM Config

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    3. Now for the tricky part. Under the DCOM Config "folder" is a long list of components, most of which belong to Windows itself and to the many apps that make use of this Windows feature (COM). Your task is to locate those which you need for your astronomy uses. This will include drivers for devices and anything that may be used by another app. POTH is an example, it is used by other programs because it looks like a telescope, dome, and focuser to its clients. If in doubt just change its authentication level, it's harmless. Use the ASCOM Profile Explorer to find the System name for the devices you see in the Chooser. Then find it by system name in DCOMCNFG. Here is the entry for the "Telescope Simulator for .NET" in the ASCOM Profile Explorer

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    Note that it's system name is ASCOM.Simulator.Telescope.

    4. Now find this in DCOMCNFG's list of components. Right click, Properties, then change None to Call in Authentication Level. Then click OK:

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    5. If you don't find your problematic component in Step 4, then run a 32-bit DCOMCNFG.
    5a. Open a CMD shell enter CMD into the search box)
    5b. Type C:\WINDOWS\SYSWOW64\mmc comexp.msc /32
    5c. Now look in this DCOMCNFG for your troublesome component (MaxIm DL will appear only here for example!)

    Continue finding things in the ASCOM Profile Explorer and the 64-bit and 32-bit DCOMCONFG, setting the Authentication level to Call. If you encounter a non-ASCOM component that stopped working after KB4075892, and you know it has a scripting or programming API then find it in DCOMCNFG and change its Authentication Level to Call as well. This includes ACP itself which is listed ACP Observatory Control Software.

    * For Software Bisque TheSky X look for TheSkyX and TheSkyXAdaptor and change both to Call
    * For MaxIm DL you must look in the 32-bit DCOMCNFG and you'll find it as MaxIm.CCDCamera
    Last edited by Bob Denny; Jan 18, 2018 at 18:07. Reason: Add 32-bit DCOMCNFG info as well as MaxIm and TheSky identifiers
    -- Bob



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