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I have been watching these comments on this thread for a while and thought this might be of help.
It if is determined that it is necessary to confirm a perpendicularity between the objective and stage, here is a simple test you can do.
Remove the condenser, close down the field diaphragm, use a monocular tube if you have one (best option) place a centered pinhole aperture in place of the eyepiece.
Do not use a crosshair eyepiece.  Use two 50% windows, place one on the stage within the image path and hold the other one to the nosepiece opening where you screw in the objective, now looking through the pinhole you can "buglight" the reflections of the light coming from the center of the field diaphragm.  If the shoulder of the objective mount is parallel with the stage surface they should line up perfectly.  If your scope has a fixed tube-lens within the path, this might not work but it is worth a try.  Otherwise you might need to contact your service provider and ask them is the have a stage square.  A stage square is a device that screws into the nosepiece in place of the objective and has a parallel 75mm diameter ± reference plane that makes contact with the stage.  By slowly focusing upward until the stage square just touches the stage you can see if it touches equally all around or if the stage or nosepiece is tilted.   

Dan


On Apr 23, 2015, at 8:04 AM, Lathrop, Kira L wrote:

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Dear Christophe,
When I started here I was testing PSFs on one of the scopes and was getting dramatic asymmetry in several objectives. After much hunting and testing it turned out that the objective turret was cross-threaded. You might just try unscrewing your whole objective turret and reseating it. 
Best of luck,
Kira

Kira L. Lathrop, MAMS
Assistant Professor
Co-Director, OVSRC Imaging Module
University of Pittsburgh
School of Medicine, Department of Ophthalmology 
Swanson School of Engineering, Department of Bioengineering
203 Lothrop Street Room 1032
Pittsburgh, PA 15261
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Dan Focht
Bioptechs, Inc.
3560 Beck Rd.
Butler, PA 16002
www.bioptechs.com
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