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I have a question regarding our inverted-phi axis-mounted video camera, used to centre crystals in the path of the x-ray beam. If I centre the crosshairs on a crystal so that it stays perfectly in the middle with no precession - no problem, the beam hits and you get diffraction. Thereafter, if I zoom in or out, the crosshairs will no longer centre perfectly on the original part of the crystal, but will be significantly off to the left or right hand sides, with the result that centring on crosshairs means you'll miss the crystal with the beam. I realize that this is because the video camera is not fully aligned (as, say, the detector has to be aligned within a couple of pixels all the forward and all the way back) and is designed to be in-focus at a specific distance, matching the distance from the camera to the crystal in the beam. My question is this: when using very small crystals, is there a simple way to get your video camera to zoom in to check if the crystal is actually in the x-ray beam. We use a Rigaku M007 HF and r-axis iV++ detector. Hope this makes sense! Best regards Mark _____________________________________ Dr Mark Agacan Scientific Officer, Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, Dow St., University of Dundee, Dundee, DD1 5EH Tel: +44 1382 348751 Fax: +44 1382 345764 _____________________________________
