The Celestron 44302-B Digital Microscope

Description and features

The Celestron 44302-B is a low-cost (under 50 dollars) digital miscroscope:

• 2 MP digital camera (640 x 480 color images).
• Ring illuminator with six white LEDs.
• USB interface.
• Chrome-plated metal stand.
• Chrome-plated metal base and articulated support arm (with 2 ball joints).
• Plastic body and hoding clip.
• Continuous 1:4 zoom
• Software-interpreted trigger button (top).

The articulated arm allows the microscope to be positioned upright at various distances above the specimen. A single thumb screw tightens both ball joints of the arm. To change the magnification, one must raise or lower the microscope and adjust the focus accordingly. The focus knob is a light gray plastic tube section with low ridges that is partially exposed through a window on the side of the tube.

Resolution

The labels "<-10X" and "150X->" are printed on the body just below the focus knob, but ofcourse they are rather meaningless for a digital imager. Actually, the camera focus all the way from infinity (when the knob it turned all the way in the "10X" direction) to less than 1 cm (when it is turned the other way).

When the arm is fully vertical, the microscope's transparent skirt lies 34 mm above the tabletop. At that distance, the field of view on the tabletop is 18 mm wide, so that the resolution is about 35 pixels/mm (90 pixels/in).

When the skirt sits on the tabletop, the field of view on the same is ~2.2 mm wide, so the resolution is about 290 pixels/mm (740 pixels/in). The range of magnifications (with the tube on the stand and the specimen flat on the tabletop) is therefore about 1:8

That is not the maximum magnification however, the microscope can focus on objects that are slightly inside the skirt. ??? , so the resolution is about 290 pixels/mm (740 pixels/in). The range of magnifications (with the tube on the stand and the specimen flat on the tabletop) is therefore about 1:8

At all magnifications, the dept of focus is very small. At maximum magnification, a vertical displacement of the specimen by ~0.1 mm causes visible blurring:

Image quality

The images are sharp when properly focused, but

The manufacturer provides only Windows and Mac software in the box. However images can be captured on a Linux PC by the XSane scanner utility or several other programs, and saved as 640 x 480 pixels, 24-bit color. The trigger button at the top of the microscope seems to be ignored by Xsane.

The arm is to short, and at maximum height

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Last edited on 2014-01-14 00:53:57 by stolfi