Thread subject: :: Stereo Microscope

Posted by ChrisR on 07-12-2007 09:46

You are correct - a disecting microscope is absolutely essential for the serious study of Diptera... unless you have amazing eyes! ;) I make the distinction between "disecting" and "stage" microscopes because with stage microscopes are used mainly with glass-slide preparations and we usually work with large, hand-held subjects. Having a stage microscope might be useful if you want to examine really tiny fly genitalia (or Collembola or chalcids etc) and make slide preparations of them for long-term storage. But most fly genitalia are too big to be mounted under glass and they often need to be viewed from the side.

I use a Meiji zoom stereo disecting microscope with 7x - 45x magnification, which I find perfectly adequate for tachinids. But for regular work with very small <3mm specimens you would need more magnification I think. Having a binocular microscope might be better than a monocular one (even if your eyesight is bad in one eye) because the kind of microscope you need is most common in binocular form - so you have more choice. But also remember you might take your microscope to a workshop or want to show a specimen to someone else, who would appreciate the extra comfort and clarity that binocular microscopes give you.

Good quality lenses are very important of course but I think lighting is at least equally important so I would always recommend a strong, white light such as a fluorescent tube (or diode) lighting system. They can be simple table lamps but it must be possible to get the light close to the subject without obstructing your work. Having the ability to shine the light from different angles can also be useful for seeing dusting or fine hairs and surface structures.

I don't use a camera with my microscope very often and when I do I just hold my little Nikon Coolpix against one of the eye-pieces. It works quite well because the lens glass is close to the end of the lens-tube but on some cameras (like my Canon G7) it is protected by a metal ring, which causes too much vignetting. Anyway, with the Coolpix they are OK but you might like to buy a 'trinocular head' with a digital camera attachment to take photographs directly down through the microscope's optics. This is a more expensive solution but the results are generally better and it is easier to make composite (layered) photos.

A spare eye-piece fitted with a graticule is also a nice, cheap addition to the equipment. A graticule is a device for projecting grid or graduated lines onto the image so that you can measure the relative size of parts. With tachinids we often have to measure the relative width of the eye/frons and with ichneumonids the relative length of the ovipositor/hind-tibia is very important. Without a "ruler" or some form of in-image measuring it would be almost impossible to get the necessary accuracy.

Hope that helps :)