Thanks to: "Robert E. Kruse (kruse@vnet.ibm.com)" How to Make a Zuiko Lens into a Telescope I decided against the Kenko spotting scope converter since it uses a simple 3 element eyepiece and an erecting roof prism. To be done well, far more than $80 needs to be spent on those items. Plus, it can't be used for anything else. I opted to buy a high quality 1 1/4 inch astronomical eyepiece and adapt it to work on the back of any Olympus lens. The view is upside-down, but that doesn't bother me as much as a blurry image. Here is a description of how I converted any Olympus mount lens into a spotting scope. I started by purchasing a used Olympus 25mm manual extension tube from B&H Photo for $10 (as part of a larger order). It has an outside diameter of just less than 2 inches. The rest of the adapter parts cost less then $3 at any home improvement store (a 2 inch to 1 1/2 inch PVC taper fitting, 3 x 1/2 inch long thumb screws, and 3 x 3/4 inch long thumb screws). The whole thing can be made for under $15 and 30 minutes of work (not including the eyepiece or shipping charges) with a drill (a variable speed power drill helps). Since there are no optics in an extension tube, the eyepiece must be mounted very close to the back of lens. On the other hand, the eyepiece can project quite far into the inside of the extension tube because there are no optics. I used a 2 inch to 1 1/2 inch PVC pipe adapter that tapers from one size to the other. I drilled three holes evenly around the 2 inch end quite close to the very end to allow for it to be moved back and forth along the extension tube for rough focusing later. I then put a thumb screw in each with rigid plastic taped on the inside to protect the outside of the extension tube. When tightened, the three screws really hold the adapter tightly onto the tube without losing optical alignment. In the 1 1/2 inch end, I drilled three holes about 4mm back from the edge of the taper (this was discovered through trial and error). I then put the longer thumb screws in each with no protection on the ends. The eyepiece is then centered in the 1 1/2 inch end and the three thumb screws are tightened around it. This holds the eyepiece very securely in place. It receives only minor scratching. Next I put the whole assembly on a lens and set the lens for infinity focus and moved the 2 inch end back and forth on the extension tube until focus was achieved. I then carefully tighten the screws. Now it is parfocal with all Olympus lenses and zooms remain zooms and not varifocals. This makes for a secure mounting that can be quickly removed from the telephoto lens just like a camera body. The entire setup is very sturdy due to the set screws everywhere. Plus, the aperture ring controls the diaphragm since the extension tube forces it to be stopped down continuously. The eyepiece can be any 1 1/4 inch astronomical eyepiece. You could adapt this design to work with other sizes, I suppose. I bought a 9mm Vixen Lanthanum LV eyepiece at the suggestion of Michael Covington and due to its multicoating, long (20mm) eye relief, and it roughly creates a 10x magnifying effect on the lens (500mm / 9mm = 55.6 power). It's very sharp with its 7 elements. I paid about $115 plus shipping for this eyepiece from Adorama. It can also be used in almost any telescope. Any high quality eyepiece such as this will easily show the limits of your lens. I tried it out on my 50mm f1.4 Zuiko and found that the image of the moon bleeds severely in the extreme red and blue at f1.4 and less so f2.0. Only at f2.8 and above does it produce a nice round white moon with no color fringing at all points in the image circle. I use a Bogen 3221 tripod with a 3130 fluid head to smoothly pan around the sky. I use a 500mm off brand lens with the converter. The lens needs a tripod mount on it for this to work. I handhold others for rough evaluation of optics. Bright objects such as the moon, Jupiter and its moons, comet Hale-Bopp, and the Orion nebula are easily seen. I can even pick out the trapezium stars within the latter. Bright objects such as the moon appear better stopped down a few stops. Lunar craters are easily picked out at first and last quarter. I can put any Olympus mount teleconverter on it that I want as well. I will admit that 50 power is about the usable limit on most objects with a 500mm lens. However, the moon can be pushed much further with teleconverters since I can stop the lens down and vastly improve clarity. I've done this during the day to read house numbers from over 500 feet away. Overall, I like the setup enough to want to get a "real" telescope now. The moon is especially neat to look at. I just want more light gathering ability now for dimmer objects and to reach higher magnification levels for planets. Bob Kruse