Last updated: 14 December 2003
Subject: Another inexpensive focus aid for ETX 125 Sent: Thursday, December 11, 2003 05:35:20 From: email@example.com (John(Jack) Fox) Here is a quick, easy and cheap way to make a Quick Focus Aid for the ETX - 125. It also makes a good lens cover. BTW, I wrote back a few weeks ago about having to send back 2 ETX 125's because they were defective. I finally got the 3rd one last week and it seems to be a winner this time. I guess the 3rd times the charm. Jack
Another Inexpensive Focus Aid for ETX-125
I found that a Cool Whip lid fits the ETX-125 OTA perfectly. In fact, you can use it as a travel lens cover and not have to fool with screwing and unscrewing the heavy metal lens cover (figure 2) and you wont have to worry about dropping it or stripping the threads. However, I would still use the metal lens cover for long term storage.
First, draw a large circle 5 7/8 in diameter (figure 1). Next draw the 120 degree triangle in the center of the circle using the measurements on the drawing (13/16 up from center, 1 5/16 down from center and 1 right & left of center). The 3 small circles are each 1 in diameter. All measurements are from the centerline of the large circle.
Next, cut out the drawing and use it as a template over the inside of the Cool Whip lid to mark the centers of each of the circles (large & small). The Cool Whip lid as a small dimple in the exact center of the lid to help center the template.
I use the point of my compass to gently push through the templates large circle center line and with the tip of the compass still through the template, line it over the dimple of the Cool Whip lid and press to mark the center of the lid. Now without moving the template, mark the centers of the 3 small circles the same way as the large by using the sharp point of the compass to press through the templates center line of each small circle. You now have a pin hole marking where you will be cutting out the 3 small circles.
I use a quality drafting compass that has a changeable cutting blade to replace the graphite drawing point. Set the lid with the inside facing up on a piece if thick cardboard or block of wood. This way you wont cut your table and you have something for the blade to cut into through the lid. Set the compass to cut a 1 circle and place the sharp point of the compass into one of the small pin holes on the inside of Cool Whip lid. Now begin rotating the compass with an even pressure to cut into the plastic lid. Be patient, the may take a few minutes to cut through. Cut out the other 2 circles the same way. Use fine sand paper to smooth the inside edges of the holes. Wipe both sides of the lid with a damp sponge or cloth to remove all plastic dust.
Finally, if you want, you can spray paint the top of the lid only with black or ETX blue paint that is made for plastics (available at Lowes or Home Depot). This paint is not suppose to flake off. Do not paint the inside of the lid. You dont want to take a chance on getting any paint on the lens surface. It may not be necessary to paint it at all, just a personal preference. The only problem you may have is people asking if you have any strawberries to dip in the Cool Whip.
Figure 1 - Template
Figure 2 - Inside of lid
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