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Primary baffle tube, installing spiders squarely

Started by macdonjh, 09/09/2014 12:35PM
Posted 09/09/2014 12:35PM Opening Post
I have two questions for the knowledgeable people here:

1: What is the best way to determine the proper length of the primary baffle tube for a Cassegrain telescope? I don't have any design software, so I hope there is a geometric or analytic solution that can be done with a piece of paper, pencil and calculator.

2: What is the best way to locate four points on the circumference of a circle that are 90 degrees apart? I tried one method that didn't work well when installing the spider in my scope. Note that I do not have a machine shop, I'll be working with basic hand tools.
Posted 09/09/2014 04:54PM #1
1. Full scale drawing with ray traces drawn out. Then make measurements.

2. Wrap the tube with newspaper taped together to get a full circumference cover. Mark the paper at one point, i.e., the top. Remove the paper and measure the circumference and measure/mark the 1/4 distance points. Return to the tube and transfer measured points to the tube. Drill holes.