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Message: <blockquote data-quote="Surveyor" data-source="post: 1281758" data-attributes="member: 50720">Ronh; I guess I should explain some points that I use that influenced my assumptions. In the lab, a lot of times it is easier on the math to use multiples of the focal length to keep the math simple to double check the results in my head instead of waiting to the end of a test and then figuring out something was set wrong. 168 x 10=1680. In my attachments of the tables I showed, I just showed the normal distance calculations. I have a page for my collimator calculations. You can put the bar target in a collimator and adjust the math for whatever ratio you wish, place the collimator lens right up against the objective under test, and the bino will focus at infinity. This way you are making the measurements at the design infinity setting even though the target may only be 100 or 200 mm from the objective. I have attached a picture of my USAF target in the collimator, 400 mm from the camera lens focused at infinity. Group 5, element 3 is 40 lp/mm. Now the harder one. I have attached the second page of my resolution sheet. My primary collimator for resolution work has a 400 mm focal length. If for some reason I want to change to a 1680 mm focal length, I really do not have to change anything. At the end of the sample run, all I have to do is adjust the reading by a factor arrived at using the desired focal length divided by the collimator focal length and just correcting by that factor; 1680/400=4.2, I pick a group, element that has 168 lp/mm. (4.2*40). Or, if like me, you have a decent lens kit around, you just take a 0.6 diopter lens and a lens holder and target holder and set up a test set that would have a 1667 mm length, within 1% of 1680. There are many ways to get to the desired results while staying on the tabletop. Hope I have my numbers correct in this quick run down.Best.Ron Sorry Ronh, I just noticed that in my haste here at the office that I have an error in the spread sheet. The distance information in the first column for distance should read 1.68 instead of .168 and the values for Arcseconds/LP need to be divided by 10 and match the lower set. Now you see why I have to keep it simple. Also, I was just going on your assumption of the 168 mm focal length and 10 times 40 lp/mm=400 seemed resonable as a quick guess for a 42 mm objective. All done by guessing, not by trying to make the numbers fit anything in particular since it was all assumed anyway.</blockquote>

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