Last updated: 27 May 2004
Subject: Very easy Hartmann mask for ETX-105 Sent: Wednesday, May 26, 2004 15:10:04 From: Leo Bodnar (firstname.lastname@example.org) I found quite a good source for Hartmann masks for ETX-105. They are covers for those CD-R sold on spindles in 10, 25, 50 quantities without jewel cases. I had a few and some of them fit tightly some a bit loose - choose to your taste. 1. Cut the holes with exacto knife. Plastic is a bit brittle so work your way slowly from both sides. 2. Spray some paint on the outside to make sure that even if it ever flakes off it's going to be on the outside from the front lens. Or use sticky tape. Should not necessarily be 100% optical black! 3. I have cut off three of those little tabs that lock the cover when twisting it on the base. Don't! Leave one on and use it as a flag to indicate "up" position for the Mask - works even in darkness! That way you are going to be consistent with image orientation with relation to focussing in/out. 4. Keep another CD-R "cake" cover as a quick scope front element protector. Much lighter, cheaper and easier to find when dropped in the field. Use original one when transporting. Plastic one fits on top of metal one when not needed. Best wishes Leo Bodnar
Mike here: For more on the usefulness of the Hartmann Mask see the article '"Hartmann Mask" Focusing Aid'.
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