Last updated: 15 October 2002
Subject: Prime Focus With Filters Sent: Friday, October 11, 2002 16:10:27 From: firstname.lastname@example.org (Adrian Vergot) I couldn't find a solution on your site for this problem, so I came up with my own and decided to share it in the hopes that others might benefit. Thought this might be a good entry to the "Astrophotography:Some Technical Tips:Prime Focus With Filters" Prime Focus With Filters I currently use my ETX70 for prime focus wide field photography, and wanted to use my nebular filter. I have a collection of 1.25" filters, but I discovered that the internal thread on the ETX rear camera port was too large (though close). I was going to start looking for a step-down adapter, but came up with the following solution using good old "Fun-Tack" (though I think now adays they call it "sticky-tack"). It creates a rock solid temporary bond between the filter and the scope without marring the metal, and which can easily be removed with a simple twist of the filter. Here is what I did. Select your filter, and wad up a small ball of fun-tack as shown.
Next, roll the ball into a rope about the size of the circumference of the filter. On the threading of the filter, snugly wrap the rope around it. Push the fun-tack slightly inward so that it sinks into the threads. Next, push the filter firmly into the back of the ETX rear port housing. Excess fun-tack will bulge out from the edges. Using your fingernail or small plastic spatula, trim off the excess fun-tack. Finally, Attach your T-Ring and camera, and you are ready to go!
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