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Post by steveg on May 21, 2011 0:44:41 GMT -5
I need advice on the lens Istar offers. I was looking at two of the 5" f8 lens. I would like f10 but I think f8 I can make it work. If they can make them f10 what is the normal lead time? Do they charge extra? How close are the lens in focal length? The goal is to finish it before Aug. and it is 75% is done. This maybe unrealistic to build it by then. Here are some pictures. I was going to use 6" mirrors but now decided to use 5" lens. the picture has 8" tubes but I have 7" tubes new and they will mount fine. webpages.charter.net/kb4mxo/binofixure.jpg webpages.charter.net/kb4mxo/binoprism.jpg webpages.charter.net/kb4mxo/binopart2.jpgwebpages.charter.net/kb4mxo/binosled.jpgHas anyone built binos with the lens? I am ready to take the leap and order but need more input . They say the Istar stuff gives good views. I think this should make a killer set of binos. Thanks Steve |
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Post by Watcher3 on May 21, 2011 4:32:55 GMT -5
Welcome aboard Steve!
Unless they are already working on an F/10, I think it would be cost prohibitive for a custom lens. I believe the design and tooling fees basically add up to a bit more than the cost of a 5" lens. I would shoot Ales an email, He's very helpful, and you can discuss all your options to find a good solution.
I think MR. Bill over a CN was planning on 6" F/5 ISTAR lenses in a binocular, but I don't know if he ever got started yet.
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Post by steveg on May 21, 2011 6:03:56 GMT -5
This sounds like a great group of people and I hope my project will help others.
Istar offers a R30 F12 for about 100 bucks more,but for a proof of concept scope the price is starting to get high. If I go a bit more I could go to 6", but you have to draw the line some place. The prism train diameter is the main issue here and fitting the light cone in it. Here is some notes on calculations I made for a 6"f8.2 mirror and the Russian surplus optics:
webpages.charter.net/kb4mxo/prismtrain.jpg
webpages.charter.net/kb4mxo/binocalc1.jpg
webpages.charter.net/kb4mxo/prismax.jpg
Thanks
Steve
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Post by Watcher3 on May 21, 2011 9:40:09 GMT -5
Don't get me wrong. I don't want to point anyone away from ISTAR, but for a "proof of concept", you would do well to get on the Surplus Shed list for their 127/1200 lenses. They come into stock sporadically, but you never know. It could be a long wait, or a short one. Not top quality optics, in a plastic cell, but pretty good performers from what I hear.
Whatever lens you end up with, it's great to have you and your talents and knowledge here. Please keep us up to date with this project.
Joe
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Post by steveg on May 21, 2011 10:35:26 GMT -5
I looked at the SS optics and had a Meade 5" f8 if I can remember and it had Ok views. The SS optics could better than Meade ones but that issue coupled with waiting forever to get them, I decided to go for a known high quality lens. Istar has a 2 month turn around?
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