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post #1 of 6 Old 10-12-2007, 10:18 AM - Thread Starter
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Hi all,

I have been posting previously in the dedicated room forum and ventured on here last night since I am doing a scope setup in my new HT. I will be using a CH setup and had considered making my own lens using wedges if crystal as mentioned in several posts. Considering after market lenses are so expensive I would prefer to make my own.

I am however confused as to how to determine what angles to set the prisms at. How is that determined? Trial and error? I am pretty handy and could probably find the prisms at a decent price as long as I am not wasting my money by not being able to figure out the angles required.

Any comments or help on this is appreciated.

John
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post #2 of 6 Old 10-12-2007, 06:11 PM
 
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John, the angles are critical.

Also the prisms you will need are quite large (at least 4 inches square, preferably larger to accommodate wide projection beams). This means they will be bigger than any available over the counter, or even on commercial order from most specialty optics houses.
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post #3 of 6 Old 10-12-2007, 06:50 PM
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This whole sub forum is about DIY lenses, screens etc, so plenty to read...

Mark

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I love my Constant Image Height system!
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post #4 of 6 Old 10-12-2007, 07:42 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

This whole sub forum is about DIY lenses, screens etc, so plenty to read...

Mark

Mark,

I have been reading a lot about them, bothh on this site and your blog. I think I got it down. It seems that basically you set up the prisms as shown in multiple threads. Adjusting the rear prism sets the left edge, the front adjusts the right. Both prisms must be plumb for it to work well. The longet the throw the less chance for pin cushion and other distortion. The closer you can get the lense the less CA you will have. Just winging it here. Lots of other small factors can come into play but that seems to be the basic jist of it.

I may just go to the local crystal engraver around me and see if they carry crystal wedges. Or maybe just order the wedges from Massilon or somewhere else. I have thought about the Aussiemorphic and sent and e-mail about it and am awaiting an e-mail back. I keep hearing about it being a great lens for the price but I have yet to find a price If you know how much they are you can PM me.

Otherwise I will wait for an e-mail back from Oz.

Thanks for the reply.

John
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post #5 of 6 Old 10-12-2007, 10:01 PM
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Quote:
Originally Posted by John Martin View Post

Adjusting the rear prism sets the left edge, the front adjusts the right.

Hi John,

Close, it is actually the rear that controls the right hand side...

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Both prisms must be plumb for it to work well.

Very true. if the prisms are not vertical, your image will skew...

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The longet the throw the less chance for pin cushion and other distortion.

Yes longer throws are way better than short...

Quote:


The closer you can get the lense the less CA you will have.

To correct CA actually requires two different glass types which is one reason the pro lenses cost what they do...

Mark

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post #6 of 6 Old 10-13-2007, 06:01 AM - Thread Starter
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Mark,

I got the e-mail. Thanks.

John
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