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rsweatt
Joined: 07 Feb 2013 Posts: 43 Location: Virginia
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Posted: Sat Aug 23, 2014 1:53 pm Post subject: |
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Well, I purchased an 8X10 sheet of what was claimed to be 1st surface acrylic mirror but it can be used either way, 1st or 2nd surface. It is 1/8" and was a bear to cut to size without doing any (much) damage to it. I did get a piece cut and installed but since the brackets that hold the OIM mirror are designed for a 1/16" mirror it was difficult getting the bolts to catch in the brackets - but the main drawback of using acrylic mirror seems to be that if you get the bracket bolts good and snug the mirror flexes to the point of distorting the reflected image, so I had to back the bolts out a tad. I am beginning to think I will try taking Parkeralto's advise and just give 2nd surface glass mirror a try, as 1st surface may not be completely necessary. I am going to see if my local glass company can cut a piece to size. |
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EdSawyer
Joined: 19 Sep 2013 Posts: 3
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Posted: Fri Sep 05, 2014 1:33 pm Post subject: Edmund Optics |
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Edmund Optics is one source for custom-cut, first-surface mirrors with various materials (aluminum, silver, gold, etc.) May not be the cheapest solution but I would expect it would be at least as high quality as any other source, and perhaps moreso than most. |
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Jim C.
Joined: 18 Feb 2011 Posts: 89
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Posted: Fri Sep 05, 2014 1:57 pm Post subject: |
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EdSawyer wrote: | Edmund Optics is one source for custom-cut, first-surface mirrors with various materials (aluminum, silver, gold, etc.) May not be the cheapest solution but I would expect it would be at least as high quality as any other source, and perhaps moreso than most. |
I have purchased first surface mirrors on the 'Bay for my RB projects
amateur telescope makers use them, and they do come up from time to time.
Last 8x10 sheet I bought was about $35. |
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rsweatt
Joined: 07 Feb 2013 Posts: 43 Location: Virginia
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Posted: Sat Sep 06, 2014 3:48 pm Post subject: |
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Well, the Acrylic was a bust - it was pretty much impossible to get accurate focus as the mirror just is not flat. Fine for smaller apertures but for shooting wide open, the reflected image was a tad wavy. Put the original mirror in and will just put up with the slightly dimness until I can get exactly what I want - 1/16th" front surface. |
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Brandonium
Joined: 30 Mar 2016 Posts: 6 Location: Helena, AL
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Posted: Tue May 24, 2016 11:59 pm Post subject: Re: Graflex SLR Mirror |
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I know this is an old post but I'm not 100% on if my new mirror will require shimming of the ground glass. The old mirror and new mirror both measure 1.9mm in thickness. On my compact the mirror that I replaced was a second surface mirror and I replaced it with another second surface mirror however my 4x5 graflex auto now has a first surface mirror. Are we saying that the difference between the substrate on a first and second surface mirror is 1/16" or 1.5mm?
Parkeralto wrote: | I can add a bit of my experience to that very competent answer. Because the image is large format, it does not require high quality mirror; in fact the thinnest cheapest stuff you can find works great because it is light weight. I have replaced a few Graflex SLR mirrors with first surface mirrors; available from kaleidoscope supplies. There is a problem with focus that will require shimming the ground glass. Even a thin first surface mirror puts the reflective plane 1/16" closer. It is a little fussy but not difficult. The pay off is a brighter sharper image on the ground glass; not a dramatic difference from a new, regular mirror but for me quite noticeable and worth the effort. |
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