Which Mirror for a Binocular reflector mount ??

[Windshift]

I am looking to build a mirror mount for 20x80 or 25x100 binoculars.

Something like this one.
http://www.tricomachine.com/skywindow/index.html (http://www.tricomachine.com/skywindow/index.html)

My question is; how do I establish what quality of mirror will be needed for This level of magnification.
I do not know how to calculate if I would need 4 wave, 1 wave or 1/4 wave and there is a LARGE price difference.

I am hoping someone has used one of known mirror quality, for a known magnification.

Or even better is someone knows how to calculate this.

Many Thanks

[SkyWatch]

My 5c worth is that the worst part of the optical train dictates how good your view is going to be: and 1/4 wave is the only one of these that wont make your image worse. Anything less is a compromise: but if you are going to compromise I would suggest you don't go for 4 wave... I suspect it would be like looking at a reflection in a lake, or using your binos through a window!

- Dean

[Windshift]

Thanks Dean,

That was my first thought Dean but 2 points make me question myself.

1. It must be much more forgiving than a scope as it is only 25 x magnification.

2. If it was 1/4 or 1/2 wave the commercial ones would be a lot more expensive than $280 (mirror is at least 250mmx200mm)

Given the cost differences :eyepop: I am hoping someone has done it or knows how to calculate it. :shrug:

[dannat]

i would test on a piece of standard mirror first -just to make sure you like the view & can orient your bino properly

then uy whatever mirror grade you're comfortable with

[Satchmo]

Do you have a link to the glass source I could look at ? It really depends on the kind of error and how localised it is . 25X will certainly not require 1/4 wave quality nor would the average binocular be any where near this quality .

[Windshift]

Thanks
I haven't yet found a glass source as I dont know what I am asking for.
I am aware that Edmond Scientific sell some front surface mirrors but still searching for other sources. There are some on ebay but I need to know what questions to ask to ascertain if they are suitable.

many thanks

[SkyWatch]

Have you looked at this thread, and/or contacted its originator?
http://www.iceinspace.com.au/forum/showthread.php?t=51971&highlight=front+surface+mirror

- Dean

[Windshift]

Hi Dean,

I tried the mirror source that he quotes but it seems that they have gone out of business :(

I will try to contact the poster and see if he knows what quality of mirror he bought.

[Windshift]

I wonder if this type of mirror would be of adequate quality for 25 times magnification ??

http://www.edmundoptics.com.au/optics/optical-mirrors/flat-mirrors/4-6-wave-first-surface-mirrors/32248/

it is 4-6 wave :shrug: and enhanced aluminum coated

[anj026]

Check out this link for some suitable mirrors at a good price in the US.

http://www.bigbinoculars.com/clearance.htm

[coldlegs]

You could try this mob.
http://www.firstsurfacemirror.com/glass

cheers
Stephen

[OzEclipse]

A good quality refractor objective is capable of up to 50x magnification per inch of aperture. 25x100 binoculars are of lower quality and are working at about 1/10th of that. You'll be looking at an angle much of the time so you need to at lease double the wavefront error. Maybe something better than this but you definitely don't need a 1/4 wave mirror.

If you want to get an idea on the cheap, try a piece of new dark tinted plate glass on the moon Jupiter or Sirius. Get one side sand blasted or grind it yourself then spray paint the sandblasted side with black paint. View them at different magnifications.

Joe

[Windshift]

The ones from "Big Binoculars" are 1/4 wave and should be great but they are 4 inch by 9.5 inch I could use 2 of these line them up right. With a 4 inch objective lenses I am guessing they will need to be absolutely perfectly aligned.
I saw the ones at edmund optics but wasnt sure if 4-6 wave was enough.
I emailed FSM to try establish what quality their mirrors are.
Graham