Reflection mirror for binoculars

[IanL]

Does anybody know what the technical name is for the unit that binoculars attach too and you look down with the binocular into a mirror at the sky above.
I would either like to make one or buy one. But as i don't know the correct name for this unit i can't do much research on it.
Cheers

Ian

[erick]

Here is a commercial version using it's own name "Sky Window".

http://www.tricomachine.com/skywindow/

Expensive, apparently - up to USD300 for mirror and mount.

Perhaps get an old photocopier mirror - I think they are front surface coated and should be cheap if not free?


OK a bit of searching leads to - try searching "binocular mirror mount"

The first hit has a set of links at the bottom:-

http://www.craigcolvin.com/Astronomy/BinocularMirror.html

[Blue Skies]

Those flat mirrors used in these set-ups are expensive, and with good reason! It is very hard to make a good flat, and to make a large one that is evenly flat all over is even harder. Getting an flat mirror out of an old photocopier is the way to go to make your own cheaply (I was told the newer copiers either dont have the mirrors or they have shrunk in size considerably).

[mrsnipey]

I believe they're called front-surface mirrors and there are a couple of suppliers of them on e-bay. I couldn't comment on their quality though.

[erick]

Here's a front surface mirror supplier:- http://www.fsmirrors.com/

Prices look very reasonable. Even the best and biggest is only USD91.95.

I'm tempted. Anyone else (best if in Melbourne) want to share shipping on a couple of mirrors?

[MrB]

Yes the photocopier mirrors are front surface and it's true the newer ones are small, about the same size as used in laser printers and flatbed scanners, about 250mm long but only 10 to 20mm wide, so pretty useless for binoculars.

Got one here from an old copier, it's about 60mm wide by 350mm long(guesstimate). unfortunately it's been knocked about over the years and has a few(!) blemishes and scratches.

[IanL]

Thanks for the info guys. Just what i was looking for. I rekon i will go down the make one myself road and see how it goes.

Many thanks for the info

Ian

[mick pinner]

l'd be very interested Eric.

[erick]

I've been thinking about it Mick. I need to experiment to work out what size mirror. I'd like to know whether I could get up to my 30x100s using such a system! (Yes, I know the mirror manufacturer says 18x is highest power recommended.) Trying to work out in my mind what the experiment needs to be to determine the size. The other issue would be the dew that would form on the sky-facing mirror. I'm wondering about that as well. So not quite ready to order as yet.

[mrsnipey]

You could put a dew heater on the back of the mirror.
A couple of resistors, a few hours soldering them together (for me anyway) and you're set. They're only 3-6mm thick so it wouldn't take much.

[erick]

Yes, that's what I was thinking. Thanks!

[Roger Davis]

A few blemishes and scratches wouldn't matter as they don't come into focus. You are, after all, focused on infinity not the mirror 100mm in front of your objectives! You don't need perfectly optically flat glass either, although it may help. A piece of float glass will be relatively flat enough to have aluminised and then used in this fashion.

[erick]

Thanks Roger - OK, I'm going to start checking out some truck rearview mirrors before I spend money on something special

[MrB]

True, but we're not focusing on either the primary or secondary mirrors in a newt either, so I figured they would still have an effect just as scratches/blemishes/dirt/dust on the mirrors in a newt affect contrast and resolution.
Whether it's perceptible thru the bino's, dunno. Might try it out.

[IanL]

Dew on mirrors. How does electric car mirrors work. Seems to clear heavey dew on mine in the morning and does a good job of it.

Ian

[bojan]

Blemishes and scratches on the flat mirror in front of the lenses will have exactly the same effect as if they were on the objective lens.

BTW, zenith prisms are much cheaper solution.... even if you need two of them (for binos), they will be cheaper than flat mirror.

[erick]

"Zenith Prism"? Bojan, I don't know what that is, but I can guess. I've done a bit of googling, but still cannot get a clear picture in my mind. Could you post a link I can check out, thanks.:)

[jjjnettie]

One of the Astro mags had a DIY on making one of these.
I'll go through my collection and see which issue it was.

[jjjnettie]

Sky and Telescope
Sept/Oct 2006

This might give you some ideas.:thumbsup:

[erick]

Jeanette, yes that certainly does give me more ideas. Many thanks. :)

[Globular3]

Hi Fellas

BBC Sky at Night January 2006 has a project you could consider.

Regards,

Glob. :hi:

45049 45050

[jjjnettie]

See how useful these magazines are! And my husband complains that I should throw them out when I finish reading them. Not bleeding likely.

[bojan]

Oh.. it must be my English.. :whistle: sorry
What I had in mind is just a prism or mirror for eyepiece, so that you can comfortably watch things around zenith. We used to call this "zenith prism".

http://shopping.yahoo.com/p:Tele%20Vue%20Optics%20DPC-2002%20Eyepiece%20prism:1993517359

The item on the link above is very expensive, though... I think I saw much cheaper.
And of course, to use eyepiece prism (mirror) some mods on binos must be done, which some people might not like to do. especially if the binos are expensive. But then, you will want high quality image.. and this can not be without high quality (expensive) mirror(s), for eyepiece or objective.

BTW...
have a look at this: http://www.surplusshed.com/pages/item/l2017.html
This (or similar) penta prism can be mounted in front of the objective lens.. and it is quite affordable...

Surplusshed has a variety of flat mirrors in stock... http://www.surplusshed.com/pages/category/flats_1.html

[Globular3]

Hi jjjnettie,

My wife wants me to throw them away too.This is why I'm scanning the articles into the computer. :lol:


Regards,

Glob.

[MrB]

I have the same problem. It's the difference between magazines that can be used as reference material and trash magazines like Womans Day/Vogue etc.
I have a mountain of Electronics and other Engineering magazines here dating back to the 70's, I still search through them for circuits and machining ideas etc.
Most reference magazines are collectable, deceased estate auctions and auction sites like Ebay regularly have large collections for sale.
(Type 'Model Engineer' into Ebay search)