having skipped around down my checklist of stuff (I think I'm on about the 147th reprioritization...) I've started looking at optics, both binoculars and various night vision stuff.

wondering if anybody had any thoughts on either of the above. - can't afford the sort of night vision stuff we had when I was in the army (guess we'll end up with russian made stuff)...and even plain old ordinary binoculars are pretty doggone expensive if you start looking for ones that are waterproof and shock-resistant!

comments? critiques?

Arlin

-- Arlin H. Adams (ahadams@ix.netcom.com), December 14, 1998

Answers

Here's a night scope:

http://www.ccrane.com/nitevisn.htm

Don't own one myself but Art Bell likes this one - have fun.

-- (infoman@web.com), December 14, 1998.

Do not bother with Gen I night vision crap. It is worthless. You must buy Gen II or III. I bought a Gen I NV 200 from Tasco for $250 and sent it back. It was crap.

-- Paul Milne (fedinfo@halifax.com), December 14, 1998.

My understanding is that these things take batteries. Unless you're using solar chargers, your use of such an optic will be short-lived.

David

-- David Hammer (davidone@worldnet.att.net), December 15, 1998.

I've got some low grade NV stuff. IMHO, one of the things you must look at is the batterys these things use. By some stroke of luck all my bad times electronic things use AA batterys. And ALSO by another stroke of luck I can recharge them on a solar charger.As far as the best power density for the buck, Radio Shack peddles a real good rechargeable battery. I forget the name but they are gold in color and run about 5.00 ea. You get what you pay for. I just got lucky and all my stuff will run off a AA. As far as the binoculars go the 7X40 EDF Aus Jena glasses I bought a few years ago are the best I've seen. The down side is they are 700.00 a copy now.

nine

-- nine (nine_fingers@hotmail.com), December 15, 1998.

Hi Arlin- This has been driving me nuts. Sometime last summer, I was thumbing through somebody's catalog, and saw a night vision binocular with a little "paddle" or lever on top. Pressing this repeatedly powered a little dynamo which supplied power for the intensifier circuits. No batteries. "Now that's clever", I thought and then I prceeded to focus on to other more urgent bits of gear.

Now, of course, I have no idea who the vendor or manufacturer is/was. has anyone else seen this item, or is this a symptom of some sort of PTSS (Pre Traumatic Stress Syndrome...)

BTW, a good source for this type of gear (as well as lots of other preparation related gear), is recreational boating. Two of the biggest discounters are West marine and E&B marine. They both have extensive websites.

Which perhaps I should look at.

Toodles

-- Lewis (aslanshow@yahoo.com), December 15, 1998.

Thanks to all of the respondents so far.

Paul is right - whatcha get often depends a lot on whatcha pay for, though for those of us on a budget being able to see 100 yards in the dark is better than not at all.

Dave and Nine thanks for the reminders concerning batteries and rechargers for this sort of stuff.

Lewis - do you by any chance have the urls for those web sites?

Thanks again, Arlin

-- Arlin H. Adams (ahadams@ix.netcom.com), December 15, 1998.

Binoculars

For a good all-purpose lifetime binocular, I have and recommend the USN Mil Spec 7x50 made by Fujinon (in USA). "The same binocular Fujinon supplied to the US Navy for demanding Sea duty. All lens and Bak-4 prism surfaces are coated with Magnesium Fluoride and sealed within light alloy housings from which all air, moisture, and contaminant have been purged by dry nitrogen. 100% waterproof and impervious to temperature extremes from -20 C to +70 C, the 7x50 BIF is designed for use anywhere on earth. Eyepiece has focusing range of +/- 4 diopters. The rubber eyepiece cups flip in or out for use with glasses or not. The Relative Brightness is 51.0 which is top rating. These are about $230 from Edmund Scientific (1-800-728-6999) at

http://www.edsci.com

How to read a binocular's power: The first number is magnification. The second number is the diameter in mm of the objective lens (the first lens).

The Exit Pupil: the diameter of the beam of light leaving the eyepiece and going into the eye. The larger the exit pupil, the brighter the image, and it's equal to the objective lens diameter divided by the magnification, in this case 50/7=7.14mm exit pupil. The pupil diameter in the normal human eye is 7 mm and in low light situations 7mm exit pupil is best to get the most light into your eye.

Relative brightness: the square of the exit pupil (7.14x7.14=51.0) the higher the number, the better for use in low light.

These binoculars do not have or need a 'focussing knob.' Once the eyepiece diopter is set for your eye, everything is in focus at all distances. I originally got these for observing the night sky, and they are also great for daytime use or theater etc. (I took them to Cirque Ingenieux, and was in row six, so a person's face would fill the view).

-- Jon (jonmiles@pacbell.net), December 15, 1998.

http://www.uws.com/Trijicon_ACOG_Scopes.html - tritium based non- battery very low light scopes.

http://www.botach.com/trijicon.htm - cheaper, and they have a lot of other stuff too.

-- Mitchell Barnes (spanda@inreach.com), December 15, 1998.

Those who don't understand night optics might wish to read:

http://www.intersci.com/nvexpln.htm

*RC

-- runway cat (runway_cat@hotmail.com), December 15, 1998.

Some of the best quality Ni-Cad rechargable batteries I've ever seen were at hobby shops---much better than Radio Shack. People who operate those radio-controlled models take their gear very seriously.

Hallyx

"Every time I think I've hit rock bottom, somebody throws me a shovel."

-- Hallyx (Hallyx@aol.com), December 15, 1998.

Re: exit pupils

Bigger is _not_ (necessarily) better.

The exit pupil of the binocular is the diameter of the light coming out of it toward your eye. But if _your eye_'s pupil is smaller than that light beam, the excess won't reach your retina to do any good.

IIRC, in young people, the average pupil almost always opens to greater than 7 mm in dim light, but as one ages this maximum pupilar opening declines. So after a while, ones eye can't make use of a light beam greater than 7mm.

By holding a millimeter ruler close to your eye as you look in a mirror in a dimly lit room, you might be able to measure your pupil's diameter. It's tricky -- there's a tradeoff between visibility of the ruler markings and dimness to coax your pupil to its widest.

I advise that in general, unless you're young consider any exit pupil in excess of 7mm to be of no benefit over one of just 7mm.

-- No Spam Please (anon@ymous.com), December 16, 1998.

NSP, very true about the exit pupil. Regardless of the exit pupil size, the apparent relative brightness will be further limited when the observer's pupil is less than the optic's exit pupil.

Normal pupil size with a shady or interior ambient light declines with age from about 7 in the 20's to 6 in the 40's to 5 in the 60's and settles down around 3 or 4 for the balance of life beyond the 60's. (This is sometimes called 'senile miosis' or 'age-related miosis'). In darkness or low-light the pupil will open up by 2 or 3 mm, increasing by less with age as well.

There are very few binoculars with an exit pupil greater than 7.14, in fact I have not seen any listed in three different sources. The 7x50 is the best spec for marine and night-time use. Compact, sports, and birding binoculars (which are almost always used during the day), have exit pupils in the range of 3 to 5 mm. The brightness index of these typically range from about 10 to 25 or so.

Another minor point is that the cornea and aqueous (the clear ocular media anterior to the pupil) will magnify the apparent pupil diameter by 10%. To estimate the diameter without a ruler, consider the average adult iris diameter to be 12mm vertically, and if the pupil in daylight spans about 1/3 the diameter, then figure about 4mm.

Eye relief is also a parameter to viewing optics, and this refers to the distance from the last lens surface of the scope (the lens surface closest to the eye) to the apex of the cornea. Sport scopes typically have a 10 to 15 mm eye relief. The marine/nightsky type of binoculars (7x50) will have 17 or 18 mm eye relief, sometimes as high as 22mm. This is important to consider if you wear glasses. To see the effect, go to most any camera or sports store to try the scopes out. That way you'll have a subjective idea of what all the specs mean. Other parameters besides magnification, objective diameter, exit pupil, brightness index, and eye relief are: angle of view (typically 5 to 7.5 degrees), field of view at 1000 yards (100 to 150 yards), focusing (center or individual), lens coating, prism type, nitrogen filling (which prevents fog and moisture problems), dimensions, and weight.

Another consideration is that magnifications over 7 are hard to hold stable, but if you have the budget consider the Canon Image Stabilizer Binoculars in sizes 10x30, 12x36, or 15x45 ($600 to $1400). Orion Telescope and Binocular has these; see http://www.oriontel.com for more info.

-- Jon (jonmiles@pacbell.net), December 16, 1998.