Originally Posted By: rafowell
> Is floatation important?
Malcolm Murray, who is probably the most dedicated signal mirror maker I know, makes both floating and non-floating mirrors.


Ive spoken with him - a genuinely nice man.

Originally Posted By: rafowell

> What about the aiming devices?

> The retro reflective mesh-type aiming devices seem to
> vary from mirror to mirror - lots of people who have
> used mine find them a bit difficult to use and
> difficult to find the fireball.

The retroreflective aimers do require training, and are a bit non-intuitive. However, the training need not take long, done properly, and a few minutes of practice should lock it in.

A good training aid is a patch of retroreflective material 100 yards away (the license plate of a (parked, unoccupied) car is good), and they should practice flashing in various directions relative to the sun - flashing towards the sun is easiest, and the retroreflector will only work out to about 135 deg from the line to the sun. I've made up portable retroreflective targets for my mirror testing and training using automotive reflective tape. Practicing with each hand is also a good idea - in an emergency, one arm may be pinned or broken.


I use the tail-lights on a car, which are retroreflective, as an aiming target.

I find the AMK aimer works over nearly the full 180 degrees. Havent tried the others over that range.

Originally Posted By: rafowell


> The one unusual one seems to be the StarFlash, which
> has some kind of lens element in there. It gives a
> bright fireball, but visibility through the device
> is really bad.
> What do people think about the aiming devices
> in their mirrors?

My favorite is the original 3M stainless steel mesh retroreflective aimer used in the old 3"x5" MIL-M-18371E glass mirrors - that's what is in my glove compartment, but 3M ceased production of that mesh in the 1970s. The "fireball" brightness was neither too dim nor too bright, and the apparent diameter of the "fireball" was just about exactly the 0.52 deg diameter of the sun.

The three issues I find with modern retroreflective aimers are:

(1) The brightness of the "fireball". Some are too bright in full sunlight (which I address by using sunglasses), and some are too dim in dim sunlight. This is a long recognized problem ( see this patent: http://www.google.com/patents?id=ys1DAAAAEBAJ ). Of the modern mirrors, I find the Starflash too bright, Rescue Flash, Coghlan's and Vector I brighter than I favor, the one Rescue Reflector I have a bit brighter, the 3"x5" S.I. Howard mirror aimer is "just right" and the 2"x3" S.I. Howard mirror on the dim side.

(2) The diameter of the "fireball" is about 3x the sunbeam diameter (1.5 degrees) in every modern mirror I've checked, unlike the old 3M mesh with the 0.5 diameter. This is also a long-recognized issue: it is mentioned in the cited patent above, and the USCG standard for "reflex type" (retroreflective) aimers calls out a maximum allowable diameter of 2 degrees: http://www.uscg.mil/hq/cg5/cg5214/survivalequip.asp#160.020 Basically this means that it does not suffice to get the "fireball" on target - you want the center of the fireball on the target.

(3) Clarity of the window - scattered light can be a problem -
another reason to keep the mirror clean and protect plastic mirrors from scratches. The USCG requires that cleaning cloths be provided with lifeboat mirrors. Another thing to check with the Rescue Flash mirror - make sure you peel back the transparent protective membrane when you use it (and sometimes it is on the back, for some reason) - the viewing is muddy with the membrane in place. It would seem that the size of the clear hole in the mesh would play into this, but I haven't done a careful study to determine my position on that.



My guess is that the 2 degree fireball comes from using road safety retroreflectors, which are optimised for a 4 degree viewing angle.

Thanks for your most informative and excellent posting.