[Tfug] Yet another optics question

[Bexley Hall]

Hi,

> >> With my totally unqualified opinion, I would go with what the
> >> guy in the climate change business, (ostensibly) said...
> >> 
> >> Just go with the 1460X six volt lamp as B&L designed.
> >> It's really common and easy to get by mail order. Its color
> >> characteristics are probably consistent. Kind of looks like
> >> an automotive lamp base with a flange...
> > 
> > The lamps run anywhere from $5 to $??? (some fools trying
> > to peddle them for $20!).  The old lamp was an "S1460" --  I
> > have not been able to get any clarification as to the
> > differences between the S1460 and 1460X... perhaps just
> > differences in manufacturer's part numbering schemes?
> 
> X indicates a long life version.

Ah, makes sense.  Though doesn;t relate to the prices you see!  :-/

> > The kicker with mail order is the $8 - $10 they want to ship
> > the 1 ounce bulb!
> 
> That's why I buy three. (As long the shipping doesn't
> multiply also.) If so, I look for another supplier.

Yes.  I just wonder how many lifetimes-worth to buy!

> > And, *using* the 20W device throws off a fair bit of heat
> > (the lamp is sited just below/in front of your forehead)
> > which makes it quite uncomfortable.
> > 
> >> Having said that, the lens assembly is probably like that
> >> of a photo enlarger condenser. As I understand it, it takes
> >> a point source and gives light focused at infinity. Good as
> >> an illuminator.
> > 
> > Yes.  My question is:  how critical is the location of
> > that point source?
> 
> I don't believe they would go to the trouble of fabricating
> a lamp with prefocused base unless there was a good reason

I expect some of this is attributable to the vintage of the
equipment (we're talking close to 50 years old, eh?).
And, its intended use -- whatever that may be :-/

I.e., I suspect my usage as a fancy magnifying glass doesn't
do it justice.  I haven't been able to exploit the "depth 
perception" that it affords in any noticeable way  :-/

I've already tried attaching a camera to one of the eyepieces
so I can view things on the screen instead of hunched over
the 'scope.  If this proves useful, all I need is enough
light to excite the camera.

> for it. If a convex side of the lens is toward the lamp,
> that cinches it for me. Nevertheless it will stlll work, but
> be less optimal.
> 
> >> If you wanted to play around have money to blow you could
> >> get a cheap high power LED emitter from a place like Deal
> >> Extreme. Place it at the focus where the lamp filament is.
> >> Give it an appropriate heat sink. The microscope power
> >> supply might work too.
> >> 
> >> Have fun!
> > 
> > I suspect I don't even have to go to the extreme of a fancy
> > emitter.  I tried an LED flashlight and it seemed to work OK.
> > Granted, more light would be nicer but I don't really see the
> > advantage of TONS of light (?).  The brochure explains that
> > it "helps cast shadows" (?)  OK, maybe that helps with depth
> > cues??
> 
> Wasting a handy flashlight might be considered extreme...

I just used the flashlight as a ready-made LED source.  I
pulled the ass end of the lamp assembly off, put the optics
half into the stereoscope and then held the flashlight in roughly
the position that the bulb would have been.  This was much
easier to maneuver the position and direction of the emitter
than a bare LED which would end up buried in the flesh between
thumb and forefinger.

> However, what might push me over the edge to commit
> flashlighticide is the idea of waiting three weeks for the
> $5-$7 emitter (shipped) to arrive from China.

No need to cannabilize a flashlight (though I will have to
remember that technical term for it -- may come in handy some day :> )
as I have a handy supply of LED's to choose from.

> www.dealextreme.com/products.dx/category.917
> 
> It's a tradeoff... Money for a known thing, or spending
> money and time to tinker with something else.

Of course!  You trade one type of unknown for another.
Maybe I'll see what's available in "bulb eliminators"
and see if there is something in a similar package style
that I can "drop in"