One solution is to use a spotlight with a 75w or a 100w bulb but use a
battery pack
with a dimmer switch. This means you can spend most of your time
spotlighting with something equating to around 30w power which is plenty for
most forest and woodland habitat: not only does your battery lasts longer,
it might also mean you see more animals per hour anyway -- I remember
something from a study on the Atherton tablelands that claimed spotlighting
with a 30w bulb was more successful than a 100w (that is mammals were hiding
from the brighter light).
But there are times when you need a bit more oomph ... that eyeshine in a
tree 100m across the clearing .... at which point you can whack the dimmer
switch up to full blast.
Lawrie makes some good points about battery life and using the halo
('penumbra' rings a bell from physics lessons) to good effect. I agree with
him that I find very little difference between 75w and 100w systems.
Red filters are supposed to work well with spotlights because many animals
cannot detect red light...though I have never tried it. I suspect they'd
be lousy for getting eyeshine but once you have found a critter then
sticking a filter on top of the spotlight means you can probably observe it
for as long as you want without giving it temporary blindness (I've no idea
if this applies to birds but it is true for many mammals I think)
Jon
-----Original Message-----
From: Lawrie Conole <>
To: Andrew Taylor <>; michael hunter
<>
Cc: <>
Date: 28 January 2002 17:25
Subject: Spotlights-RFI
>A few random (and perhaps incoherent) thoughts on spotlighting hardware ...
>
>The first thought that always comes to my mind when this discussion topic
>comes up is "How powerful a spotlight is actually necessary to observe
>wildlife at night?". Is a 100 Watt (100W) light any better than a 75W? -
at
>least in terms of what use a human eye can make of the output of either
>unit.
>
>I'm not too sure about the candlepower unit and what that means in the real
>world, but spotlights are generally categorised by manufacturers in terms
of
>the power (in Watts) of the globe. Design of the reflector and/or globe
>might vary the light output from otherwise similar globes rated at the same
>wattage. One manufacturer of spotlights in Australia sells handheld units
>with a number of different globes - 30W, 40W, 50W, 75W and 100W.
>
>Up until now, I've always used an old 30W/*6V Watco spotlight, and found it
>more than adequate for all forest and woodland spotlighting. It's a bit
>under powered in grassland and other very open habitats, and the light is
>relatively yellow compared to other systems I've seen in action alongside
>it. I recently upgraded to a 75W/*12V system with a halogen globe, and
have
>been very impressed with its performance in the field so far. This is a
>standard configuration from that manufacturer, otherwise I'd probably have
>gone for a 40 or 50W. I compared it with a 100W system, and judged that
>there was no measurable benefit from the extra 25W of power consumption,
ie.
>my eye was unable to see any further or better with a 100W vs. a 75W light.
>
>The 75W light puts out a prodigious amount of very white looking light - so
>I've also purchased a diffusing filter to scatter the light more when
>working close up to animals. Jack Pettigrew did make the point that
>although powerful spotlights might not cause permanent damage, temporary
>blindless might be caused, and this may make the animal more prone to
>predation. I tend to exercise the precautionary principle, and put as
>little light on the animal as is necessary to identify or observe it. Most
>lights put out less intense, scattered light as a halo around the
>concentrated spot, and I find that it's easy to use the spot to find the
>animal, then the duller halo to observe. I udge that I'm having the
minimum
>impact possible on the animal by doing it this way, and it is no less
>effective for the purposes of survey/study, etc.
>
>Battery life and size are important matters that people may sometimes
>overlook. If you are intending to use the light only from the car (plugged
>in to the cigarette lighter), then it really matters little how power
hungry
>the light is. If you are going on foot carrying the battery, then it makes
>a big difference. With a 75W or 100W, 12V light, in order to be able to
>spotlight continuously with just one battery for about 1-2 hours, you'll
>need something like a 17A/h battery. These are big and heavy, and you need
>to try one out to see if you can carry it over uneven ground for any length
>of time. A much lighter 7A/h battery with 75 or 100W light would last
about
>20-30 minutes, but would be a great deal easier to carry. A 7A/h battery
>with a 30W light would last maybe 1.45 hours, and would be quite effective
>in most forest/woodland environments. Choosing a battery is at least as
>important as choosing a light - the combination of the two makes a great
>deal of difference in terms of how long you can be out there before needing
>a fresh battery, or perhaps a pack animal to carry the thing!!
>
>When I started spotlighting about 25 years ago, we carried standard 6V lead
>acid motorcycle batteries in wooden boxes. These things leak whenever
>they're tipped a bit off vertical, which led to lots of holes in clothing
>etc. from the acid. Most people use sealed lead acid batteries these days,
>and I'd recommend them very highly. They're relatively inexpensive, they
>don't leak in use or while bumping around in the car, and are quite durable
>if looked after nicely! They're available in both 6 and 12V formats, which
>the old wet cells were not - hence me starting out with a 6V system. 12V
>batteries can be charged from the car system with a relatively simple
>intermediary device - 6V isn't as straight forward unless you have an old
>Volkswagen!!
>
>L.
>
>+++++++++++++++++++++++++++++++++++++++
>L A W R I E C O N O L E
>2/37 Myrnong Crescent, Ascot Vale, Victoria 3032 AUSTRALIA.
>Phone AH (03) 9370 3928; Mobile (0419) 588 993.
>E-mail:
>
>Senior Zoologist
>Ecology Australia Pty Ltd
>88 B Station Street, Fairfield, Victoria 3078 AUSTRALIA
>Phone BH (03) 9489 4191
>E-mail:
>+++++++++++++++++++++++++++++++++++++++
>
>
>Birding-Aus is on the Web at
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