Dec 012011
 

When caching at night the color in most things tends to go away. The blue light of the Moon doesn’t reveal a lot of color. There are two parts of the light spectrum that make for interesting cache experiences. Those are infra-red light and ultra violet light (it’s actually near ultra violet but we’ll let the science slip for a moment).

8 Segment Numbers in ultra violet light

8 Segment Numbers in UV Light

A little over a year ago Groundspeak added the UV attribute that can be assigned to geocaches. Since that time we’ve seen UV enabled caches grow. In a typical UV scenario a hint or coordinates are written in an ink that is UV reactive. The UV clue is sometimes written on the back side of a clue that is written such that it’s visible in white light. A cacher that is unaware of the UV attribute might be tricked by this approach.

In order to protect the UV inks from the elements we recommend placing them in non-UV blocking laminate. We carry non-reactive paper and self-sealing laminate pouches for this very reason. There is another way to provide clues using UV light and that is with UV reactive monofilament line.

8 Segment Numbers in White LIght

8 Segment Numbers in White LIght

We recommend creating eight segment digits like you see on a digital clock where some segments are not UV reactive and others are. Under white like the two lines are very hard to differentiate. Turn on a UV light and the correct coordinates pop out. In the pictures for this article the UV line is protected inside a sealable container. This is mostly for protection from the Sun’s rays. UV reactive features will degrade over time when exposed to sunlight. The UV line does not need to be protected from the elements, water won’t hurt it. You’ll also want to make sure that the cacher can’t see the backside of the coordinate segments. If they can see the backside they can see which segments use which kind of line and deduce the coordinates from that information.
The only special equipment you need to find a night cache with UV clues is a UV flashlight. There are a variety of UV lights available from small button lights to larger 3-in-1 lights. If UV caches are growing in your area then you’ll want to add one of these lights to your pack.

Coordinates Visible with IR Light

Coordinates Visible with IR Light

Coordinates Not Visible with White Light

Coordinates Not Visible with White Light

Caches that use infra-red (IR) light are harder to create and require special equipment to find them. An IR cache needs two components, an infra-red light source and an infra-red capable camera. Any remote control where you have to point it at the TV uses an infra-red LED. You can either take apart an old remote control or you can buy IR LEDs for about 50 cents each. We opted to buy them for our Lunar Lander BFL Boot Camp cache.

Now that we had an IR light source we needed to figure out what to do about a camera. I learned a while ago that webcams will pick up IR light but those aren’t too convenient to take into the field. I suppose if you had a little netbook that might work. I discovered that my BlackBerry makes for a decent enough IR camera for what we had planned. The facetime camera on an iPhone might work if you are patient. Many cameras have a built in IR filter. You can test your camera by viewing the front of a remote control through your camera as you push the buttons. If you see a light then your

Coordinates Visible with Infra-Red Light (close up)

Coordinates Visible with IR Light (close up)

camera will work to view IR light. You can also use cameras that have a “night vision” mode. As you can tell it’s not easy finding a way to view infra-red light. If you choose to build and IR cache it will be important to provide sufficient details in the description relative to your difficulty rating to allow people to find the cache. If you set your difficulty rating at 5 then you might not need to provide too many clues on how to solve the cache.

The trick to making and IR cache is finding plastic that is opaque to white light but easily transmits IR light.   Black or smoked plastics work best.  I used multiple layers of a red plastic.  It is very hard to pass white light through multiple layers but the IR easily passes.

We’ve just described a few ways that we have used ultra violet and infra-red to create caches. Hopefully these will be your starting point when you build your own creative night cache.

Remember to Grab a Light (white, UV or otherwise) and Cache at Night.

May 282011
 

Firetacks are a great way to make a night cache.  They are low tech and low maintenance.   The following tutorial will identify some things you should consider when using FireTacks.

The first thing you should do is make sure the area you are placing the FireTacks is accessible at night.  Many municipal parks are closed at dusk.   Look for signs at the trail-head to find the information you need.

FireTack Placement

geocaching firetack placement

Place FireTacks at eye level and avoid viewing obstructions

FireTacks use a retroreflective material.  This means that the  light shown at the firetack will be reflected back to the SOURCE of the light.  For this reason headlamps are recommended.   When using a headlamp your eyes will follow the beam of light.  The FireTacks may not appear as bright to someone standing next to the person with the light.  If you are using handheld flash light hold it to your eye level.    When placing your FireTacks pay attention to the area around the tree you are using.  Are there likely to be trees or bushes that grow up in front of the fire tack you have placed?  FireTacks should be placed at about eye level to minimize the issue of new growth.

FireTack Directionality

firetack placement blind spot

FireTacks have a natural blind spot.

The retroreflective nature of FireTacks combined with the diameter of the tree they are placed on create a natural blind spot behind the FireTack.   It is important to remember this when placing FireTacks in the bush.  The searcher can follow the FireTacks in to the cache but what do they follow to be back to the trail?   It is very easy to get turned around in dense foliage when searching for a cache.   If you are using flat trail reflectors you should place one on each side of the tree.  One for the way in and one for the way out.  This safety procedure means you will need more markers if you are using flat reflectors.

firetack placement egress

FireTack Placement for egress

With FireTack reflective trail markers you can place the marker perpendicular to the direction of travel.  In this way you can see the same reflector on the way in and on the way out.   When placing a complicated cache it is always a good idea to have someone test your geocache placement before it is published.   I have had to amend several cache placements based on tester feedback.  Keep in mind there is still a blind spot behind the FireTack.  If your path to the cache turns you may have to augment your egress path with additional FireTacks.

Variation One – Counting FireTacks

firetack counting

Count the number of FireTacks

There is more than one way to lay out a FireTack trail.  The most common is just lay out the FireTacks exactly where you want to lead the cacher.   A slight variation on this type of cache is where you count the number of FireTacks you see and at a certain number you turn or do something different.   Another way to  approach this type of cache is have the cacher go until there are no more FireTacks and then count back a small number.  At that point is where the cacher turns in.

In this example the cache location is marked by a different color FireTack.  You can use colors to mean different things.

The fact that you aren’t sure where you are going or if you’ve seen all the FireTacks makes this kind of night cache fun.  There is something about feeling a little lost in the woods, at night, that heightens the excitement.

Variation Two – Pattern Change

firetacks pattern change

Pattern change signals direction change

An alternative to making geocachers count FireTacks which is not as easy as it sounds.  Night Caching in the rain or the winter tends to inhibit one’s ability to accurately take notes.   Using a pattern change is a good way to tell cachers that you expect them to do something different.

As with the previous example extending the FireTacks past the turn off point adds a little more complexity to the cache, from the searcher’s point of view.

How far apart should you place your FireTacks?  There is no easy answer for this.  FireTacks are visible from hundreds of meters when using a bright LED light.    In practice the effective distance is much lower because of obstructions.  Trees, branches and leaves all play a part in making your FireTacks harder to see.   You should place the reflectors far enough apart that the searcher has to be on the look out for them but not so far apart that a small branch will obscure the view.   In the real use you can expect to place FireTacks every 40-80 meters.  This is another example of why having someone that didn’t help you place the FireTacks should test your cache before it is published.  Feedback from the trial will allow you to add more reflectors if required.

Variation Three – Color Change

firetacks color change

Change in reflector color indicates a direction change

You can take advantage of the fact that FireTacks come in multiple colors to introduce some complexity into your reflector trail.  Different colors may mean change in direction (that might include looking behind you),

You could also create two paths using different colored FireTacks.  One path could be a red herring and the other is the target path.  Adding a color hint to the cache description would let the cacher know which path to take.

The examples provided in this tutorial are a starting point.  Expand on these ideas to create a unique cache that other geocachers will enjoy finding.

Firetacks are made of durable materials and will work for many years.  Mother Nature has a way of reclaiming her turf and some firetacks will go missing.  While FireTacks are a low maintenance way to build a night cache you should expect to replace about 10% of the FireTacks each year.