The NHBS guide to buying a hand lens

Hand LensThe possession of a hand lens is one of the defining characteristics of a naturalist.

We use them for everything from peering at beetle genitalia and examining floral characters, to examining the arrangement of teeth in small mammal jaw bones. There are a wide variety of hand lenses on the market so how do you decide which lens is best for you? This article contains all the information you need to make an informed choice about which hand lens is most appropriate.

Glass versus plastic lens?

The optical lens in a hand lens can be made from glass or plastic – the plastic lenses are generally more affordable and lighter but are of lower optical quality and more difficult to clean. Good plastic hand lenses, such as the Plastic Double Magnifier, are perfect for youth groups and schools.

How many optical elements?

Canon 400mm

An element is an individual piece of glass within a lens. When you look through a high quality camera lens you will typically be viewing what’s in front of the lens through four to six lens elements, as well as other elements used for focusing and zooming (see image below right).

Paul Canon EF 400mm f/4 DO IS USM By Paul Chin

Hand lenses are constructed with one (singlet), two (doublet) or three (triplet) lens elements. Each element is specially shaped to correct for a particular type of optical distortion so the more elements, the higher quality the image.


A 10x magnification hand lens will be more than adequate for most purposes. Higher magnification lenses tend to be harder to use but are very useful for viewing extremely small objects. If you are unsure of which magnification you need, or think you may need several different lenses, you should have a look at the x10 and x20 Duel Singlet Loupe or even the x3, x4 and x5 Triple Loupe.

Lens diameter

Large diameter lenses provide a wider field of view which means that they are easier to use but they are slightly more expensive to produce.

How hand leOpticron Hand lens, 23mm, 10x magnificationnses are named

Hand lenses are named like binoculars, with both the lens diameter and the magnification included in the name. e.g. the Opticron Hand lens, 23mm, 10x magnification has a 23mm diameter lens and provides 10x magnification.


Using your hand lens

Finally, a quick note on hand lens technique. To use your hand lens correctly (this is particularly important when using high magnification lenses) hold the lens close to your eye and then either a) move the subject closer to your eye until it comes in to focus or b) move your head (and the hand lens) closer to the subject until it comes into focus. It’s easy with a little practice so don’t get put off if you find a new hand lens difficult at first. Expect to get close up to what you’re examining – it’s quite common to see naturalists crawling around on the ground to get close to a plant they’re identifying.

Keeping your hand lens safe

It can be very hard to find a much-loved hand lens dropped in long grass or woodland. To prevent this traumatic experience, we recommend a lanyard for your hand lens – this has two functions: a) if you have it round your neck you won’t drop it, and b) if you put it down somewhere the bright blue lanyard is easy to spot.

The table below provides a guide to the hand lenses sold by NHBS. More information and specifications of each can be found on the website.

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Getting started with the SM2BAT+ bat detector

SM2BAT+The Wildlife Acoustics Song Meter SM2BAT+ is a passive ultrasound recorder that can be left out in the field for long periods of time to record ultrasound at frequencies of up to 192 kHz. The SM2BAT+ comes packaged in a plain green weatherproof box making it easy to position discretely without the need for expensive or time consuming efforts to weatherproof/camouflage it. Setting a bat detector up for passive monitoring can be a slightly daunting experience for the first time user so we have produced an annotated internal diagram (see below right – click the image to enlarge) and this blog post describing our experiences getting started with the SM2BAT+. Despite feeling a little scared at Inside the SM2BAT+the sight of circuit boards I am pleased to report that I found the SM2BAT+ to be very user friendly – read on for our idiot’s guide to setting up an SM2BAT+.

Getting started

The first thing you will need to do is insert four D-Cell batteries into the slots. A number of variables affect battery life including the quality/type of the battery, temperature, and the recording mode. The manual produced by Wildlife Acoustics suggests that if high quality Alkaline D-Cells are used at 20oC then you should get 130 hours recording time at 192 kHz mono and 100 hours recording time at 192 kHz stereo or 384 kHz mono when using in WAV mode and over 300 hours of recording time when using ZCA mode.

Next you will need to insert an SDHC card into one of the Flash Card Slots. Wildlife Acoustics recommend using good quality SDHC Class 4 or Class 6 cards and a single 32GB card should easily last a minimum of 2 weeks.

How to programme your SM2BAT+

Now it is time to programme your SM2BAT+. Setting up a simple schedule is very easy, switch the unit on by pressing the WAKE/EXIT button. Once it has woken up you will be able to see whether your SDHC card has been accepted and how much spare memory is available. To programme your unit press the SELECT button to see the menu; then to scroll through the menu options press the UP and DOWN buttons, press BACK to move back up a level, and press SELECT to move left and/or toggle through a list of options.

Below left shows a schematic (click to enlarge) of the Song Meter Main Menu and includes the settings I used for a trial run of the SM2BAT+. The first page of the menu includes three options – Schedule, Settings and Utilities. Setting the schedule could not be easier, press SELECT when the cursor is flashing next to Schedule, then press SELECT again, update the time using the UP and DOWN buttons then press SELECT again to keep moving to the left filling in the details as you go. You will see that I have set our SM2BAT+ to come on at 20:30 and record for 10 hours.

SM2BAT+ SchematicPress BACK to come out of the Schedule menu and then DOWN to move to Settings, then SELECT again to enter the Settings menu. For a quick test of the unit you will need to set the time and date using the UP, DOWN, SELECT, and BACK buttons as before. Finally select AUDIO to check the recording settings. In my test run I opted for a Sample rate of 384000 (384 kHz) because we have lesser horseshoe bats in the Totnes area. This is because the maximum frequency recorded is equal to half the sample rate – consequently, at a sample rate of 384 kHz the SM2BAT+ will record ultrasound at frequencies up to 192 kHz on one channel (perfect for lesser horseshoes that echolocate at around 110 kHz). If you want to use both channels (i.e. two microphones) you have to record at a maximum sample rate of 192 kHz. Although you may miss lesser horseshoe bats the big advantage of using both channels is that you can separate the microphones (using extension cables – available from NHBS) by up to 100m, effectively doubling the number of bat detectors you own for the price of a couple of cables. Alternatively you can separate the microphones by 10-20m to measure flight directionality along a linear feature.

Next you need to select which channel to record on. Under Channels I selected Mono-L to record from the left hand microphone input. For Compression I selected Off which means that the SM2BAT+ is in trigger mode and records individual WAV files for each trigger.  Analook users may prefer to use the ZCA option which records individual ZCA files for each trigger. Alternatively, some users may prefer the WAC0 option which produces a continuous compressed WAC file for the duration of the recording period (actually the files are size limited so I found that 1hr 33min chunks are produced). That’s it… all you need to do now is take your SM2BAT+ to your field site.

Field set-up

Once at your field site check the settings and do a test recording. To do this plug some headphones into the headphone jack and start recording by pressing both the UP and DOWN buttons simultaneously. Once the recording has started press SELECT to view the channels and then make some ultrasound by eg. tapping your fingers and thumb together or rattling some keys. If all is well then put your unit back to sleep, seal the weatherproof enclosure (don’t forget to take a screwdriver with you) and plug your microphone in to the left hand microphone input (using your extension cable makes hiding the unit much easier). It is worth remembering that the indicator LED is visible when the lid is on so make sure this cannot be seen by passers-by.

Data analysis

Downloading the data is also easy – simply remove the SDHC card and place it into an SD card reader. To analyse the data I used Pettersson’s BatSound v4.12. My WAV files opened immediately and I used the Close, open, next button to scroll quickly through the files so the analysis was quick and painless. On my first night I recorded soprano pipistrelle and greater horseshoe bats in the centre of Totnes.

Available now from NHBS


New user info for the Echo Meter EM3 Bat Detector from Wildlife Acoustics

We recently received the following information from Wildlife Acoustics to help you get the most out of your Echo Meter EM3 Bat DetectorEcho Meter EM3


Dear EM3 User,

Congratulations on your purchase of the Wildlife Acoustics Echo Meter EM3 Bat Detector! We think the EM3 represents the most advanced technology available in a handheld detector and provides unparalleled functionality at a fraction of the price of other professional detectors. A piece of equipment with this much technology does, however, have a learning curve. To help you master the skills necessary to get the best performance from your new detector we would like to share some tips and best practices (and common mistakes) we have learned since its release. We think the following information will help you get the most out of your EM3.

Update your firmware!

We are constantly making improvements to all of our products via firmware updates. These improvements can include important bug fixes as well as new functionality or requested features. We provide these updates at no charge to add further value to our products. Please go to to download the latest version of firmware and read the release notes on what has changed. The current firmware version loaded on your Echo Meter can be seen on the top left of the “splash screen” at start-up. At the time of this email we are on version 1.1.2.

Introducing a whole new approach to zero crossing

With this email we would like to introduce a free new software we have developed called Kaleidoscope and a whole new approach to zero crossing. Kaleidoscope converts WAV or WAC files into zero crossing files with incredible quality and speed. In fact the results are superior not only to any existing zero crossing conversion software but they are also superior to what would be possible with native zero crossing. Don’t just trust us, try it and let us know what you think!

The conversion is incredibly fast. It can convert several nights of data in just a few minutes. This represents a 30x improvement over our existing WAC2WAV software, which was on par or faster than any other conversion software.

Kaleidoscope can even convert zero crossing to WAV (yes you read that right). This is a great way to be able to convert your Zero Crossing files into audible WAV files. Kaleidoscope is available on the download page of our site (see the link above). It is currently in Beta and will ultimately replace our WAC2WAV conversion software.

What about native zero crossing?

As you know the EM3 also has the ability to record zero crossing files natively and you might be wondering how that compares to full spectrum files converted to zero crossing using Kaleidoscope. We feel the results from Kaleidoscope are superior to native zero crossing, whether it be on the EM3 or any other zero crossing recorder. The zero crossing results from Kaleidoscope are so good and the conversion is so fast that we are now recommending this as the best approach. Feel free to test this out if you need convincing. You can record simultaneously in WAV and zero crossing, convert the WAV files to zero crossing and compare the results.

If you do prefer to stick with the native zero crossing, here are a couple tips to get the best results. Always be sure to adjust the zero crossing sensitivity (just hold down the speaker button until you enter FDAdj made). The default setting is quite high and will not pick up many bats. Also, always adjust the setting using headphones. If you adjust using the speaker, the feedback from the speaker will result in a much higher than optimal setting. You want to set the level just to the point where you only hear a little noise rather than a constant din of noise. This should be three or four squares on the display.

We have found that the GPS attachment for the EM3 can introduce noise into the zero crossing circuit. This necessitates setting the sensitivity up a couple squares. For best zero crossing results with the GPS please consider our recommendation to use WAC and convert using Kaleidoscope. As an added bonus, when using the GPS in WAC mode, you will retain not only the location of every recording but the entire transect path. Kaleidoscope can output the recording locations and the path during the conversion process into a KML file compatible with Google Earth!

Try Real Time Expansion (RTE)!

We have included three monitoring modes in the EM3. Heterodyne and Frequency Division were included for those familiar and comfortable with those technologies. We also developed our own novel technique for monitoring called Real Time Expansion. This technique provides all of the frequency and timing information of the original call. It has superior tonality to Frequency Division and does not require tuning like Heterodyne. We consider it the best monitoring method on the market. If you have been using Heterodyne or Frequency Division, we strongly encourage you to try RTE.

Screen adjustments

Remember that you can adjust both the brightness and contrast of the screen to suit any lighting condition and preference. If you momentarily press and release the Display button, you can then adjust brightness using either the Plus and Minus buttons or Up and Down buttons. The contrast is adjusted using the Right and Left Arrow buttons. You can also switch between “black on white” and “white on black” display modes by holding down the Display button.

Getting back to the present

We have seen a common confusion where users are monitoring for bats while scrolling back through the spectrogram buffer to look at past calls. When you are viewing calls at or near the end of the buffer and a bat comes along the end of the buffer begins to disappear as new data is written to the front. This can give the illusion that you are viewing “the present bat” because the buffer begins to move making the spectrogram scroll. To get “back to the present” to see the new bat calls being written to the spectrogram, just double click the X/Y button.

Use headphones for best sound quality

The speaker on the EM3 was included for convenience and can provide an excellent monitoring experience, but for the very best quality, we encourage you to try monitoring with headphones. Headphones have better fidelity, greater volume and more bandwidth than the speaker so they really bring the bat playback to life.

Always use the EM3 with charged batteries

The EM3 monitors battery level and automatically shuts down when the battery is near depletion. This prevents the circuitry from getting into a state where it is not appropriately powered resulting in erratic behavior. But if you power up the unit with nearly depleted batteries, it will exhibit this erratic behavior before the detector gets the chance to determine that the batteries are nearly depleted. It will be stuck in bad state and you will not be able to power down without removing a battery. Batteries tend to regain voltage over short durations of no use. This means that if you do not charge the batteries after using them and then power up the detector after some time, the batteries will have regained just enough voltage to power up but not enough to supply proper power. Also be aware, that the EM3 is never truly off, but in a deep sleep state so as to be able to retain the spectrogram buffer and clock. After a few weeks the batteries will deplete even after no use.

If you get stuck, reset

If, while using the EM3, you find that you have made a bad setting or gotten into an unknown state you can always reset the unit back to factory defaults. You simply pop a battery from the battery tray and reinsert while holding down the left button. Continue holding the button until the splash screen appears. Sometimes an apparently broken unit can be something as simple as the brightness having been turned quite a low at night appearing as though it won’t power up in the morning! This procedure would reset the brightness setting to default, apparently bringing the unit back to life.

Happy detecting.

Wildlife Acoustics, Inc.

Available now from NHBS

NHBS Equipment Team:

+44 (0)1803 865913

Five reasons you will love the new Habibat Bat Box

Wall-incorporated Habibat - artist's impression1. Artificial accommodation designed for bats

The Habibat is a large bat box made of insulating concrete with an internal roost space, which can be incorporated into the fabric of a building as it is built or renovated. Its single chamber is internally divided by inverted V wedges to increase surfaces for bats to roost against and to allow them to move around.

2. Habibat boxes can be faced to match the buildingHabibat Bat Box - Staffordshire Smooth Blue Brick

Two stock colours: Staffordshire Smooth Red, and Staffordshire Smooth Blue brick, are complemented by thousands of bespoke colours of facing brick, stone, granite, masonry, slate, terracotta, tile and timber finishes.

Habibat Bat Box - Custom Brick Facing3. Habibat is a unique partnership with the Bat Conservation Trust

The Bat Conservation Trust will be collating information on the use and installation and of Habibat boxes. In addition, the Trust has contributed to the design of the box, and a number of Habibat variants will be tried and tested to continue the development of the product.

4. Habibat is a versatile bat box system

We can supply quotes for joining multiple Habibat boxes or other bespoke requirements.

5. Habibat is made to standard brick dimensions

Habibat is simple to incorporate into walls as it has the same footprint as a standard UK brick (215mm wide x 103mm deep) and can be matched in height with six courses of bricks.

Find out more

Triple Chamber Bat Box available from NHBS for the first time this autumn

Triple Chamber Bat BoxIntroducing the Triple Chamber Bat Box


NHBS’s new Triple Chamber Bat Box is available for the first time this autumn. The new bat box has three large chambers providing its inhabitants with a huge living area (compared with most other wooden bat boxes). Consequently, they are particularly well-suited to large colonies, including maternity colonies. Most crevice-dwelling bat species are likely to be attracted including Pipistrelles, Brown long-eared bats, and Daubentons. Species which may sometimes use these boxes include other Myotis species and Noctules.

Triple Chamber Bat Box interiorThe boxes are very deep, providing the bats with a stable draught-free environment and plenty of space for individuals to cluster together or disperse, and for the sexes to mingle or separate. Triple chamber boxes have proved to be a success in the U.S. where it is thought that the extra space provided gives bats the room to interact more normally. The boxes open at the top and are 60 cm high with a small aperture at the base of the box for bats to enter and exit. They are narrow (14 cm) and can easily be hung on both trees and buildings. The Triple Chamber Bat Box is constructed from European Redwood harvested from a sustainably managed forest.

Available Now from NHBS