Another question on moth traps (1 Viewer)

Surreybirder · Feb 25, 2004

Someone has generously offered to lend me a 125 MV light moth trap.
I have a question that I'd be grateful for some advice on.
I live directly under the flight path to Gatwick airport which is only a few miles away, and planes pass very low overhead sometimes.
Does anyone know whether a very bright light is likely to cause problems, either from the airport authorities or the security officials?
This may seem a silly question but there have been stories on ukmoths yahoogroup of police helicopters descending on moth trappers, and I'm in a potentially sensitive area. Any advice?!
Thanks,
Ken

simon&emma · Feb 25, 2004

I have a friend who records in a similar situation as yourself and he doen't have any problems. Please consider that the 125watt mv lamp is basically the same as the ordinary street lamp. I order my lamps through the company I work for and they are just MBF mercury vapour street lamps. If your worried about the brightness of the bulbs then you can use a Black Lamp which would fit into the same light fitting as your mv lamp. This would emit no light at all, but your catch would definately be a lot lower.

So all in all I really don't think you have anything to worry about. Give it a try when the weather warms up again !!

Hope this helps and good luck.

Simon

Surreybirder · Feb 25, 2004

Thanks, Simon.
One of our neighbours has got three lamps in his garden (sodium but bright), so I guess I won't be alone!
Keep up the good work on your web site!
Ken

harry eales · Feb 28, 2004

Surreybirder said:
Someone has generously offered to lend me a 125 MV light moth trap.
I have a question that I'd be grateful for some advice on.
I live directly under the flight path to Gatwick airport which is only a few miles away, and planes pass very low overhead sometimes.
Does anyone know whether a very bright light is likely to cause problems, either from the airport authorities or the security officials?
This may seem a silly question but there have been stories on ukmoths yahoogroup of police helicopters descending on moth trappers, and I'm in a potentially sensitive area. Any advice?!
Thanks,
Ken

Hi Surreybirder,
As an ex pilot I can say that a 125w MV lamp would not, under normal circumstances cause a problem, there are usually a lot of bright lights around an airport. However, as its one of the airports servicing London, security is likely to be high. I would suggest you ring the Airport Security before lighting up and let them know what you are doing, and exactly where you are. You may well bet a visit by the local plod, but are unlikely to get an armed response team arriving all ready to have a shoot out with terrorists.

Have fun,

Harry Eales.

Surreybirder · Feb 28, 2004

harry eales said:
You may well bet a visit by the local plod, but are unlikely to get an armed response team arriving all ready to have a shoot out with terrorists.

Have fun,

Harry Eales.

Thanks, Harry.
An armed response team would be a good 'year tick'!
Ken

simondix · Mar 1, 2004

In the summer when he tells us he caught a Tiger Moth will we know which one he means.

Surreybirder · Mar 14, 2004

I'm almost ready to go... except it turned out to be an 80W MV light.
It's got a small rain shield (about 6" diameter) over the bulb. Could someone please tell me how critical it is to keep the bulb dry. For example, this evening is mild but windy with intermittent rain. I cannot see the existing shield keeping every last drop of water off the bulb.
If I decide to try and extend the shield (which at the moment is a flat, circular piece of perspex) any tips on what it the best way of doing this?
Thirdly, what can you use to cut perspex?
Sorry to raise so many questions but I'm new to this.
thanks,
Ken

simon&emma · Mar 15, 2004

Ken,

You'll be fine not covering a 80w MV light. I run several 125w lights and I never cover those except in extremely heavy rain. I think in fifteen years recording I have only ever had one crack through rain and that was from very big drops falling from the trees. The only bulbs that you really have to cover are the black bulbs, which run very hot due to the light filter that coats the glass.

If you really feel happier covering it then a medium sized pyrex bowl is very good, but I really don't think it's worth worrying about especially with an 80w bulb.

Thanks

Simon

Surreybirder said:
I'm almost ready to go... except it turned out to be an 80W MV light.
It's got a small rain shield (about 6" diameter) over the bulb. Could someone please tell me how critical it is to keep the bulb dry. For example, this evening is mild but windy with intermittent rain. I cannot see the existing shield keeping every last drop of water off the bulb.
If I decide to try and extend the shield (which at the moment is a flat, circular piece of perspex) any tips on what it the best way of doing this?
Thirdly, what can you use to cut perspex?
Sorry to raise so many questions but I'm new to this.
thanks,
Ken

Brian Stone · Mar 15, 2004

Rain shields

I have heard conflicting views on the need to shield MV bulbs from rain. The fact is there are plenty of people who have run bulbs for years without losing one but there are a few (enough) who have first hand accounts of bulbs breaking. Some of these stories were enough to ensure that I now always have protection on my bulb. Essentially bulbs can explode (and have done in the past), sometimes violently. The chances may be slim, but the consequences of being unlucky enough to be around when this happens make caution worthwhile. I just place an old caffetierre jar over my bulb resting on two plastic clips to raise it up to the right height.

simon&emma · Mar 15, 2004

That is a very good point that Brian has brought up. If you do manage to be unlucky and have a bulb that breaks, they can explode as they are high pressure lamps. I was involved in a public moth recording event last year and for saftey reason it was very apparent that the lamps should be covered. Certainly if the same happens this season then I shall cover the lamps with a pyrex type bowl.

I think the risks are small, but you never know !!

Cheers

Simon

Andrew S · Mar 15, 2004

But doesn't the glass cut out most of the UV light that attracts the moths?

simon&emma · Mar 16, 2004

I know thats certainly the case with the 125w black bulbs as all the visible light is filter out, but I'm not aware that it's such an issue with the 125w mv white lights. It may well be compensated with the light intensity which has a lot to do with the effectiveness of a light trap. A covered 125mv lamp still catches a lot more than a uncovered 125w black lamp.

Cheers

Simon

harry eales · Mar 16, 2004

I have never found it necessary to provide a rain cover for a standard MV bulb. I ran one trap in my garden for over 10 years, in all weathers including heavy downpours of rain and even occasionally snow. Some bulbs did give up and stop working but that was due to wearing out rather than cracking.

You are far more likely to break a bulb by moving the trap too soon after you have switched the lamp off. The fillaments remain very hot and fragile for several minutes after shutting down and are very easily broken.
This is especially true when working the trap away from home, and are in a bit of a hurry to 'pack up'.

I use a Robinson Trap and I have a home made extention fitted to the vanes which rise some 18" above the trap over the bulb so a rain shield would be rather useless.

I have used 'Black Light' bulbs, which I found rather more affective than the statistics indicate, again I had no problems with them cracking, but I have not used them in heavy rainfall. It was simply the price that put me off them.

Any rain cover made of glass will filter out much of the MV light and the resultant catch will be smaller than that obtained if no rain shield is used. Pyrex bowls are usually recommended as protection simply because they can be used in higher temperatures than ordinary glass and are not likely to shatter. Any ordinary glass bowl used as a rain shield could break and this could lead to damage to the MV bulb. So, if you must use a bowl as a rain shield the extra money spent on purchasing a pyrex bowl may save you buying a new bulb.

scampo · Mar 16, 2004

Harry

I'm intrigued. My son uses a 250w bulb in our home-made trap - and it is very effective; but he also has a low voltage (12v) UV tube which he leaves on all night.

Are you saying that the 250w bulb will not shatter if it rains? And also - what about the voltage in the wet? Isn't that also a danger?

I'd be grateful for your advice.

Andrew S · Mar 16, 2004

I usually run my trap (125v MV, no rain cover) overnight, with no adverse effects from the rain (although I don't put it out if it looks particularly rainy). It has survived some heavy rain.

I read somewhere that the problem is rain and a strong wind, so that just one side of the bulb is cooled by the rain. However, if there is something in this, don't see why rain cooling just the top of the bulb when there is no wind wouldn't give problems - unless the radial symmetry helps then. Or, maybe it's something to do with rain getting to the bottom bit where the glass meets the metal?

Don't really know...

scampo · Mar 16, 2004

Are the electrics safe in the rain, though?

Andrew S · Mar 16, 2004

The choke box I got is apparently completely waterproof (and looks it), and is left out in the rain.

Not sure what the other problems would be - if both the outer and inner glass envelopes on the bulb shatter then the electrodes (presume there are electrodes) may be exposed. But you could see this and would presumably turn off the power before sticking your finger in. If they shorted out, presumably the worst thing that would happen would be that the fuse blew, but suspect the choke would prevent that (but only have a nebulous idea of how the choke works).

As you've probably gathered these are just my non-expert thoughts - I'm not an electrician!

Andrew

Brian Stone · Mar 16, 2004

On the potential for bulbs to explode, which could conceivably result in you never seeing another moth again, see:
http://groups.yahoo.com/group/ukmoths/message/22587

I think the archive is open to non-members. If not shout and I'll cut and paste.

On electrics, my mains connection is via an ELCB and any junctions outside (including the choke box - whatever that does) are under a cover (weighed-down bucket or similar).

scampo · Mar 16, 2004

It's members only. I think the choke converts the power from AC to DC, but I might be wrong.

harry eales · Mar 16, 2004

scampo said:
Harry

I'm intrigued. My son uses a 250w bulb in our home-made trap - and it is very effective; but he also has a low voltage (12v) UV tube which he leaves on all night.

Are you saying that the 250w bulb will not shatter if it rains? And also - what about the voltage in the wet? Isn't that also a danger?

I'd be grateful for your advice.

Hi Scampo,
I have never used a 250w MV bulb only 125w, so I have no experience to draw on here, sorry. When I'm at home using the trap I keep the choke in the living room and run the cable down the garden to the trap which is some 30 yards from the house. At the trap I have a single waterproof connection. Should a bulb 'blow' I trust the 'in line' circuit breakers to work. If a problem arises I would always switch off the electric power before further investigation.

When collecting away from home the choke is always placed on a plastic base well under my motor vehicle out of the reach of any rain and off the possibly damp ground. All the connections from the generator, choke and trap are waterproof. I am shy of electricity, ever since as a small child I stuck a screwdriver into a two pin socket and switched it on. (You never forget a lesson like that).

Safety is paramount when operating electrical equipment out of doors, especially if there is a possibility of rain.

When using the small Actinic bulb traps, I find that placing a waterproof cover over the battery to be sufficient. This prevents water forming a bridge between the terminals and possibly creating a short circuit.

Harry Eales.

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