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Mercury vapor black light set-up

Mercury vapor black light set-up
Santa Fe Nat’l Forest, Santa Fe County, New Mexico, USA
May 31, 2014
Size: 400 W
Download high resolution image here.

This set-up is shown as fielded at 9200 ft, National Forest Road 412 near the Aspen Ranch Trailhead #9 of Rio en Medio Trail #163, Santa Fe National Forest, Aspen Basin 7.5’ quadrangle, Santa Fe Co., NM (35°47'53.6"N 105°49'59.6"W). It was inspired by those used at the 2013 Bugguide gathering in Arizona. I alternate between using a clear mercury vapor 400 W bulb and an American DJ E40 400W Elliptical Blacklight. I have not determined which attracts more bugs yet.

The bulb screws into a Day-Brite Lighting HBO400MMT metal halide high-bay ceiling ballast. Though designed for metal halide bulbs in common use today, such ballasts are backward compatible with the older mercury vapor lamps. The latter should be used to attract bugs, since they produce more near UV light. The black light version uses a bulb which filters out most light other than UV. This ballast is ideal for field use because it is rated for damp environments. The 3/4" NPT internally threaded cast aluminum hub (from which the ballast normally hangs) is modified to mount onto a Sokkisha surveryor's tripod, as shown. For this, the hub's outer flange is turned down to fit into the 2.6" diameter tripod base plate hole, and a threaded insert screwed into the hub's center (fashioned from a 3/4" NPT brass plug) receives the tripod's 5/8" x 11 tpi mounting screw. Additional modifications to the ballast are aluminum lifting handles attached to the reflector mounting bracket, and a 115 VAC panel mount inlet power plug socket installed on the wiring access cover plate. The unit is powered by a portable gasoline generator from Harbor Freight.


I've added an Appleton VPGL4HR heat resistant glass cover to the lamp, as shown in the 3'rd image. I was able to find one on eBay for a good price. It's designed for such a bulb, but not the ballast itself. So, I machined an aluminum adapter for it on a lathe. The adapter includes a 7.5 inch diameter, 4 threads per inch thread matching the one cast into the glass. There is a silicone rubber gasket that the cover seals to when screwed in. The reasons I find the cover desirable are that the bulb itself is fragile, it is hot enough to burn skin in use, it kills thousands of small insects that come into contact with it overnight, would likely shatter if it got rained on, and, since it diffuses light, it is less harmful to the eyes. A less concentrated spot of light focuses on the retina with such a diffuser. I always wear clear UV-blocking goggles too when it is on.

The 4'th image shows the upgraded lamp as fielded with the clear bulb (visible light) option on 01 JUL 2016 in Coconino Nat'l Forest at the north end of FR 131 at the Parsons Trail (144) head, Sycamore Cyn. Wilderness, Clarkdale 7.5' quadrangle, Yavapai County, Arizona. Note, too, that I have replaced the clothes line strung between two trees to support the sheet with a Craftgard Portable Quilt Display Stand (in case suitable trees are not available). Though difficult to see in even the high resolution download, staked guy-ropes on each vertical pole are used to prevent the stand from blowing over.

The 5'th image shows the set-up as fielded on 16 AUG 2019 along State Rt. 61 (FR 150) about 1.5 miles north of Wall Lake in Gila Nat'l Forest, Catron Co. NM. Trees were available to support the clothes line this time, so the quilt stand was not necessary. I replaced the cheap Harbor Freight generator with a much more reliable (and expensive) Honda EU2200i after going through two of the former. I also added a Black light trap from Bioquip. A few species were trapped that I did not find on the sheet that night, but it is of value primarily if you leave the set-up unattended for long periods.

The 6'th image shows the set-up as fielded on 22 JUL 2022 in the parking lot overlooking Higgins Canyon in the Sabinoso Wilderness, San Miguel Co, NM. This version of the sheet includes a sleeve on top fitting the support rod, and utility cord tension lines passing through aluminum grommets around the sides and bottom. Securing the sheet in this way virtually eliminates flapping in the wind. The sheet still billows in the wind, but the lines do not have to be very tight to stabilize the rapid flapping that can occur if the edges are free. The billowing itself varies slowly enough to permit focusing a camera onto subjects clinging to the sheet. The sheet has been replaced from the previous version (cotton with 80 by 100 threads per inch) with one made from a polyester table cloth with 14 by 20 threads per cm. The grommet holes are made by melting through the sheet with a soldering iron. This produces a solid polyester ring that the grommet can be securely punched onto.

Insects photographed from field trips the lamp has been used on:

Aspen Ranch 2014-05-31, Santa Fe Co., NM (35°47'53.6"N 105°49'59.6"W)

Aspen Ranch 2014-08-31, Santa Fe Co., NM (35°47'53.6"N 105°49'59.6"W)

Turkey Canyon 2015-08-05, Eddy Co., NM (32°11'05.2"N 104°41'34.3"W)

Parsons Trail head 2016-07-01, Yavapai Co, AZ (34°51'51.5"N 112°04'18.0"W)

Woodard Ridge 2017-05-27, Sandoval Co., NM (35°48'09"N 106°30'04"W)

North of Wall Lake, 2019-08-16, Catron Co., NM (33°22'01.3N 108°04'23.4"W)

Spruce Loop, 2020-09-05, Sandoval Co., NM (35°48'49.0"N 106°40'58.0"W)

Sabinoso Wilderness 2022-07-22, San Miguel Co., NM (35°35'34.5"N 104°36'58.8"W)

Images of this individual: tag all
Mercury vapor black light set-up Mercury vapor black light on tripod Mercury vapor black light on tripod, updated with glass cover Upgraded set-up, as fielded in Coconino Nat'l Forest Set-up fielded north of Wall Lake Set-up fielded in Sabinoso Wilderness parking lot

Nice set up
I still like mine because the of bug-lovers crowds milling around cannot topple it over. Your tripod is nearly as big as my whole frame set up!
I'm missing a ground sheet for walk-ups in you photo

Ground cloth and tripod
I forgot the ground cloth. I'll put one down next time. A big mole showed up and got all the bugs on the ground this time.

The standard surveyor's tripod used is the minimum weight needed to support the ballast high up safely. The legs unfold and telescope out quickly, and the ballast screws on by hand. Its pointed feet are designed to be pushed into the ground by the heal of your foot, so it's quite stable.

Dear Edward, What a wonderful sharing!!!! I am keeping a reference to your photo for when I get more advanced. I have been struggling with setting up portable black light rigs and used mine for the first time a week agao. They are GREAT and I have already established that it is worth the effort to set up a second sheet even thought the sheets are not more than 1/2 mile apart. I am using deer feeder batteries now so will have to step up my act in the future and YOU have given me the tools! Many thanks!

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