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Archive for June, 2012

Cleaning Camera Optics

Posted by Tom Benedict on 28/06/2012

I’m still prepping for my trip to Amsterdam for SPIE. Kindle batteries charged? Check! AA and AAA batteries for my KAP rig charged? Check! Camera batteries charged? Check! Camera optics? HOLY COW! What’s that on my lens?!

For a lot of reasons, it’s better to keep optics clean than to let them get dirty. First and foremost, clean optics perform better. There’s no sense dropping $2.5k on a lens if you’re going to let dirt stick around and degrade its performance. By the same token, there’s no reason to let a cheapo kit lens perform any worse if that’s all you’ve got. The cleaner your optics, the higher quality your photos. It’s that simple.

Another reason to keep your optics clean is that once dirt gets on a lens, it’s free to move around and do further damage. Modern optical coatings are actually quite hard. But sand, cinder dust, and other particulate contaminants can and will scratch them. Better to get them off before an inadvertent wipe with a cloth makes a permanent mark on your glass.

I’ve seen all kinds of stuff on the market for cleaning camera lenses and filters. My favorite is the one we use at work to clean our optics. These optics:

CFHT with Megacam

We have two cleaning methods we use:

Method #1 is to blow the optics off. We have cylinders of high purity nitrogen at our summit facility, so that’s what we use. But a good bulb blower would work just as well on camera optics. These are less than $20 at any camera supply shop. I got mine off of Amazon for about that much. And before you ask why we don’t use bulb blowers at work, keep in mind that some of our optics are large enough to fill a room. Using a bulb blower, it would take weeks to clean some of these things:


Method #2 is what we refer to as a “wet wash” – good ol’ lens tissue and methanol. Depending on the optic and the direction it faces (up or down) we may do wet washes once a month, once a year, or only when transmission tests indicate they’re dirty. On my personal camera, I like to do them any time I can see anything on my lens that isn’t glass.

But there’s a trick to it… As with most things, the success of a wet wash depends a lot on technique. Here’s how I do mine:

First, wear gloves. If you’re constantly re-depositing finger oils on your optics, all the cleaning in the world won’t mean a thing. Latex gloves degrade rapidly at 14,000′ of altitude because of the higher percentage of ozone in the air, so we use powderless nitrile gloves. At sea level, latex gloves should work just as well. Members of my family have latex allergies, so I use nitrile gloves at home, too. Any time you plan to touch optics, wear gloves.

Second, don’t touch the optics. Not with your gloved fingers, anyway. The only thing that should touch the glass is your lens tissue. And even then it should only touch glass when it’s got methanol on it. The gloves are there to keep your finger oils off of the lens tissue. Don’t let your fingers touch the glass.

I mentioned lens tissues. We use Berkshire Lensx 90 wipes. They’re 4″x7.75″ in size, and come in packs of 500 sheets. We use these universally, regardless of whether we’re cleaning an optic half an inch across, or one that’s three feet across. These are the lens tissues we use for everything. To use one, we pull a single wipe from the bag and fold it in half, rotating 90 degrees each fold, until we have a single folded edge about 1″ across. (We’ll fold one additional time if the optic is small.) At that point, the wipe is ready to use.

I also mentioned methanol. We use high purity stuff from a chemical supply house, but you can get it elsewhere. Some of the lens cleaners you can get at the camera store are actually straight methanol. You can also check with your local camera store to see if they have contact information for a supplier in town. Chances are they use methanol or ethanol in their repair shop. Whatever you do, don’t use rubbing alcohol from the pharmacy. Most of these are 70% alcohol, with the other 30% water. In the next paragraph I’ll describe why this is not what you want.

One important point with any alcohol: they are hydroscopic. That means they’ll suck water straight out of the air. Once an alcohol becomes hydrated, it is useless for cleaning optics. As you wipe across the glass, you’ll see microdroplets left behind the wipe. These are water drops that stick around after the alcohol has evaporated away. They can and will leave water spots on your glass. Once you get water spots on a coated optic, it’s practically impossible to remove them. Don’t let it happen! If you see droplets forming while you clean your glass, wipe them away and stop what you’re doing until you can replace your alcohol. I keep my methanol in a squeeze bottle. At the end of a cleaning session, I squeeze the excess air out of the bottle and flip the lid closed. This slows down the hydration process, but it can’t stop it. Check your alcohol before use and discard it once it becomes “wet”.

Back to the lens tissue!

To load a lens tissue with alcohol, you only want to wet the very edge of the folded tissue. Don’t saturate the whole thing. It’ll leave a wet trail of alcohol across your optic that will suck water out of the air and still leave microdroplets, even though your alcohol is “dry”. You only want enough methanol on the edge of the tissue to wet the edge. No more.

Once loaded, a tissue is good for one pass across the optic. One pass, then toss it. No matter how well you blow your optics off first, there will be microscopic dust particles on the glass that your lens tissue will remove. Once you lift the lens tissue off the glass, don’t let it touch the glass again or the dust it picked up will act as tiny abrasive particles that can scratch your glass. One pass, and toss it. Learn the rule and live by it.

When applying a lens tissue to an optic, use only light pressure on the tissue and move at a slow enough speed that you can barely see a band of alcohol film on the glass as it evaporates away. I try to keep the evaporating “tail” behind my wipe at only a millimeter or two of width. If it’s wider than that, I’m moving too fast. Narrower, and I’m probably moving too slow.

For an optic the size of a camera lens or filter, I’ll fold up a tissue, drop methanol onto it, and take a single swipe across the center of the optic. >toss< Then I’ll load another one and wipe a circle around the outer edge of the optic.>toss< Then I’ll take a good hard look at the optic before possibly applying a third on any remaining trouble areas. If the optic is clean, I’ll flip it over and repeat on the other side. Using this technique, you should be able to clean an entire camera bag of lenses in thirty minutes or less.

What about bigger optics? Take it in stripes. Here’s an example:

Big Focal Plane

This is one of our detectors at work. It’s 40 2048×4608 pixel CCDs arranged in a mosaic that’s roughly 300x350mm in size. I fold my lens tissue so it’s about 1.5x as wide as the narrow edge of one of these chips. My first “stripe” is from top to bottom along the leftmost edge of the frame, covering just those two chips. My second “stripe” is from top to bottom along the next line of chips. I get about a 50% overlap this way so I know I don’t have gaps. The stripes proceed this way from left to right, wiping from top to bottom. After each stripe the lens tissue goes on the floor and I fold a new one. By dropping the tissues on the floor I run no risk of accidentally touching one and contaminating my gloves. Once the entire surface has been cleaned in stripes, I’ll prep a tissue and wipe along each edge. (Yes, that’s 12 more tissues.) This catches any goop I might have bulldozed across the optic with one of my stripes. Once that’s done I’ll take a good close look. If it’s still dirty, I’ll repeat the entire process until it’s not. And before you ask, the 40 CCDs in this camera live inside a vacuum cryovessel. I don’t touch the chips themselves with this technique. What I’m cleaning is the optical window that lets light into the cryostat.

So I’m one step closer to being ready for my trip to Amsterdam. My camera, the one lens I’m taking, and all three of my filters are clean. Now where did I put those battery chargers?

– Tom

Posted in Engineering, Photography | 1 Comment »


Posted by Tom Benedict on 25/06/2012

This has nothing to do with machining or kites or photography or sailing or anything else I typically write about. But I had to share a realization I had earlier in the week:

Half-and-half is, to hot beverages, what ketchup is to food. No matter how gnarly that cup of coffee is, a dollop of half-and-half will make it taste like coffee-flavored half-and-half, which ain’t bad!

Not sure where that came from, but there you are.

– Tom


Posted in Uncategorized | 4 Comments »

Traveling KAP

Posted by Tom Benedict on 22/06/2012

I’m heading to Amsterdam in less than a week for the SPIE Astronomical Telescopes and Instrumentation conference. Most of my time will be spent at the conference, of course, and a good chunk of it will be spent walking around Amsterdam and taking in the sights. But at least some of that time will be spent with a kite winder in hand, doing aerial photography using a camera suspended from a kite line. For ground photography I’m bringing two cameras, a small tripod, and my carbon fiber pole. But what to bring for KAP?

The most versatile answer is, “All of it!” But that’s not the most practical approach since I’m already bringing posters for the conference, a laptop, clothes, etc. I can’t justify carrying that much stuff. Some of it will have to stay home.

Rather than pare down what I don’t think I’ll need, I’m starting over from scratch and only considering the stuff I do think I’ll need:

First and foremost, I have to choose kites. I have six kites I use for KAP, spanning the wind range from 4kt to 20kt+. But I’ve been assured high winds are rare in Amsterdam this time of year, and that 5-10kt is typical. So I’m only bringing two kites: my 6′ rokkaku and my 7.5′ rokkaku. Both of these break down to 35″ in length, and will fit inside my poster tube.

Next is winders: My main winder is a home-made plywood winder with 1000′ of #200 braided Dacron. It’s great for rapid release and retrieval, but it eats up more room in my bag than my laptop, power supply, mouse, and cables! It’s staying at home. Instead I’m bringing a hoop winder with 500′ of #150 braided Dacron. It’s slower to operate, but I use it enough for this to be an easy transition.

Next is the choice of camera and rig. I’m already planning to bring my Canon T2i for ground photography and my Canon A650 for pole photography (if I can manage to pack my photographer’s pole, that is!) I’ve used both of these cameras in the air, and have a rig for each. But they’re practically the same size. Rather than bring two rigs, I’m planning to bring the shutter cable for the A650 and use it on my T2i rig if I wind up going that route. It already has all the required mounting holes to take either camera.

As far as accessories go, I’m limiting myself to a hat, gloves, battery chargers, and a small kit of tools and parts for any reasonable rig repair I’m likely to face. The anemometer, strap, carabiners, additional kites, extra winders, night lights, and all the other gear I typically carry will stay at home.

Everything but the cameras and kites will go into my checked luggage with my clothes. I’ve had enough fun with airport security over the years that I don’t want to risk having to leave my winder or my KAP rig behind when I go through security. Sure, there’s a chance it might get lost or stolen. But there’s a rule I follow every time  I travel: never take something you can’t stand to lose. If my luggage is lost, it’ll be lame. But it won’t be the end of the world.

I’m really looking forward to this trip to Amsterdam. The SPIE conference happens once every two years, and is a prime opportunity to touch base with others in the field. Amsterdam is a city with a rich history I’ll only be able to scratch the surface of during my short time there, but already I have a list of places to visit. And every opportunity to do KAP off-island is a real treasure. It should be a fantastic trip.

Oh! And the poster? It finally came together:

SPIE 2012 Vacuum Poster

– Tom

Posted in Kite Aerial Photography | Leave a Comment »

My Favorite New Tool: West Marine Epoxy

Posted by Tom Benedict on 21/06/2012

When I started work on Smilodon, I knew I’d have to get a bunch of rigging, blocks, shackles, etc. After seeing the state of the hulls, I also knew I’d need to get epoxy, polyester, and gel-coat resins. I planned to use the epoxy as my mainstay fix-it resin, polyester as the primer layer prior to applying gel-coat, and gel-coat for the final surface coat. Rather than mess around, I splurged and picked up West Systems resin, hardener, and filler. It was expensive, and it irked me I had to buy pumps separately. But it’s proven stuff, so bought it anyway.

I wound up having to repair all manner of holes, dings, old screw holes, scratches, etc. By the time I was done I’d mixed dozens of cups of epoxy, run it neat, at ketchup consistency, at mayonnaise consistency, and I wound up mixing up one particularly stiff batch that was closer to putty. By the end, it had become my favorite new tool.

Last night I finished the work on the battens for the mainsail. For some reason the battens had been bolted into the main under far more tension than I like to run. I cut the bolts off, pulled the battens out, stuck Hobie batten tension caps on the luff end, and Tren-Tec leech caps on the leech end. Before inserting them into the sail, though. the Tren-Tec caps had to be glued on. They suggested using epoxy or silicone. Without any hesitation I went for the epoxy.

The session went something like this: Lay the battens on the table, pull the caps, wipe battens with alcohol, shoot alcohol into the caps. Dry thoroughly. Mix a cup of epoxy (one squirt off each pump – perfect ratio every time!) Wet the batten tips with neat epoxy. Mix in some colloidal silica filler to a consistency between ketchup and mayo, and load it into a syringe. Shoot the caps full of epoxy and squooge them onto the tips of the battens. Wipe excess, line up, and set aside to set.

This took me all of fifteen or twenty minutes, tops. When I checked the caps this morning, the epoxy was hard as a rock. Still, I’m giving it the full 24 hours to cure. Now my leech caps are a permanent part of the battens. Done.

Over the years I’ve used a variety of epoxies I bought from the hardware stores. Tubes go bad, resin gets compromised, and mixing ratios are always approximate. Never again! I’ve got all my West Systems stuff on one shelf in my cabinet, so using it is no more difficult than pulling a screwdriver out of a drawer.

Love it.


Posted in Engineering, Sailing | Leave a Comment »

Man Overboard!

Posted by Tom Benedict on 19/06/2012

Work has been utter hell. Twelve-plus hour days are getting to be common, and six and seven day work weeks are becoming the new norm. We’re all ready for things to get back to normal. And we’re all making the most of the time off we do get. I missed a holiday last Monday, and I was at the summit from 7am to about 9pm Saturday. Sunday was my one day off. So I made the most of it.


We took Smilodon, our rebuilt Pacific Catamaran, out for the morning. Winds were light, but enough to make for good sailing. Because of work I haven’t had a chance to do any work on the mainsail battens, but otherwise the boat is really starting to shape up. I wanted to see how far we could go in a reasonable amount of time, but back in the back of my mind what I really wanted to do was some man-overboard (MOB) drills.

I believe in MOB drills the same way I believe every new driver should skid their car, just to know what it feels like. Think of it this way: If you spend a couple of hours skidding your car intentionally and learning how not to panic and how to get your car back under control, when it happens on the road your chances of survival are considerably higher. The same is true of MOB drills: If the first time you do a MOB drill is when someone actually falls off the boat, your chances of knowing what to do are slim. But if you practice it regularly, it’s almost a non-event.

There’s another benefit to MOB drills: If the people you sail with know with certainty that you can turn around and pick them up in under two minutes, they’re a lot less likely to panic if they wind up going overboard.

Besides, MOB drills are fun!

I wasn’t quite sure we were all ready for MOB drills, but I at least wanted to try with an inanimate object. So I brought along an empty milk jug. Fill it halfway with water, and it makes a pretty good simulated MOB. But before I could even think about pulling it out, my son pointed to starboard and said, “Is that trash?” I looked where he was pointing, and saw a bait bucket floating on the water. MOB DRILL!

I had to tack twice to reach the bait bucket, but we got it on the first pass. Once everyone saw how smoothly that went, it was like a dam breaking. First Rydra and our son went over the side. Rydra grabbed a camera, and took pictures as we sped off into the distance:


And as we came back around to “rescue” them:


After my daughters and I came around and “saved” them, they went in the drink for their own turn at sea.  By the end of the day we’d run two live MOB drills, and one more dry run when Rydra’s hat fell off. I only missed my first approach once, when my two daughters were in the water. I made my turn too soon, and didn’t have the sea room to finish the tack and come back for them. But the second pass went like clockwork.

The P-Cat is significantly heavier than the Prindle 16 Rydra and I used to sail. The P-16 could literally turn on a dime, but the P-Cat needs a little more room. It also has a lot more momentum because of the added weight, so it won’t stop as quickly as the P-16. Still, once I got the hang of it, I found it to be just as maneuverable

We sailed as far south as Puako. By the time we turned back, the wind had dropped to a gentle breeze. We were cutting across the swell, which made for a slow roller-coaster of a ride. But the water was smooth and the reefs, only thirty feet below us, were gorgeous. I had to skipper the boat, but the kids knew just how to enjoy the view.


The experience of the MOB drills helped when it came time to sail back into the harbor. I didn’t mess around with dropping the main early and sailing back under jib alone. We came in under full sail, made our turn into the wind, and Rydra and the girls jumped into the water while my son and I furled the jib and dropped the main. Less than a minute after we’d cleared the harbor wall, we were nose to wind with no sail set. Perfect!

There’s still one big step left before I’m 100% confident in boat and crew: I need to fall overboard, and they have to come back and get me. Until that happens, I’m leery about doing anything that puts me in a position where I might go in.

To date I have only unintentionally gone overboard on a boat twice. The first time was when I was struck by the boom during an unintentional jibe on our P-16. The second was when I was hiked out on a wire, and my trapeze line failed. Dodging the boom became second nature after a while, and the boom on the P-Cat is more than a foot higher than the Prindle 16. But equipment failure can and does happen. That trapeze wire worries me. At the moment I’m the only one with a trapeze harness. But until my crew can come around and rescue me from the water, I have no business hiking out on a wire. If the wire breaks or a knot fails, I’m in the water with no assurance anyone will come back to get me.

So, of course, this is top of the list for the next time we head out. Someone else will skipper the boat, and I get to be the man overboard. It also means I get to play around with cameras! So next time I hope to come back with more pictures of our P-Cat, the beautiful waters of Hawaii, and anything else we encounter along the way.

– Tom

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On The Water and In The Air

Posted by Tom Benedict on 12/06/2012

Two big landmark events happened last weekend: we got the boat out on the water, and I had my turn with the World-Wide KAP Banner.

Sailing was… Well… You know that song, “Feels Like The First Time” by Foreigner? Yeah, it felt like the first time. Felt like the very first time. In case anyone thinks this means it was wonderful, passionate, and opened new vistas to us, you missed the point: It was awkward, bumbling, kinda messy, full of mistakes, but we all came away smiling.

In a place where the wind never truly dies, you can only go so far rigging a boat in the yard. A bunch of little stuff still needed to be done when we rigged the boat at the harbor. It took us two hours and involved more than a few mistakes. But finally we were ready to put in. I’d forgotten how easy it is to control the power on a cat, so we tried sailing out of the harbor with only the jib. We also completely forgot to put the daggerboards down. The result? We almost side-slipped into the harbor wall! Eventually we sorted it out.

Once the main was up and the boards were down, we found the boat pointed well. We were able to point 45 degrees to the wind and still make good headway. The helm balance was almost perfect, with just a slight bit of weather helm. The jib furler worked perfectly, and the main halyard winch worked well enough for the purpose. Our tacks were anything but picture-perfect, but eventually we made it out of the harbor and sailed as far south as the Mauna Kea Resort. Rydra asked that we turn around at that point, so we tacked back and headed home.

We weren’t done with the mistakes, unfortunately. Despite blowing every tack and having overwhelming evidence that we could bring the boat to a standstill at will, I was concerned about sailing into the harbor under full sail. So we lowered the main and tried to sail in with just the jib. This time we missed the harbor completely and almost hit the harbor wall. I had to jump overboard and swim/tow the boat away from a bunch of fishermen who were more than surprised to see our ineptitude. (At least they got a good laugh out of it!)

Eventually I put the main back up and we sailed in as the last of the wind died. We hosed everything down, packed everything up, and headed home alive, mostly injury-free, and smiling. Oh! And alive! Did I mention that? That’s a good thing.

We’ve got some tweaks we’re going to make before taking it out again. The battens on the main are an over-tensioned mess, I want to add stirrup ropes for climbing into the boat, and we need to come up with a better way to stow our lunch so it doesn’t get soaked. But these are minor tweaks. We’re good to go for next weekend.

And no, I took not one picture. Not. One. We were so busy sailing, the camera never came out of its case. Ah well. Next time.

The other big event was the World-Wide KAP Banner. There’s a story to this one:

Some years ago, a fellow KAPer named Ramiro Priegue came up with the neat idea of making a banner and sending it around the world to anyone who does KAP. As each KAPer received the banner, they were to sign it, take it out, photograph it from the air using a kite-lofted camera, and then pack it up and ship it to the next person on the list. His idea was warmly received, and shortly afterward the World-Wide KAP Project was born. The banner was made, and the first photograph was taken. Since then it has traveled all over the place. The banner is covered with signatures from KAPers from the far corners of the globe. It’s a piece of kiting and KAP history.

But where to photograph it? I thought about all the places I’ve flown on the island, and finally decided to take it to Anaehoomalu Bay. This is where I took my first really photogenic picture from a kite. It’s where I went when I switched from my first KAP camera, a Nikon Coolpix, to my second, a Canon Powershot. It’s where I got my kite stuck in a tree for the first time. It’s where I crashed my first rig. In a way it’s a part of my own KAP history. Plus, it’s gorgeous there.

I walked out to a spot where an old marine diesel had washed ashore ages ago. The engine is rusty to the point of being mummified. The thing is so old, it shows up in maps of the area. It’s one of my favorite KAP subjects. I pulled the banner from its bag and laid it out in the sand next to the engine. It was great seeing all the signatures everyone had put on the banner. There was artwork, logos, cartoons, names, stories, all kinds of things. I wanted to stop and look at them all, but I only had a short time to photograph the banner. I found myself wishing I could take a picture so I could read them all at my leisure. Then I had to laugh: That’s exactly what I was doing!

So without further ado, the banner for the World-Wide KAP Project at Anaehoomalu Bay, on the Big Island of Hawaii:

WWKB and Diesel

WWKB Hawaii

Posing with WWKB

WWKB Anaehoomalu Bay Vertical Panorama

Clear skies and fair winds.

– Tom

Posted in Kite, Kite Aerial Photography, Sailing | Leave a Comment »

Kudos to Sailcare!

Posted by Tom Benedict on 06/06/2012

Our jib came back from Sailcare today. OH MAN!

Several times already in the restoration of Smilodon, Sailcare came to the rescue. The pecuilar combination of sheave and cam cleat that’s used on the jib sheets of the P-Cat? Sailcare had them when no one else did. Affordable fully adjustable trapeze sets? Sailcare again. And now our sail…

I knew Sailcare did more than just stitching. They do a very comprehensive sail cleaning procedure called the LeMauney process. Sure. Whatever. I just needed the holes patched and the zipper sewed on properly. But why not get it cleaned while it’s there? Can’t hurt, can it?


Our jib came back looking practically new. Ok, ok, when I laid it on the floor and looked at the color of the cloth I could see it was still somewhat yellowed. But it was nothing nearly as bad as it had been. The stains? Gone. The dirt? Gone. The mouse droppings (I kid you not… I had some surprises when I pulled the old zipper off!) Gone. The corrosion build-up on the grommets at tack and clew? Gone! And the cloth itself feels fantastic. (The LeMauney process re-impregnates the cloth with resin.) This sail is at least twenty years old. There’s a good chance it’s older than I am. Now it doesn’t even look like it’s been used on the water.

I almost felt bad re-attaching the jib blocks. The line between the jib’s clew and the blocks isn’t the cleanest in the world. And now it shows! I may take them back off and wash that line before putting it back on.

I unpacked and re-packed our gear bag to be certain I had everything in it and we were good to go for the weekend. We’re ready for the water. The kids are starting the summer as landlubbers. By summer’s end they’ll be sailors!

When we do finally tear things down to re-do the decks, I’m planning to pull the battens out of our main and send it off to Sailcare to get the same treatment our jib got. It’s a little softer than the jib, so I don’t know what they’ll be able to do for it. But I’m looking forward to finding out.

– Tom


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Sailing Soon and SPIE Posters

Posted by Tom Benedict on 01/06/2012

Good news! Sailcare sent word that our jib is in the mail. Now the only question is when it’ll show up. I’m guessing at some time next week, so next weekend we should be on the water. Today I went through the list of things left to do on the boat and started hammering out the last of the little things. County-issued VIN sticker on our trailer? check! Public boat ramp fee stickers? Check! Verified daggerboards can be inserted the full length of the trunk? Er… not checked… But by the end of the weekend, the only thing left should be to put new telltales on the jib.

Meanwhile I’m getting ready for the SPIE Astronomical Instrumentation 2012 conference, which starts in Amsterdam a month from Monday. Manuscripts are due by the 6th, and mine is almost done. I got the last of the figures in this afternoon and sent it out for edits. The only other task left after the paper is to put the poster together. Technically I can finish the poster the day of my poster session, so long as I get it printed in time. That seems needlessly risky to me, though. I’m planning to print it before I leave and take it with me on the plane.

I like making posters. I don’t mind public speaking, even though I get terrible stage fright. But putting together a talk isn’t nearly as fun, to me, as putting together a poster. I don’t really like the traditional academic or engineering poster formats, so I take posters as a chance to have fun with graphic design. I look at it this way: The whole point of a poster at a poster session is to grab the eye, make it easy for a bystander to get the gist of what you’re saying, and give them enough information to ask you at least one decent question. You don’t need to reproduce the entire contents of your paper on your poster! In short what you need is eye candy.

This is my poster from SPIE 2010:

SPIE 2010 - Espadons PCC Poster

Not your typical conference poster. But hey, it was a lot of fun to make! And if you look at it, the bulk of the information from the paper is in it in visual form. It does its job.

The poster for SPIE 2012 will be more of a challenge. The paper discusses some of the unexpected consequences we ran into from our conversion from liquid nitrogen cooling to closed-cycle cooling (the topic of the poster shown, above). So there’s no clear road map on this one. It’s a scattered collection of problems, investigations, findings, and revelations we had along the way. In the end we got a new set of guidelines for good practices when designing closed-cycle cooled cryostats. But presenting it that way misses the real thrust of the paper: that we were clueless when we started.

“Clueless”. Actually, that’s inaccurate. We had clues. What we didn’t have was answers.

And that’s how I’d like to present it: as a whodunnit. Troubleshooting doesn’t follow a logical progression from A to B to C. It’s closer to a murder mystery, where the intrepid detective gathers clues, interrogates witnesses, forms a hypothesis, and eventually builds a case. This paper, and the associated poster, is really targeted at the troubleshooter rather than the instrument designer. It’s one thing to say, “Unless a cryostat is cooled below 77 Kelvin, the getter will be unable to pump nitrogen, and some other mechanism must be employed.” It’s another to say, “When we switched vacuum gauges, all of a sudden our cryostat couldn’t hold vacuum! It’s like we’d introduced some sort of leak into the system. But we never found anything with a leak check, and our RGA showed no uncharacteristic abundances. What was going on?!” A troubleshooter might read the first sentence and not see how it relates to a problem they’re having. But that same troubleshooter might read the second and say, “Hey! That’s just like my cryostat! How’d they solve this?!” Just like a murder mystery, the whole idea with a poster is to hook the reader (or viewer, in the case of the poster.) Everybody loves a good whodunnit.

Now I just have to figure out how to do that with a poster…

– Tom

Posted in Engineering, Sailing | 1 Comment »