Insulated DIY Dew Shield for Telescope v1.3

(Click on any image to enlarge.)

I live in the temperate rain forest of coastal Oregon. Dew is a big problem. This doesn't make me an expert on dew, it just gives me more incentive to try to make a better dew shield. Honestly, I haven't had the opportunity to try this design out, but I thought it promising enough to share as is. The idea was to create a lightweight insulated tube with a protective outer shell and a light absorbing cloth or felt interior. My design uses high density polyethylene (HDPE) for the outer shell ($7.95 for a 2'x 3' sheet at Tap Plastics); fleece for the interior fabric ($4/yard or less); a can of expanding insulating spray foam ($7). The total material cost for my 6" scope was about $20, weighs in at about a pound and should have an R=value of around 2.

UPDATE: 12-24.2012:  I took the scope outside at 6:00 pm.  Interior temp: 68 F; Exterior 47F with 80% humidity. The only thing that was visible was the moon and it mostly a glowing disc behind Earth's clouds.  3 hours later the outside of the shield is damp, but inside clear as a bell.  Not the worst dew I've encountered, but a pretty good indication that the basic design is sound.

 STEP 1: Frame

You will need a frame or scaffold to support the inner wall. I conveniently had four. 1/2" threaded rods, but wood dowels or something else would do as well.
The rods are located so that their outer edge is tangent to what will be the inner diameter of the dew shield.
Four supports seemed enough for a 6" tube. More would probably be needed for larger diameters .
The length of the frame should be generously bigger than the length of the tube you are making. In this example I am making a 16" long tube 4-1/2" of which will be on the optical tube leaving 11-1/2" in front of the scope. The rule of thumb, I gather, is 1.5 times the diameter. So this design is nearly 2x.

STEP 2: Inner Form

I used part of my sheet of HDPE to  make the inner form.  This part stays in only until the foam hardens, then it is removed.  Other things could be used; a cardboard tube of the right diameter or sheet metal, etc.

Here I've simply stapled the inner tube in place.

Step 3: The Liner

I chose fleece for 3 reasons:

1.  I thought its many fibers would be good light absorbers.
2. The fabric is resilient, workable and cheap.
3. It is itself an insulator.

I understand that felt is often used and this method does nor preclude that.

Whatever material you choose fit it tight around the inner barrel BUT DO NOT ATTACH IT TO ANY PART OF THE INNER BARREL. Recall that the inner sleeve will be removed.

 STEP 4: Spacers

Attach spacers the height of the foam insulation  (how thick your dew shield will be).  Some sites show spray in foam with an R-value of R4/inch.
In this example I'm using approximately 1/2" spacers for a value of  R2
Glue the spacers on in a staggered pattern.

  

STEP 5: Outer wall

Secure the outer wall tight against the spacers.  I tried  gluing it, but eventually added 3 rivets.  One could also simply duct tape it.
Tape the cloth ends to protect them and keep them out of the way.

STEP 6: Foam

Stick the expanding foam straw in all way and pull the trigger and pull the straw back foam almost all the way to the edge.  Repeat around both ends of the tube

STEP  7: Curing

Because the foam is sandwiched between HDPE it may take a day for the center to cure while the ends will be done in an hour.  Don't be fooled;  let it cure.

 

STEP 8: Remove the inner liner

One you are sure the foam is  sufficiently cued, take the tube off the scaffolding and push the inner sleeve out.

Removing the inner tube will also expose the central area to more air enabling final curing and more importantly, its final weight.

STEP 9: Trial Fit

Pull the fleece back over the outside.  Test fit it on your scope.  One end my work better than the other.
If the fit is to tight you can compress the foam and/or remove some of it.
If the fit is too loose you can pull back the fabric from the foam at one end and layer is some additional fabric to reduce the diameter.

In fact this second method could be used to create tubes of larger inner diameters to support longer lengths or cure  vignetting issues.

STEP 10:  Finishing

Trim the excess fabric back and then stretch and tape it to the barrel.  Most people will be able to achieve superior aesthetic results.

STEP 11: Cut outs and other features (Optional)

As you can see in the photo I had to cut out a notch for my Celestron tube mount.  One can imagine fitting more elaborate mounts and/or fittings into the design before foaming.  These are left as an exercise for the reader.

Poker Chip Rack

The Search is Over

I finally got some time to polish off the Navy search light I've been "restovating." I had completed the shutter and tested the lamp, but the shutter let too much light through. I fixed that by adding a narrow piece of extruded aluminum to each shutter. This had several laudable effects:

• It's more like the original shutter design. 
• As the photo below shows, light leakage is minimal.
• The finished edge of the shutter looks better, 
• The added mass smooths out the operation.

 


A few other details had  to be attended to, like installing a handle and figuring out and recreating  the return spring.

Tansu

A tansu was not our first thought for a solution to our kitchen storage needs.  We have a small kitchen (the standard 10x10), naturally, as Americans, we need more room for our stuff. We looked at many different hutch designs and found them to be expensive and many too big for our space.  We both admire and respect Japanese design; the frugality, simplicity and modesty of it.  Perhaps you've seen a Japanese tansu in the form shown above or as "step cabinets."  Either way, you've probably remarked, "I'd love one, but they are so, well, 'Japanese.'"  Tansu purchased we did; confident that tansu transformation could we effect.   We bought it from Shogun's Gallery in Portland.  They described it as about a one hundred year-old  "mizuya dansu" or kitchen cabinet.  Constructed of a kind of Japanese cedar, it is very lightweight at perhaps 30 pounds for the upper and lower parts combined.  It measures 15" deep, 36" wide and 68" tall.  Here's how we Americanized it. To make it into a hutch, two pieces were added: A matched back portion for the bottom half and An extension to the top part. Fortunately I happened to have some 50 year-old cedar barn wood that is a close match in grain and color to the Japanese cedar. Unfortunately I did not have enough of it, but the newer cedar will darken with age. We debated a long time over the counter top material and we finally settled on black granite which we purchase from Alpha Stone Works. Both units were securely screwed to their newer parts and those  parts then attached to the wall.  Thus the granite "floats" sandwiched between the two halves. I'm most pleased with the spice rack on two counts.  I made it at another location and when I brought back it slid right in like a part of the Space Shuttle.  Second, the full extension slider mechanism is completely hidden.

The Daily Grind(er)

The grinder design I showed 2 days ago didn't work out too well.  The path from the grinding mill exit to the removable cup with the grounds proved to be not steep enough.

Here's version II.  It works much better.

The cup easily holds the full capacity of the grinder.

As you can see, after investigation I found that the mill section could be of a smaller diameter.  Thus it's even easier to hold.  By making the "cup" for the grounds in a direct line and the same diameter as the mill exit the solution is far superior to the "square drawer" of conventional grinder designs.  They tend to leave coffee grounds on the drawer edge and the round shape makes it easier to pour into the usually round coffee maker.

This unit is made of 4 cedar parts.  All made with hole saws, but it could easily be turned from a single block on lathe.

Coffee Grinder

I've always wondered why coffee grinders were square. Round would be easier to grip, truthful in form to its rotating parts and just overall better looking. So today I made one out of scraps of walnut.

The conventional one at right from which I scavenged the parts.

The construction uses a 4" and 3" hole saw and then the parts are glued together.

Oh, and they aren't round because it's a heck of a lot easier to make a square one.

Lighting Lorcini

Since I was 7 years old this 1965 wall sculpture, "BETA BYG" by Gino Lorcini has been prominently displayed in my parent's home.  For perhaps the past decade, my father has asked me if it would be possible to illuminate it. I demurred each time, until my parent's most recent move which would have the piece in storage for a couple of years.  This combined with my guess that the technology was sufficiently advanced to make it possible at an economical price finally convinced me to try it.

The piece as seen in my parent's house (left) and back illuminated (right).  To see how the illumination works, click here for a slide show.

I consider this a first approximation of how this could work and the result merely a working protoype. Here's  why.


Design Goals

1. Illuminate the art from behind and sufficiently to be viewed in a lighted room.
2. Maintain the free-floating appearance on the wall.

Solution

From the beginning I thought the unit would have to be able to run on batteries so that an elctrical cord wouldn't spoil the effect of the sculpture floating on the wall.  This meant using LEDs as the light source, but I was unfamiliar with the options available.

The piece is about 13-inches square.  No prefab LED panel was available, and I wasn't going to spring for a custom one just for testing.  I tried a set of edge lighting LEDs from Luminedge.  The LEDs were certainly bright enough, but when I tried to attach them directly to the artworks white acrylic square the white proved too opaque and in any case, probably wouldn't cause enough of the light to diffuse forward and do so uniformly.

Aware that this is exactly the problem solved in LCD monitors, I bought a used one at Goodwill for $15.  I disassembled it and removed the sophisticated optics system for redirecting and diffusing the edge lighting.  I replaced the fluorescent tubes with the LEDs from Luminedge and cut the acrylic panel to slightly smaller than the art.  I didn't use all the sheets of optical paper used in the LCD. for one thing, there is a larger gap (about 3/4") between the art and the illuminated panel, afforded by the stand-offs, to allow the light to diffuse.

The effect was immediately satisfying.

The next challenge was where to put the batteries.  I initially mocked up putting them on the frame's edge, but decided against it due to my negative perception of the appearance it had on the frame.  I now think it is a better approach.

I then concluded that the batteries could go between the stand-offs and thus the custom battery case shown.  It is not as easy as it looks to make one, let alone one that works well.

The problem of getting power to the panel from the pack proved difficult.    For obvious reasons I didn't think a plug-in solution would work.

Once I had the illumination working I tested the run-time on batteries; about 12 hours was possible.  I concluded a timing circuit would be necessary to ensure the illumination would not be left on.  After evaluating a few I settled on a small, one hour timer circuit kit from Vellerman (K2579).
Even this kits diminutive size proved too much to place elegantly without increasing the depth.  Reluctantly I located it on the back, adding perhaps a half inch of depth and even that required relocating the circuit's largest component (the relay) off-board.
Issues With This Design

1. The battery pack requires a lot of handling of the art to change the batteries.
2. The battery pack casts a shadow on the unlighted sides.
3. The switches cast a shadow,
4. The depth is too great due to the timing circuit.
5. The timer always functions (no "always on") and always for one hour.

 Version 2.0 should address these shortcomings, but for now I'm just enjoying this new, illuminating view. 

Much To Do About Nothing

One Minute Case Studies presents the story of why the more you do, the more there is to do.

Toolbox No. 4 : Bicycle Tools

I was just about to sell my bike tools when I rediscovered bicycling.  To celebrate I cleaned off my tools and gave them a new home.

Each of my toolboxes has started from a central idea.  This one was to provide customized storage for the specialized, skinny, Park tools.  To this end, the lower tool drawer has 1/8th" slats that these tools nest between

Some features of interest.  I have a couple of 1/4" socket sets, but I could never for the life of me imagine what one would use a 4mm socket for.  Now I know; they make great drawer pulls.

An old handlebar was used for the handle.

The visible wood is maple, but pine, fir and plywood were also used.   What ever scrap was around.  The upper tray dividers are of cedar.

Bench Test

Alice had been looking for a particular piece of furniture for office. Ideally it had to be: 1 foot tall, to clear the glass partition to her neighbors cube; 3 feet wide, to span the opening; and 9" deep to accommodate plants. She had seen a couple of Asian designs that she liked, but they either weren't quite right or expensive and mostly both. We liked the design of this little stool, but it was obviously not wide enough.  I had Alice snap this picture and committed to building one based on its characteristics..

Accused of having a tendency to repair things too well (i.e. taking the quirkiness and "character" out of them  in the process of making them function better), I thought this might be a chance to prove I was capable of building something without sanding the history out of it.

I have had a bread board, which I believe I purchased between plays while antiquing with my mother at Niagra-on-the-Lake decades ago.   It measured a bit less than the requisite 3 feet, but the main surface was cracked in the middle and at 75 or more years oldit had plenty of character.

So here it is.  It used up almost all the wood and the only other material was for the drawer.

And here it is in Alice's office.  

SONY NEX OVERHEATING: Final Test Results

SUMMARY

After numerous tests and re-tests my conclusions are the following:

• There are ways (some more obtrusive than others) to lower the surface temperature of my NEX.
• None of these methods individually or taken together modify the following, essential characteristic of the NEX:
• From cold the camera will heat up, display the thermal warning, and then may or may not make it to the 30 minute mark (at which point the camera reaches its maximum 30 minute segment record time.).
• If the camera records to the 30 minute mark, then trying to record again immediately will result in thermal shutdown after a few minutes.
• If in either case, if one allows the camera to cool for 4 to 5 minutes, then the camera may record one or two more additional 30 minute segments (allowing for cool down in between), most often  without any warnings, even though the recorded surface temperature is well above the point where shutdown previously occurred. 

The best strategies for increasing the chances of making it to the initial 30 minute mark are, in order of effectiveness:

• Use the Sony 32 GB Memory Stick PRO-HG Duo Media 
• Use the AC adapter instead of the battery.

The following offer only marginally small improvements to cooling and/or record time.

• Keep the LCD open and use a small, portable fan.
• Remove the rear label and apply heat sinks and use a fan.

WHAT'S WRONG WITH THIS PICTURE?

Yes it's true that the NEX is sold as a still camera, and what a great still camera it is.  And yes it's true that  one might regard the video functions as a kind of "bonus" feature that is a "nice to have," but not worth too much time and attention if they don't work exactly as expected.    Although I do not agree with these assertions, even if I did, I would still find fault with my camera as is.  Here's why.

The behavior of the camera is paradoxical.  

1. Why does it report thermal distress at temperatures that seem far below temperatures at which it will later operate with out a fuss?
2. Why does it not report thermal distress prior to shutdown at higher temperatures?
3. Why does the camera's surface temperature continuously rise in spite of serious counter-measures?
4. Why does using the Memory Stick format seem to reduce the operating temperature?

It seems to me that even if the essential characteristics of the camera cannot be altered, some practical changes would make the camera more usable:

1. Determine if the thermal distress indicator is functioning correctly.  
2. Ensure the thermal distress indicator functions consistently.
3. Determine if the camera triggers thermal shutdown appropriately.
4. Provide guidance on maximizing record time (Examples: Memory Stick, AC adapter, waiting periods between recordings).
5. Add a countdown timer to recording (from 30 minutes) so that users know that there  is a maximum record time independent of card size.

Improvement on theses items would make camera operation more predicable and the user experience more enjoyable.

IT IS TIME TO ASK SONY

It's  time for Sony to acknowledge this as an issue and work toward a solution.  I intend to send these comments to Sony in a letter.  I urge others to do the same or to simply file a question with Sony customer support 

Some have speculated that the camera heats up more when recording using a fully charged battery.  My tests indicate that this is not the case.  My tests on my camera show that the heating curve depends more on the state of the camera (cold or warm) than on the state of the battery.

SONY NEX OVERHEATING: Final Tests

I've collected more data than is shown here, but this sort of sums it up.  For analysis see my follow-up posting.

SD VERSUS MEMORY STICK &
BATTERY VERSUS AC

Click on image to enlarge.

Basically this graph shows that my NEX-5N runs cooler on AC and on Sony's best 32 GB memory stick.  Even so, the effect on continuous recording time is small.


TRYING VARIOUS TECHNIQUES TO REDUCE TEMPERATURE

I separated out this chart to enlarge it.  All the effects on surface temperature are quite small and can only be seen when zoomed in.

Heat sink refers to the arrangement pictured here.  The back label is removed, replaced by the thickest 3M thermal PSA AVAILABLE and topped with two heat sinks that cover the entire area under the LCD.

Click to enlarge

This graph shows that even the most drastic approach results in only small and temporary temperature reductions.  On the Sony support forums it is suggested to turn "Steady Shot" off.  In my testing on my camera this too made little or no difference.

Indeed, the only way that I was able to stabilize the camera's temperature was by placing it on a frozen gel pack.

NEX Testing Continues

While I await delivery of one more piece and try to arrange for thermal imaging of the camera recording AVCHD, I thought I'd share this picture of my NEX-5N in the "lab". I call it NEX ICU. An explanation of what you are looking at follows the image. (click image to enlarge)

You are looking at the NEX-5N on edge, mounted on a tripod, pointing down, with no lens attached.  The LCD is elevated.  The surface temperature sensor is taped into the flash threaded insert.  A small fan, about the size of a nickel, sits on the back plane. The HDMI, USB and AC adapter cables are connected after passing through a container containing a frozen gel-pack.

All these measures, to a greater or lesser degree, reduce the rate of temperature gain in my NEX-5N, recording video at the highest resolution, under my test conditions ; yet none of them individually, nor all of them and more, taken together, have been, thus far, able to stem the rise in temperature and the seeming inevitability of thermal shutdown.

I expect to have a final report on my findings in about a week.

NEX Overheating Problems Solved

NEX Overheating: More Surprises Revealed

Since my last post (Nex-5N Thermal  Shutdown Issue) I've been doing a series of tests on the effects of various heat sinking arrangements to see if I could achieve a goal of 1 hour recording time without any notification of thermal overheating (NOTE: the camera has an intentional, 30 minute, maximum continuous record time for apparently unrelated reasons).

All my efforts thus far have failed.  And I've tried many things, including removing the top of the camera (4 impossibly small screws) to see if it would help rid the camera of excess heat.

Finally, I became convinced that the problem was that heat accumulated in the top of the camera, and due to the LCD hinge arrangement, warm air could not escape quickly enough.  I determined to test this by inverting the camera.

But I had conflicting results.  I tried it at night and seemed to have initial success, but the battery depleted before I could finish the test.  I recharged the battery overnight and in the morning re-ran the test.  Immediate failure.  Perplexed, I added the heat sink back in.  What follows are the very surprising results.

TEST CONDITIONS  ("D" = Different from first round of tests)

The temperature probe is placed in the threaded coupling for the flash at the top of the camera. (D)

The label is OFF (see earlier posting above)

A heat sink of 1/8" tapered aluminium bonded with 3M 8810 thermal PSA tape is present in all cases (D)

The LCD is open approximately 15 deg. and not articulated (D)


RESULTS

CLICK ON THE CHART FOR LARGER VIEW

THINGS TO NOTE ABOUT THE GRAPH

1. "30 minutes" indicates the camera successfully recorded for 30 minutes, stored the data and returned to idle status with no issues.
2. There might be a modest effect of increased ventilation of having the camera inverted, but this is not the main issue.   Remember, the surface temperature sensor is, for these tests, located on the top of the camera.  Logically, one would expect that to be the hottest in the upright position and coolest in the upside down position.  It may be that there is almost no effect on the cooling of the camera electronics.
3. The rate of temperature gain at the exterior diminishes with back-to-back recording.
4. The initial recording displays the high temperature warning for some period of time and then shuts down.
5. The warning light is NOT displayed during the second and third recordings which complete successfully even at substantially higher temperatures.
6. Shutdown occurs almost immediately after the 3rd recording.  The warning my or may not have appeared.
7. After a 5 minute cool-down the camera may be able to record for an additional extended period.  (Test aborted in the upside right case only because results were already clear).
8. In this (and in all other tests I've done without exception), the camera asymptotically approaches some stasis temperature, but never flat lines.  That is, (according to my tests and under the test conditions) even after extended operation, and with significant addition of heat sinking material, the camera is still generating more and higher heat than these measures are able to shed.

NOTE: The delay in restart after the second recording is purely a failure of attention  on my part.  The  same delay was added to the second test.

DISCUSSION

Well, where to begin.

How to explain the successive decrease in the rate of measured temperature gain and the successful recording of two segments after the initial failure?  Some ideas already mentioned by others:

• Does the battery generate more heat on initial discharge than when somewhat depleted?
• Conversely, does the battery itself act as a sink when depleted?
• Do the thermal materials perform better once heated?

And some of my own:

• Does the thermal algorithm look at rate of change as well as maximum temperature?
• Is cooling enhanced at higher temperatures by modest convection effect?
• Does the LCD, slightly opened (and importantly, not tilted (articulated) , maximize its function as a heat sink and/or enhance any venturi effect?

Certainly it seems clear that the camera's initial shutdown is premature in light of its successful operation at higher temperatures.  The lack of a warning light at high temperature shutdowns with low slopes supports the idea that the warning light may only be coupled to rate of change.

If this is true, then it seems this could be fixed in software.  Given the rapid rate of cooling after shutdown or even in idle state, sensing the rate of change seems unnecessary.

It seems very strange that the camera doesn't appear to reach a maximum temperature much earlier.  Totally speculation on my part, but it seems similar to behavior of an open feedback loop or a process spinning out of control.  

NEXT STEPS

I've ordered the AC charger to test the effect of removing the battery and some conventional heat sinks to test the original suggestion of richg101  to add DRAM heat sinks in this post.

I've even order a very tiny cooling fan.

Sony NEX-5N Thermal Shutdown Issue

I own an NEX-5N and as others have reported, I have experienced auto shut-off and thermal shut-off.  I had read of others using heat sinks to cool the unit, and I thought I might make a custom one for this purpose.  On advice of friend, I bought a surface temperature reader (About $90 from Vernier).

From it I got some interesting profiles.  But to read the chart you need to know what "Label ON"  and "Label OFF" mean.  Pictured below is the NEX-5N with the LCD open to reveal the back with a label that I've already begun to pry up with an X=acto knife.

And surprise, there is a carefully designed heat sink already in place.

And now the data.  Click on the chart below to see a larger view.

DISCUSSION

First, I only tested one camera; mine.  Your mileage may vary.

The steep drops are characteristic of thermal shutdown which turns the camera off.

The slightly shallower drop is characteristic of timer shutdown which returns the camera to idle.

The jittery lines are characteristic of having the LCD open.  For these tests, LCD open means the LCD as far vertically over the camera as possible with the screen remaining parallel to the back plane of the camera.

Clearly the combination of removing the label and opening up the LCD greatly reduces the thermal load.  (How much open the LCD has to be I will investigate next.)

However, this is not sufficient to keep the camera from turning off.  I believe the reason for this is the 30 minute Power Saver feature which has a variety of settings up to 30 minutes, but no "never" setting.

As the lowest line on the chart shows (Idle, Label Off, LCD Closed) the off time can be extended in idle mode by accessing the MENU (as I did at about the 13 minute mark).

I have tried to find a way to do this in video recording mode, but without success.  MENU is not an available function and adjusting the ISO or the Exposure Compensation did not reset the Power Saver timer.

Of note, even in the last case, the thermal warning indicator did come on at around the 25 minute mark.

CONCLUSION

Obviously Sony knew this was an issue.  Otherwise why would they have built in thermocouples, warning indicators, automated shutdown sequences and punch 150 plus holes in the back of the camera?  

The combination of the label and the full closure of the LCD (of lack of closed venting) is an issue.  

If my analysis is correct, Sony should add a "never" setting to the Power Saver mode.

Sand Box

For years I have been continually frustrated by all my attempts at storing sand paper.  Of late I tried creating dividers in a milk crate, but invariable the paper would slump to the bottom and the whole box would be a mess with the 5" sanding discs for the electric sander.   I've had a design for a box in mind for quite some time, but just now had some time to slam it together.

Found these very small  brass card pulls at House of Antique Hardware

It's a hefty box with 7 1-inch drawers each holing the rectangular and round papers of each grade.  Usually 60, 80, 100, 120, 150, 220, 600.  A place for the sander, sanding block and a some odds and ends on top.  The handle folds down.  The drawer faces were cut from a single piece of salvaged Doug fir.  The drawers glide on their bottoms into dado cut channels on the side

It still needs some drawer knobs (maybe?), but it's already functional and a big improvement.

More Cutting Boards

I've been meaning to make more cutting boards. Having a few, thinly cut strips of wood left from doing the sand box I decided to glue them up to some walnut. But the resulting board was smaller than I wanted. The walnut stock I had was cut to about 2"x3" and I thought it might look good to suspend the laminated portion between end caps that would serve as massive feet. The result...

Back: Light wood for both was from a single 4x4 x 3' old growth, vertical grain Doug Fir.  Front is salvaged Doug Fir.

I was very pleased with the look and quickly made two more.  I have a fourth one that is even more ambitious in the final gluing stage now.

From Scratch

SCRATCH is a relatively new computer programming language from MIT.  Designed to teach kids the elements and structures of programming, it nonetheless offers a lot of sophisticated and powerful features.  Its keys to success are: a drag-and-drop interface, minimizes need to  the syntax exaclty right.

While trying to play a homemade civil war game with Campbell, and finding the decision making quarter landing far afield, I determined to make an electronic one using SCRATCH.  I knew of SCRATCH because it was used in his school and we had started coding a little video game together.  fact, below is version V, but versions 1 and 2 were developed with  Campbell.

Learn more about this project \