Tilt Adapter for narrow band solar imaging

Imaging with narrow band H-alpha filters for solar imaging (prominences and chromosphere) requires the light beam to be almost parallel before entering the special interference filter called Etalon filter. This is achieved by i.e. telecentric systems, also extending the focal length by a factor of 2-4x. The sensor protection glass and anti-reflection glass of the camera create reflections with each other and the filter surface. Due to the parallel light beam, these reflections create interference patterns, noticable as so called Newton’s rings in the image. It depends on several different factors like sensor construction (micro lenses, …), exact angle of sensor in optical path, angle between sensor and filter / protection glass, … how strong the Newton’s rings influence the resulting images.

It is possible to reduce or eliminate this in post processing. But any minor shift in the imaging train will make it almost impossible to compensate with flat-field images.
Fortunately, there is one alternative option: tilting the camera by a few degrees (usually up to 5 degrees), to widen the distance of the Newton’s rings, where they are no longer disturbing.

As these tilt adapters have a quite steep price tag, I constructed and printed one myself. I had to create several versions, until I had achieved a proper stability as well as stray light protection. But finally, I have a working tool 🙂
If you are interested in the design, you find the 3D files and description here: https://www.thingiverse.com/thing:4301757

See how much the tilt changes the resulting image!
Hints to the images:
– The blurry look in the image with Newton’s rings results from the alignment algorithm locking on the Newton’s rings instead of surface features
– the adapter attached to the filter is a prototype without stray light protection. Hence a strip of black insulation tape was used for shade

Combined charger and trigger cable for Sony mirrorless cameras like A6400

I often capture time lapse image sequences and do astrophotography. In both applications, a trigger cable and a proper means of powering the camera are essential. Keep in mind, that a fully charged battery usually lasts for no more than 3 hours.
At the moment, the only way to power a Sony mirrorless camera for a whole night or several hours is a dummy battery attached to a power supply (be it a mains power supply or a 7.2V battery driven sollution). With the release of the new models recently, like the A7III or A6400, the camera may also be powered through USB charger during image acquisition. (It may still be possible, that the battery drains, but far far less.)

This is really good news, as a USB power bank will provide the juice to run a whole night or even longer! But there arises one new problem: The external trigger remotes use the same USB port as it is used for charging.
This is possible, as Sony has created the so called Multiport some time back for use with their video cameras. The Multiport is an extended Micro-USB port with a second row of contacts. These contacts provide access to some control as well as audio and video output.

I did some research and came across Multiport connectors with solder pads for all 15 pins. See the pinout in the images at the end of the post.

Sony Multiport Adapter

With such connectors I was able to tailor a dual cable adapter, to charge and trigger the camera at the same time! I took a USB cable with male type A connector and a headphone extender cable with male 3.5mm plug. I chose both cables around 1m in length. This should be long enough in most use cases, but not too long to reduce charging performance.

Combined charger and trigger cable for Sony mirrorless cameras


The 3.5mm plug fits some of my trigger devices. All the others have 2.5mm plugs, for which I have adapter calbes in use. Most computer timer remotes with interchangeable camera plug sold, have a 2.5mm female audio jack. See attached image for the typical pinout.

Soldering the two cables to the tiny solder pads requires a steady hand and experience in soldering. The USB as well as the audio cables have quite thin wires (AWG26 to AWG28, which equals to 0.12 mm² to 0.08 mm²), except the USB power wires (AWG22 or AWG24 in quick charge cables, which equals to 0.32 mm² and 0.20 mm²). The wires are rather stiff. Therefore, aligning the wires to the solder pads may be tricky. It gets especially tricky, if the wires are exposed from the outer isolation for less than a centimeter.
Advice: Always check the finished cable for shorts and proper contact with a multimeter!

Soldered Multiport adapter with USB (bottom) and headphone (top) cables

To reduce wear, which may lead to wires breaking off the solder pads, I designed a connector housing / case. The housing holds the adapter as well as the cables in place. Furthermore, this is the only proper way to handle the connector upon pluggin to / unpluggin from the camera.
The connector case is 3D printed. I share the STL file on Thingiverse here:
https://www.thingiverse.com/thing:4279366

Multiport adapter case – 3D model in 2 parts

Disclaimer:
This is a guide put together as reference for me. If you follow this description, you will do so on your own risk. I may not be held responsible for any damage or injury caused!

Camera slider – build complete :-)

After several hours of designing, 3d printing, drilling, soldering and assembling, my camera slider is ready to use! All components are neatly packed within cases, so that the only wires visible are the power supply from the LiPo battery pack and the shutter release cable to the camera. I have several extensions in mind, like a pan-tilt unit. But for the moment, I will test and use the setup as is. The next improvements will be more on the firmware, for more features: non-linear movement, slow start, slow finish, pre-defined profiles, … for more impressive movies.

 

Now, concluding the build, I have the following parts in the final setup:

  •  12 U-groove wheels, matching the carbon fiber tubes (3D printed plus ball bearings)
  • 4 wheel carriages, each holding 3 U-groove wheels (3D printed)
  • 1 case for the microcontroller and motor driver (3D printed)
  • 1 case for shutter release, power supply and connectors (3D printed)
  • 1 hand-controller case (3D printed)
  • 1 battery bracket (3D printed)
  • 2 end-assemblies (5 parts each, 3D printed)
  • 2 supports (3 parts each, 3D printed)
  • 1 NEMA17 stepper motor
  • 1 A4988 stepper motor driver
  • 1 Arduino Nano (Atmel 328 microcontroller)
  • 1 4×20 LCD
  • 1 Joystick module
  • 1 DC-DC converter
  • 2 micro switches with long lever as end switches
  • GT2 10mm timing belt with wire reinforcement
  • 1 GT2 10mm 20 teeth pulley wheel
  • 4 GT2 10mm idler wheels
  • A whole bunch of M3 to M6 screws and nuts
  • 40x3mm flat aluminium
  • 30x50x3mm L-shaped aluminium
  • carbon fiber tubes

The project was really a fun to make. Even more, the resulting slider provides flexibility and transportability! I may configure the slider in any length, depending on the available tubes. The tubes I use, are 37cm in length and have aluminium screw-in adapters to fit one to the other. I have a bag, which I used as personal item in air travel. The bag holds the complete setup for up to 5 meters (exkluding tripods). The bag weighs in at approximately 5kg – so it is a light weight setup for the length possible.

Damascus knife – building the handle

A few weeks ago, I built a damaskus knife blade (see Damascus knive workshop). Now I finally had time to build the handle. Part of the delay accounted for the decision in material and design of the handle. After some serious research and window shopping, I found the perfect combination I would love to have: desert iron wood and silver.
Desert iron wood is a very dense and hard wood. The core parts have a deep red color with wonderful dark texture. But it is not at all easy to find a piece at reasonable prices. Luckily I found an online store, offering a block of desert iron wood with matching size and texture to my likings.
The bolster shall be like a cap, continuing the shape of the handle. As a material I use sterling silver.

The shape of the handle should become rather minimalistic. Further more, I wanted to have some resemblance to traditional Japanese handles. Therefore I chose a prolongued octagonal shape, which gradually gains a bit in height from the bolster to the end.

To build the handle, I started with the wood. I drilled a hole at the exact position to center the blade. Then I used small files to match the hole with the tang, which has a rectangular shape and is a bit off-centered to the rest of the blade. This was really time consuming, as the desert iron wood clogged the files within a few strokes. But finally, after a few hours of work, I had a perfect fit for the tang. I let approximately 5mm of the tang still protruding the handle, to have more strength in the final assembly by hammering the handle on to the blade.
The next step was to make the recessed front, where the bolster will fit in. I cut a line at exactly 10mm from the front edge. Then I filed away 1mm of wood, as I will use 1mm sheet sterling silver. From a strip of 11mm width I formed a ring with an octagonal shape matching the handle, using parallel pliers. The ring is soldered with hard sterling silver solder. After filing and sanding the edges to have perfectly flat sides, I cut a sheet of silver with a bit of excess border. The ring is soldered to the sheet, again using hard solder. After cleaning and filing away the excess material, I could drill and file the hole for the tang. This again was a bit time consuming, to create a perfect fit…

Finally, I sanded and polished the silver bolster, gave the desert iron wood a last fine sanding. Then I mixed a bit of epoxy with desert iron wood file dust. I added glue to the bolster and into the hole for the tang. So I would have a really strong bonding betreen all the parts. I hammered the bolster to the handle (which was only necessary for the final 2mm). Following immediately I inserted the knifes tang to the handle. Using a rubber hammer, I pushed the tang into the final position within the handle.
Meanwhile I set an oven to approximately 70° Celsius for increased strentgh and faster hardening of the epoxy. After cleaning away any excess epoxy with acetone, I set the whole knife in the oven for curing.

Hint: If there is any epoxy pushed out of the joints during curing, you may use a small soldering iron to work the exopy off the surface. The remaining thin film of epoxy may be removed with acetone. If you are careful, you will most likely have a scratch free surface afterwards!

The last thing to do is a thin coating of hard oil.
After more than 20 hours of work (including forging the blade), the knife is ready 🙂 The final result is a perfectly balanced knife due to the heavy wood handle. The center of balance lies exatly in front of the bolster. The blade will hopefully last for a very long time and provide perfect cuts due to approximately 56-58 HRC.

Motorized camera slider

For quite some time I would like to create night time movies in hyperlapses. For me, the most stunning results may be created by moving the camera along a linear path by the use of motorized sliders. Motorized sliders, which are more than 2 meters long, have an impressive price tag. Further more, these tools are bulky and heavy, especially when the setup attached to weighs in a few kilos.
Therefore I decided to build my own with a few goals in mind:

  • light weight
  • portable
  • variable length
  • suitable for a load of a few kilos
  • wider range of speeds
  • extendable for rotation axis
  • direct control for camera(s)

To achieve all or most of these goals, I came up with a design built around carbon fiber tubes with aluminum screw-in fixtures. Appropriate tubes may be built from scratch or are readily available for camera gimbals. I chose the camera gimbal extensions, as there is no big price difference to buying stock material. Further more, they come in a handy size of +/- 40cm in length.
The end supports will have to hold the tubes as well as a gear belt, along which the slider cart will be driven. For long setups, I created supports, to prevent bending and excessive stress to the tubes. Both types of support will have legs as well as tripod mount screw holes (3/8 UNC thread)
The slider cart consists of 4 blocks holding 3 pulley wheels each. The blocks are attached to a base plate (in test setup a plywood sheet). In the middle of the base plate lies the motor unit consisting of a steper motor and 4 guiding wheels to create enough tension for the gear belt to be driven by the motor.

All in all, the shopping list is really limited, as most parts were 3D-printed. What I had to purchase or use (most parts were already to be found in the workshop) was:

  • carbon fiber rods (at least 8)
  • 24 ball bearings type 626 2RS (6x19x6 mm)
  • GT2x10mm belt matching the desired length
  • GT2 20 tooth drive gear
  • 4 guide wheels without teeth for 10mm belt
  • 1 NEMA 14 stepper motor, <3V nominal voltage
  • several M5 and M6 screws, washers and nuts
  • 3/8 UNC thread taper
  • approximately 0.5m of 40x3mm Aluminum sheet
  • 25cm of 30x50x3mm Aluminum L shaped profile
  • Arduino, Stepper motor controller like A4988, 12-18V (lithium) battery
  • 1 can of rubber spray like Plasti-Dip (c)

Most of the time I spent was in CAD constructing the parts. Printing took about 3 days. The pulley wheels have to be sanded for a smooth surface before coating with rubber. The remaining time was spent in cutting, drilling and tapering the aluminum parts, before all parts could be attached together.

The first test run was more than pleasing. See for yourself:

The next thing to do is to create a control box with all the features implemented for every day use 🙂

Damascus knive workshop

Today I could participate in a workshop to create my own damascus knive. With the guidance of the really well experienced smith, I could manage to forge a 189 layer blade out of 7 individual metal strips. (OK – to be honest, the essential parts of the forging were done by Walter, the smith). I am really pleased with the final result – my own kitchen knive in Santoku style…

 

Wooden tripod base for small telesope mounts

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Several years ago I purchased my first telescope. The telescope had an EQ2 mount included. The EQ2 is an entry level mount, with an all in one mount and tripod base. The EQ2 served me for some time, until I got frustrated with the instability and bad and worn gears in my unit. So one day I replaced it with a goto mount. The last time I used it was for the 2006 solar eclipse in Turkey. Since then the whole thing had to sit and wait for a long time in the basement.
Several years passed until I added a Sky-Watcher Star Adventurer to my collection of gear (I am really happy with this little travel mount!). To use the Star Adventurer in its full extent, a sturdy tripod is required.
None of my photo tripods (neither aluminium nor carbon fiber) could provide a rigid platform to hold against the vibrations of wind or camera mirror flip. After reading several comments on tripods for the Star Adventurer, the direction was obvious to use a wooden tripod. I was already scanning the market for proper tripods, when I remembered the EQ2, which had quite a nice wooden tripod. The only problem to solve was, to replace the EQ2 head with a flat base. The base should provide a stable means to attach the Star Adventurer with one UNC 3/8 screw…

The design was straight forward: The construction exists of 2 parts. A 3-prongue base to attach to the tripod legs and a raised platform for the Star Adventurer. As I didn’t have a large enough piece of beech wood for the base, I used a 40mmx40mm beech wood block. The block was cut in 3 equal parts. These are mitered at 60°. On the other side, I rounded the top part (a rather aestetical finish) and drilled the hole for the bolt attaching the tripod leg.
The platform consists of one round disc of 40mm thick beech wood, which I cut out with a 100mm circular drill. The 4 parts were then glued together with 2 wooden pins joining each leg part, to enhance mechanical strength.
After drilling the required hole for the UNC 3/8 screw and the recessed hole for the screw head with washer, the whole part was sanded, cleaned and finished with hard oil. The platform top face received a rubber coating for a better hold of the Star Adventurer.

Parts used:
3x 40x40x100mm beech wood
1x 100x100x40mm beech wood (for platform)
6x 6mm wooden dowel

Constructing a clean chamber for camera and lens repairs

When I started to modify second hand camera lenses, I soon found it rather difficult to keep dust away. Especially when I had to disassemble the lens for stuck aperture or compact cameras, I struggled to reassemble without dust on the lenses.
Some time later, I bought a Sony Alpha 6000 camera to modify for full spectrum (see seperate post). This triggered me to research for and build a clean room chamber…

A clean chamber may be constructed in several ways. The most compact and easiest way would be a transparent plastic container with attached rubber gloves. This would be OK for some tasks, but not for a mechanical repair or modification due to the huge amount of parts and tools to work with.
So I decided to go for a biomedical laboratory style system, which uses excess pressure ventilation with clean air. You can think of this as a larger box with a slit on the base of one side, where you operate. A ventilation system creates – preferably a laminar – air flow from the top, which exits through the slit. Before work begins, ventilation is turned on and all surfaces within the chamber are cleaned twice with a couple of minutes setting time inbetween, to remove as much dust as possible. When you move your hands or operate any objects within the chamber, do it slow! Clean all objects, tools and your hands before entering the chamber. The continuous air flow will now prevent dust from entering the chamber and you are good to go.

Construction:
I used 4 sheets of decorative chipboard and a sheet of acrylic glass to contruct the chamber. All board were simply screwed together. In the top board I cut holes for the ventilation. Further more I installed 2 LED lights.
The ventilation is constructed of 3 seperate units. Each unit has a high volume 12V propeller attached to a flat duct system. The adapter for the propeller was CAD designed and 3D printet (available here). In each of the flat duct systems I installed 3 HEPA filters as outlets. So in the complete setup, there are 3 fans with 130cfm (220 m3/h) each (feeding through 9 HEPA filters) and 2 LED

lights. All components are powered by 12V, which makes the electrical setup safe and easy.
Hint on the HEPA filters: I bought the small filter cartridges for vaccuum cleaner robots, on ebay for a dollar each.

Parts used:
2x 40x60cm decorative chipboard (19mm thick)
1x 60x80cm decorative chipboard (19mm thick)
1x 40x80cm decorative chipboard or MDF board (6mm thick)
1x 40x80cm acrylic glass, 5mm thick
3x 120x120mm fan, 130cfm
3x 70cm flat duct 60x100mm
3x 3d printed fan adapter
6x End-caps for flat duct (or plastic sheets to fit)
9x HEPA filters cartridges
2x 3W GU10.3 LED lamp
2x GU10.3 mounts
1x 12V 5A power supply
several screws
mounting adhesive

Total cost was approximately 60 EUR