3- Electronic


The calibration module in the Uvex3 spectro consists of a Calibrex1 electronic card and a few external components, namely a flat lamp and an Argon-Neon lamp for calibrating your spectra.

This set is built on the basis of an Arduino Nano circuit which allows to do many functions in local mode or in remote mode via a PC connected by USB. The printed circuit has been developed by us and its reduced size allows us to integrate it perfectly into the guide module. It is therefore not necessary to have special skills as an electronics engineer or to know how to program everything is already done and explained in the following lines. You can get the printed circuit by following the link indicated and order it online. All you have to do is send the gerber file also available in the rest of the article to the site before confirming the order. You will still have to download the Arduino programmer found on the net so I will give you the corresponding link. The specific program for this Arduino application has been developed by the team. It will also suffice to download it from this article and then transfer it to the Arduino using your PC via a mini USB cable.

If you do everything yourself it will cost you a fairly modest sum not exceeding 50 € for a complete Calibrex card (the printed circuit, the components with the Arduino Nano as well as the two lamps).

The Calibrex1 card with its external components. Clockwise from the left:
12V power connector, Tungsten lamp (flat), Neon Relco lamp, Manual / Remote switching switch via ascom, manual control swtch, Red power LED, Multicolor LED mode indication mode, Servo motor.

We can see on the photo above the set that we will test on the table before integrating it into the guide module. We see the two lamps (Tungsten and Argon-Neon) a switch to switch from local mode to remote mode, a push button to change function when we are in local mode, the external 12V socket, a red LED (power and indicator which indicates the mode), a tricolor Led to know firsthand the function performed, finally a mini servo to switch the reflector.

Calibrex1 card connectors


Not many components on the PCB itself, it’s the Arduino that does almost everything. He manages :

  • Lighting the lamps
  • The cycle, calibration, flat, dark and acquisition
  • Position the servo motor
  • The Usb link with the connected PC
  • Manual mode and remote mode
  • External information lights
  • Measurement of the temperature of the interior housing by an internal probe

The small blue transformer that we see in the photo acts as a voltage booster from a frequency generated by the Arduino. Two separate outputs (with 180 ° phase shift) we attack (via the two transistors T3 and T4) the two primary of the transformer to have an output on the secondary of the transformer an alternating voltage of about 200 V, which will be used to power the lamp of Argon-Neon calibration. The Tungsten lamp is lit by another output of the Arduino via the transistor T1.

The servo motor is connected to the M1 connector next to the blue transformer, and the temperature probe opposite to the P2 connector. All the LEDs are connected directly to the Arduino outputs via a current limiting resistor.

The regulator U2 is used to manufacture continuous 5V from external continuous 12V. It is used to power the 5V servo motor.

Transformer used on the Calibrex1 card with reference on the Conrad site.
Detail of the mini servo used on the Calibrex1 card with the reflector placed at the end.
The electronic diagram of the calibrex card, the arduino nano allows the creation of signals to position the servo motor, it controls the two calibration lamps. A temperature probe can be used and connected to pin 19 … Not yet implemented in the software part. The transformer supplies high voltage (220 V) to the Relco Argon / Neon lamp.
Component layout refer to the list below for wiring.

Nomenclature refer to the screen-printed map for mounting.

ComponentsValue Details
U1 Arduino Nano
TR1 Transformer to
solder for CI
see above
T3, T4 Transistors darlington TIP122 boitier TO-220
T1 Transistor NPN 2N2222 boitier TO-92
U2 Regulator 5V 78L05 boitier TO-92
R1,R2,R4,R5,R6 resistors4,7 Kohms P= ¼ W
R3 résistor24 Kohms P=1 W
LR1,LV1,LB1,LRalim résistors2 Kohms P=¼ W
1 LED tricolor cathod commun Diam 5 mm
1 LED red (light alim en 5V) Diam 5 mm
1 switch , 2 positions Diam 5,5 mm
1 pushbutton , fugitiveDiam 7 mm
1 femel chassis plug, le + in the middle Diam 8 mm
1 associated male connector plug
1 bar support Nano (M/F) 2X31 * pas 2.54 mm
1 bar M for connectors 3 points
1X12 * pas 2.54 mm

The printed circuit is made in China, by the company JLCPCB. I ordered from this manufacturer and the result is perfect, and very serious. The manufacturing quality is remarkable and the prices very low. Just click the surrounded “calculate” menu and take the default page and download the Gerber file as a zip file, all done automatically. I’ll give you a screenshot to show you what it looks like before the final order. You download the Gerber file that I give you. We can notice that there are two holes of 4 mm in diameter drilled, they serve to center the circuit in the calibration module and pass the lug which is part of the module.

Step 1 – create an account then import the Gerber_NEW_PCB_CALIBREX1_20190325130025 zip file above
Step 2 – Order and pay (2 €). We can see on this page two orders placed.

Once received the components, the printed circuit and the servo motor, remains to solder the components and to assemble the whole in the Calibrex case. Here is the result:

Your wired Calibrex unit ready to be tested. Note there are still a few steps before use on the sky: The 31.75mm slide of the guide camera is not glued, the white palette mounted on the Servo (on the left) is not yet painted black. Go courage we have the programming of the arduino, the installation of the Ascom driver and the test phase.

First Uvex3N5 tests

My Uvex was the last built in 3D of the first series of 5, like Stéphane’s, it has the Calibrex module entirely built in 3D as the main box (see photo above).

And the first tests on the sky allow to validate this set. The purpose of this module is to calibrate the spectrum using an internal neon lamp, flats and autoguiding on a slot.

My Uvex was not perfectly adjusted, probably today it remains perfectible, but good with good advice from Christian (see paragraph Uvex) it is done without much trouble.

My equipment astro a Vixen Fluo 90/810 mm scope, which makes an F / D ratio = 9, a good report for the Uvex. We will not go as much in the blue as a Newton telescope open at 10, but to take your first steps it is fine. We can already try the internal neon of the Calibrex module, once it is on (push button) a pose of 2 s is enough to make the spectrum. My CCD camera is an Atik 314+, and the neon was collected in an easy-to-find ballast starter in DIY stores. We can notice that the lines are wide, it is not ideal, it is that we do not have an F / D ratio of 9 in the Calibrex module. We are thinking of a solution by fiber to inject the neon light directly onto the spectro slot. Currently we have the neon which diffuses in the whole of the cavity of Calibrex module and a mask comes to be put in front of the neon by a servo motor to direct part of the light on the slit.

Second solution put the neon in front of the opening of the scope, the result is perfect the lines are clear (argon and neon) the pose is longer 30 s, do not forget to wave the neon in front of the lens. To make this external neon take the choke, open it to remove the capacity, and above all put a resistance of 24 Kohms – 1W in series on one of the two legs and all to be connected to the 220V. We can do this when we are near the house, as a nomad it is different.

Calibrex internal neon pose 2s
External neon pose 30s
External neon

Now let’s make a spectrum of a star, but before we have to put the target star in the slit, it must be vertical and make sure that the displacement of the right ascension of the instrument is perpendicular to the slit. It is enough to position the spectro at the focus and to turn the guide camera fixed on the Calibrex module, in order to have the vertical slot. My guide camera is a 120MM ASI therefore monochrome, very sensitive, and inexpensive. The field of this one is 12 ‘X 17’, I present to you an image of the field of the star EW Lac in the “mirror” comprising the slot. The resulting image is very satisfactory, I re-sized to have the star field and submit it to the Astrometry.net server to determine the limit magnitude. I find a magnitude of 13 which is very good for a 90 diameter scope. I use the PHD2 Guiding software which works very well for autoguiding.

On both sides of the field we see two circles, this corresponds to the fixing of the slit mirror.
Resizing the useful field.
Field recognition with Astrometry.net.
Fields on the C2A software.
25 microns slot lit in front of the tube, we can see it perfectly and as a bonus a star on the left.
Shelyak slot used for the Calibrex module, different widths are available.

Now visualize my first spectra, once the target in the slot and the autoguiding running. I’m not talking about the settings described by Christian, everything is very well explained in the “Uvex” paragraph. It is essential to have clear stars visible on the “mirror” slot and the spectrum science net too, the first session it was not the case, I had simply forgotten to focus the telescope! Do not forget also to make a reference spectrum, a neon for each star and also the offsets, and the darks. I use Isis which works very well and is scalable.

HD358 spectrum

The first HD358 spectrum is not very fine, a tuning of the chain solved the problem. It is a star of spectrum B8IV-VHgMn or can be calibrated on the Balmer lines.

The HD193182 spectrum is fine and clear, B7IV / V(e) Magnitude : 6.51
10 poses of 60 s achieves this result.

Finally some spectra profiles made with the same set up.

Spectra of the Be star 8 Lac A.
The star Be 8 Lac A is located below 8 Lac B
Another Be star: Ew Lac
The Be LQ And

My first comments on this new Uvex spectro designed by our friend Christian, a real gift offered to amateurs, once made in 3D a real working tool that can be changed over time. Currently I use a 300 rpm network with a 25 micron slot, and I work mainly in the visible, but tomorrow I can go with a network of 600 or 1200 rpm, work in the UV or the IR, the flexibility of the Uvex allows it Here are my first impressions, the strength of this spectro is the simplicity of use once well adjusted, and also the pleasure of using something that one has built itself, a real instrument 3D printed scientist …..