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 …..

4- The box , 3D realization

The printing of the CALIBREX box requires more than 8 hours of printing with layer height set at 0.2mm and 20% of printing on the two 3D printers tested. The servo motor palette must be printed with White plastic, the M42 female screw ring must be printed with more care, so a layer height of 0.15mm or even 0.10mm is required with a filling rate of 100% for maximum rigidity.

An overview of the closed CALIBREX calibration box without optics and without electronics, black PETG printing, prusa MK3 i3 3D printer – Pierre Dubreuil.
Exploded parts of the CALIBREX, the M42 ring and the slide are to be glued with epoxy glue once the parts have been cleaned. The servomotor palette is not visible here. The M42 ring is to be printed in 0.10mm or 0.15mm to reach the fineness of a screw thread necessary for screwing in an M42 Male / 2 ″ flowing ring to buy in metal.
The only part to print with White wire is the palette, but it is possible to print it in Black and paint the central reflection area in white afterwards. Here installation of the pallet on the ServoMotor

The files necessary for 3D printing in STL format can be downloaded from the links below. The nomenclature number is also indicated:

Printing of the CALIBREX case in black PETG, 3D printer prusa MK3 i3 – Pierre Dubreuil.
Printing media placement area.
The supports calculated by PrusaSlicer.
The cover placed on the Prusa slicer went for 3 hours 55 minutes of printing with my old Vertex K8400 print density 20% and layer thickness set at 0.2mm.

4- Control software


As you already know, the Calibrex module is equipped with an electronic card, the manufacturing of which we have just seen, with the list of necessary components, and above all the very simple manufacturing circuit board, which is equipped with an Arduino “nano”. You can get it on the net easily and for a very small fee of a few euros.

It is necessary to install the interface IDE Arduino on the Arduino site, you take the latest version 1.8.10, it is necessary to connect your Arduino “Nano” by a USB cable (mini USB socket on the side of the Nano). Finally configure “nano” in the type of card, in the help this is well explained.

Finally once connected select “file”, “open” and you access the “Spectro_nano_embedded” directory. In the directory there are three files (CPP file, H file and Arduino file) you will have to click “Spectro_nano_embbeded.ino” which is the arduino file.

1- Open the Spectro_Nano_embedded.ino file.
Note the Messenger.cpp and Messenger.h files must be in the same directory.
2- Connect the arduino Nano to the computer via USB and upload the driver. (Arrow at the top left)


Once powered, three modes selected with the switch of the box are then available.

1- The local operating mode, by successively pressing the push button on the box, the color of the multicore LED determines the commanded function, when starting the Arduino the “Clear” function is selected.

Color of the
Multicolored led
Pallet positionDenominationUVEX Fonction
light offopenedClearSpectrum acquisition
RedclosedNeonwavelength calibration
Green closedFlatInstrumental response

2- The remote mode allows with most astronomy software (Maxim, Prism …..) to remotely control via the USB cable, the 4 functions described above. In this case, the red power LED flashes quickly, indicating that the connection is well established between the PC and the Arduino. Jean Luc has programmed an Ascom driver which allows the electronic card to be connected to most astro software for amateurs. By choosing the wheel driver with ASCOM spectro filters you can then select the different functions (“Clear”, neon, flat, close acquisition).

Ascom filter wheel driver – ASCOM.Spectro for controlling calibration lamps
Dialog box under Prism which allows you to control the activation of CALIBREX calibration lamps.


For those who do not use Prism, MaximDl software …. Pierre and Jean-Luc have developed the Calibrex control application in C #, a small application for dialogue with the electronics of the nanoArduino at the heart of the caliber. The Calibrex Control V1.0 application runs on its own and updates automatically, it only needs the SpectroWeel ascom driver installed. Once connected to the driver, the 4 buttons allow you to control the 4 previous functions, the active function is very easily visible by the flashing of the colored rectangle to the right of each button.

Par défaut à la connection de l’application la fonction clear est sélectionnée

CALIBREX control v1004
By default when connecting the application the clear function is selected

2- Autoguiding

The principle

The autoguidinge system is based on a recovery of the focal plane of the telescope by two identical achromatic doublets with a focal length of 50mm. The final magnification is 1: 1 which means that the slit guidance is as if the camera were at the focus of the instrument. The slit is inclined at an angle 15 ° relative to the horizontal to release the optical return from the central field, then a mirror causes the beam to exit at 90 ° from the main optical axis. The double achromatic doublet then makes it possible to focus the image of the slit on the guide camera.

Optical guidance system on 1: 1 magnification slot

The slit is an integral part of the UVEX, it is also described in the section dedicated to the spectroscope. This section regarding the slot remains valid when using the Shelyak Alpy guide cube.

The autoguiding system is produced by a reflective slot inclined at 15 ° to the optical axis. The slitting system is that of the basic module of the Alpy 600 from the company Shelyak which consists of a very thin blade (50µm) in nickel engraved with 4 slots (25µm 50µm 100µm and 300µm) with a 25µm hole very practical for UVEX settings. The size of the 4 slots is very useful for adapting the flow resolution ratio depending on the objects and the telescope used. The slit system is very fragile. It is a very sensitive point of the spectrograph that it will have to be handled with care and installed upside down as we will see later.

Shelyak slot system here installed on the spot for the Alpy 600, to be mounted upside down for the UVEX
“Alternative” slit of the basic version of the ALPY 600. Source Shelyak.

Standard slit present in the basic version of the ALPY 600 – 1 hole of 25 µm and slots of 25, 50, 100, 300 µm. Source Shelyak

Each slot system consists of a 50 µm thick nickel sheet produced by electro-deposition. What constitutes a series of slots and “Clear” type holes, the light therefore does not pass through glass passing through the slot. This slot has huge advantages as described by Christian BUIL in an email exchange in April 2019

… If we summarize the interests of this solution:

  • An economical solution
  • A gain in transmission of around 8% and even stronger in blue and UV.
  • No stray reflection (the double image in the guide camera which disturbs beginners and sometimes systems).
  • An ink black in the heart of the slot, which will significantly improve the quality of guidance for all observers.
  • A reflection coefficient of nickel higher than that of chromium (therefore, guidance on potentially weaker targets).
  • More contrasting spectra (less diffusion) – Great flexibility (many slots on the same plate, and a key thing for UVEX, holes which simulate a star, which can be key for the adjustment of the spectrograph
  • this also applies to the whole range of Shelyak spectros (?), but admitting all the same that this nickel slot is less pros than glass slots).

… If we summarize the interests of this solution:

  • An economical solution
  • A gain in transmission of around 8% and even stronger in blue and UV.
  • No stray reflection (the double image in the guide camera which disturbs beginners and sometimes systems).
  • An ink black in the heart of the slot, which will significantly improve the quality of guidance for all observers.
  • A reflection coefficient of nickel higher than that of chromium (therefore, guidance on potentially weaker targets).
  • More contrasting spectra (less diffusion) – Great flexibility (many slots on the same plate, and a key thing for UVEX, holes which simulate a star, which can be key for the adjustment of the spectrograph
  • this also applies to the whole range of Shelyak spectros (?), but admitting all the same that this nickel slit is less pros than glass slots).
“Standard” model which equips the ALPY600 spectroscope in Basic version, installed upside down on the support in 3D printing of the UVEX

Be careful however not to forget to mount the slit upside down on the slit support provided for the UVEX, which is counter-intuitive. Indeed, the edges of the slit do not have the same cutting edge on the two sides at the base, this slit not being made for automatic guiding at the base.

Slit at the place, bad configuration the slit is very wide, we cannot effectively guide in this configuration the lips do not reflect the light of the star once in the slit.

Slit upside down, good configuration we notice that the slit is surrounded by a very fine characteristic line. Be careful not to trust the writing direction (35 µ) here because of the mirrors affected at the time of acquisition by the camera software.

The spectrograph side the diagram above is the one where the width of the slits is written in µm, but the writing is also visible on the other side upside down. Source from Shelyak technical documentation.

The inclination of the slit allows all the light flux that does not pass through the slit to be returned to the guidance system at an angle of 30 ° to the vertical which releases it from the optical axis. The field of vision is taken up by a Thorlabs ME05-G01 1/2 “and 3.2 mm thick plane mirror tilted at 60 ° in the direction of the focusing system.

The 1/2 “guide mirror and its support in 3D printing, the part protected by a blue plastic film is to be installed in front is the aluminized part of the mirror.

The beam is then made parallel by a first achromatic doublet Thorlabs AC127-050-A. A second doublet (same reference as the previous one) focuses the image of the slot on the CCD sensor of the guide camera.

1/2 “Thorlabs Achromatic Doublets (x2). Take care when mounting in the support, the two doublets must be mounted head to tail, the bulging parts towards the inside of the tube.
The two achromatic doublets mounted in the SM05L05 Thorlabs support, the references are oriented outwards.

The guidance system has a 1: 1 magnification ratio which implies that the size of the objects on the slit therefore at the focus of the telescope have the same size on the sensor of the guide camera.

Image of the Caliberx n ° 2 guide field, Zwo Asi 120N guide camera, note that the border around the slot is clearly visible, and that the latter is very fine, this means that the slot is well mounted upside down on its support
Field of the Be EW Lac star, Perl Vixen fluorite 90/810 + Caliberx n ° 2, Zwo Asi 120N – 9s exposure, the field here is 19.5 ‘x 14.5’ limit magnitude 15, condition of urban shooting. When pointing in the direction of the Milky Way many stars appear in the guide field in a few seconds of poses, which allows an astrometric reduction and a precise and sure aiming of spectroscopic targets even up to a magnitude 15!

The field of the guide camera therefore depends on the focal length of the instrument and also on the guide camera used, but the very particular geometry of the slot imposes constraints. First of all, the optimum field of sharpness is ensured at the center of the slit or overall the geometric deformations are not annoying as long as the object is located in the zone between the central screw and the screw n ° 2 visible in Chinese shadow ci -above.

Position of the sharpness field on the slit system.

Basically the area of ​​sharpness is 4mm x 4mm which is compatible with the ZWO Asi 120N camera (4.8mm x 3.6mm sensor) but larger sensors can provide added value in terms of field which is not negligible when pointing. Even if the astrometric reduction can only be done in the area of ​​the sharpness field because of the shadow of the two screws (right and left on the photo) a target appearing in the wider field allows manual refocusing on the slot.

L’attribut alt de cette image est vide, son nom de fichier est image-12.png.
Nebula M42 – C11 Edge + Calibrex + Asi ZWO 178MM 5s of 4×4 binning pose.
L’attribut alt de cette image est vide, son nom de fichier est sn2020ue.jpg.
Supernovae SN2020 eu – C11 Edge + Calibrex + Asi ZWO 178MM 20s of 4×4 binning pose 500/900 gain. The field is extended here, the central screw is visible entirely on the left and half of the screw n ° 2 is visible on the right. We can see the hole at the top left. The field at the top and bottom of the central screw can be used for pointing.

The field is therefore limited by the size of the sensor for a sensor whose dimensions are less than 4 mm, which is not generally the case. For the majority of cases, the dimension therefore depends on the focal length of the instrument as can be seen in the table below.

Focal length (mm)Central field in ‘arc

1- Introduction

What is it about?

Calibrex combines in a single module 42 mm thick, a calibration system and a slot tracking system compatible with UVEX 3, all in 3D printing.

3D model of the Calibrex case here in red assembled with the UVEX 3 in gray.

UVEX claims to be an easy to build instrument. It uses 3D printing for mechanical production and uses standard components that can be purchased from companies like ThorLabs (for mirrors, the network, the lens). At the origin of the project, UVEX is perfectly integrated into the Shelyak Instrument system, the slot, the guide cube and the calibration box are those proposed by the company for the ALPY 600 spectroscope. UVEX being a low cost DIY project (Do it Yourself), it was natural to offer a Guidance and Calibration system in 3D printing, only the remaining slot to order from the company Shelyak.

In situation, UVEX 3 + Calibrex, installation on a C11, Zwo Asi 178MM guide camera.

Thus was born the Calibrex project which offers a single compact box which combines the functions of slit guidance and calibration with Argon / Neon lamp (lamp present in choke blocks for fluorescent tube) and a Tungsten lamp.

Model n ° 2 which equips the ALPY600 spectroscope in Basic version, installed on the 3D printing support of the UVEX 3.
Neon / Argon lamp present in the ignition choke of fluorescent tubes. These starters for a few euros provide a good light source necessary for the calibration of the spectra.

L’attribut alt de cette image est vide, son nom de fichier est guidage_fente_atlas-C2019y4.jpg.
Image of the guidance, Comet field C / 2019 ATLAS Y4 April 04, 2020 – C11 + Calibrex – Camera ASI ZWO 178MM 2s of 4×4 bin pose.
Spectrum of the internal neon calibration lamp in the caliber, 30s of installation UVEX 300 rpm + ATIK 314L + bining 1×1

The electronics are based on Arduino Nano which contains a microcontroller for flash memory and a mini USB port. The lamp control program is therefore saved in the arduino. The control of the lamps and the tilting of the reflector is carried out either by direct control via a switch on the side of the box, or by software via a dedicated ASCOM driver, filter wheel type driver.

Under the hood, on the left the Arduino Nano, the transformer, the connectors, on the right the servo motor with the paddle before mounting as well as the Relco lamp. Note the white circular arc mounted on the servo motor allows to obscure the telescope field during calibration. Here you have to paint it black and keep white a central area of ​​a few millimeters in the center. This simulates the opening of the field at F8. Thus the lines of the lamp of the calibration lamp are thinner which gives a more precise calibration.

A switch on the side of the box selects the remote mode, and the manual mode. In remote mode the switch is deactivated, the command is made exclusively via the CALIBREX USB port. The clear position allows to realize the spectra of the targets as well as the autoguiding, in neon position the ArNeon calibration lamp is on and the palette obscures the beam of the telescope, for the flat position the tungsten lamp is on, and finally in closed position no lamp is lit but the palette obscures the field of the telescope.

Ascom filter wheel driver – ASCOM.Spectro for controlling calibration lamps

From the Ascom driver, you can control the Calibrex box remotely, making it compatible with Remote mode. The advantage of diverting a filter wheel driver and being able to automate the alternation between object spectrum and calibration sequence acquisition in the same way as a three-color imaging sequence via the software automation interface. acquisition of the Prism or MaximDL type.

Boite de dialogue sous Prism qui permet de contrôler l’activation des lampes de calibration du CALIBREX.
A team effort, the Nice people, from left to right, Stéphane Ubaud, Alain Lopez, Jean Luc Martin, and Pierre Dubreuil.