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Baader DADOS Slit – Spectrograph

SKU 2458550

Availability: Immediate Dispatch

  • DADOS Spectrograph for astronomy investigation or educational instruction
  • Optimised for telescopes up to 14”/355mm aperture at f/10.
  • Can be used visually or for spectroscopy imaging purposes
  • Choice of 3 slit sizes: 25, 35 and 50 µm
  • Default grating of 200 l/mm for low resolution 
  • Micrometer for fine positioning of the central wavelength.
  • Accepts most CCD and DSLR cameras (with optional adaptors).

Astronomical spectroscopy is a becoming increasingly popular with amateur astronomers. In the past universities, research institutions and professional observatories were the only ones doing such activities. Now the cost of such devices have firmly placed spectrographs well within the reach of amateur astronomers, schools, universities and small private and public observatories.

The DADOS® (Spanish for dice, due to its boxy dice like appearance) - is a  user-friendly slit spectrograph, made by Baader Planetarium, and was first developed at the Max-Planck-Institute for Extraterrestrial Physics in Garching, Germany.  It was originally designed for use in schools or universities and for amateur observers. It offers features of a professional-level spectrograph and can be used for astronomical investigation or for instructional/educational use.

DADOS Spectrograph with a DSLR Camera attached and showing an additional grating

DADOS Spectrograph showing a DSLR attached and an additional optional grating. 

The DADOS spectrograph's main features include:

  • Optimised for telescopes up to 14”/355mm aperture at f/10.
  • Choice of 3 slit sizes: 25, 35 and 50 µm
  • A red LED provides background illumination of the slits for easier focusing of a self-guiding camera
  • Default grating of 200 l/mm for low resolution (optional 900 l/mm grating for higher resolution)
  • Micrometer for fine positioning of the central wavelength.
  • The objective camera port has a built-in wide focusing range and uses the standard T2 adapter thread (M42 x 0.75).
  • Accepts most CCD and DSLR cameras (with optional adapters).
  • The camera interface is a T2 adapter with a standard M42 x 0.75 thread.
  • The wide 55mm focusing range is suitable for attaching a DSLR-camera.

Optional storage carry case, calibration lamp, blaze reflection gratings and autoguding software for spectroscopy are also available.

Examples of work that can be done with DADOS include: Lunar, binary star, novae/supernovae, classification of stars and nebulae spectroscopy. See >>HERE<< for work tutorial examples. 

Note: The DADOS comes with a 200-line grating as standard. A grating with 900 lines or 1200 lines can be ordered for an extra charge. If you need additional gratings for your DADOS, these have to be ordered separately (and especially optically adjusted for this device). If you already own a DADOS, we must ask you to return your DADOS each time to us when you order another grating, apart from the standard 200 line grating. The initial calibration of the grating in relation to the mechanical body of the DADOS must be one here one time.


The DADOS spectrograph has the following features:

  • Two diffent reflection gratings and a specially designed optical system deliver a high light efficiency
  • micrometer gauge for precise adjusting of the grating
  • in contrast to spectrographs without a slit, even large objects (nebulae, planets, comets) can be analyzed – just like in a professional observatory
  • the spectral resolution (lambda/delta lambda ~ 500) makes a precise spectral classification of stars possible
  • the complete visible and near infrared spectral range (350nm – 950nm) can be covered with e.g. an SBIG ST-7
  • the slit is directly visible with an eyepiece or webcam, which makes it easy to center and guide a star
  • the slit spectrograph can even be used at fast optics up to f/6.3, although a slight vignetting is visible at optics faster than ca. f/10
  • fits at standard 2" focusers
  • compact, can even be used if there is not much space
  • the spectrum of brighter objects is directly visible in an eyepiece
  • there are three slits side by side (25/35/50µm)
  • the slits can be illuminated from the back with a red LED for easier focusing of a camera on the slit
  • the spectra can be taken with web-, digital or CCD-cameras
  • all cameras and eyepieces can be attached with our T-2® adapters

DADOS: Properties

Grating Dispersion at 550 nm spectral resolution lambda/delta lambda 
at 550 nm with the 3 slit diameters
spectral range covered
lines/mm nm/mm nm/ 9 µm Pixel 25 µm 35 µm 50 µm ST-7/ST-402 ST-8/ST-1603
200 47,61 0,443 543 388 272 328 656
900 12,67 0,114 3818 2727 1909 87 174


DADOS Reflection Gratings

Three reflection gratings are available are made from a special master gratings. The Blaze angle of the gratings (as well as the optics, see below) are matched perfectly to the geometrical and optical properties of the DADOS®.

  • #2458557 Reflection Grating with 200 lines/mm, cemented onto tilting grating holder (supplied)
  • #2458556 Reflection Grating with 900 lines/mm, cemented onto tilting grating holder (optional extra)
  • #2458559 Reflection Grating with 1200 lines/mm, cemented onto tilting grating holder (optional extra)
DADOS Reflection Grating
Baader DADOS Blaze Grating cemented onto the tilting holder.

The desired wavelength range can be set with the micrometer gauge. Other gratings with the common size of 25x25x6mm with more or less resolution can also be used with the DADOS®.

DADOS Lens system

The collimator system in front of/behind the Blaze grating is made of an achromatic and a triplet lens system. These were specially designed for the best-possible resolution and are coated with the best available anti-reflection-coating. The collimator lens can be moved over a wide range with a precise 2" Helical focusser, so that (almost) all known CCD- and DSLR-cameras (as well as almost all standard eyepieces) can be focused.


The slits

Besides the gratings, the reflecting slit element with a precisely manufactured triple slit (with gap widths of 25/35/50µm) is the second core element in DADOS. You can see all three slits at the same time and easily choose the right one for each object at a glance.

the slits
The DADOS triple-slit


Baader Spectrograph showing spectra

Look at spectrum through the slits.

Because of the forward-reflecting slit element with razor-sharp, perfectly smooth edges and an additional, sophisticated optical system of tilted mirror and projection lenses, you can focus – just as with larger spectrographs – directly onto the image of the star with affordable, common CCD-guiding cameras or webcams (not inluded) or even with a guiding eyepiece and easily guide the telescope!

Mount and adapting DADOS 

On the telescope side, the DADOS® has a black 2" nosepiece so it will attach to telescopes using a 2" focuser. If you remove the nosepiece, you can use the standard 2" SC female thread inside of the front part of the DADOS® for a variety of other adaptations. We have several adapters for a sturdy connection using this thread, e.g. a 2"/T-2 reducer (# 295 8242) to attach the DADOS® directly to optics with the standard T-2 photographic thread (M42x0.75).

You can also the female 2" thread of the front cube to screw the DADOS® without the nosepiese directly at a Schmidt-Cassegrain-telescope. Use our 2" Locking-Ring (#245 8270) to fix the DADOS® in any orientation - this way, you can even mount it between the fork arms of many Schmidt-Cassegrain with an alt-az mount. Both guiding and imaging camera are mounted in a 90°-angle towards the DADOS® to keep it as compact as possible.

To mount the DADOS® on a telescope or attach other accessories, a clamp with 3/8" and 1/4" thread (#245 8593) and 38mm diameter is available. The two-piece clamp has got a 3/8" thread at the bottom side (a 1/4"-thread is included) and a 1/4" thread on top.

You can use it to mount the DADOS® on a ball-head or a tangent assembly as secondary unit. You absolutely need it in a classroom to mount the DADOS® on an optical bench or for any setup without a telescope. There are plenty adapters available for all kinds of guiding cameras a well as for almost all imaging CCD-cameras – just take a look at our Astro T-2® accessories.

You can attach an optionally available Neon-calibration lamp (#2458590 - not included) with 2"-adaptor and 220V cable to it.

Guiding eyepieces

Two reasonably-priced 1¼" DADOS Kellner eyepieces with 10mm (#1304110) and 20mm (#1304120) focal length are included.

DADOS Kellner eyepieces for guiding

DADOS Kellner guiding eyepieces

They can be used for finding objects and for manual guiding without a guiding camera. A slit illumination (included in the scope of delivery) made of a dimmable red LED helps you to focus the guiding star and the slit itself. It illuminates the slit from the back towards the guiding camera/eyepiece, so that the LED's light will not reach the lens of the collimator.



Below are a couple of example of spectra obtained from DADOS.

DADOS spectrograph result of the Orion Nebula (M42) taken with a 130mm aperture refractor

 DADOS Spectrum of the brightest star in the sky - Sirius - taken with a 130mm aperture refractor.

DADOS: Properties

Grating Dispersion at 550 nm spectral resolution lambda/delta lambda 
at 550 nm with the 3 slit diameters
spectral range covered
lines/mm nm/mm nm/ 9 µm Pixel 25 µm 35 µm 50 µm ST-7/ST-402 ST-8/ST-1603
200 47,61 0,443 543 388 272 328 656
900 12,67 0,114 3818 2727 1909 87 174


DADOS Performance: Resolving Power

  • Resolving power λ / ∆ λ on camera objective axis and 25 µm slit
  • Limiting magnitude for a 300mm Ø telescope with S/N 50 and 20 minutes of exposure time.
    • For the 200 lines/mm grating : mv = 8
    • For the 900 lines/mm grating : mv = 6

200 lines/mm (default supplied grating)

 Theoretical Measured λ (nm)
396 492 @416
606 647 @616
668 723 @697


900 lines/mm grating

 Theoretical Measured λ (nm)
2038 2000 @371
3910 3000 @561
5376 5000 @800


  • Measurements performed w. ST-8 XME w. 9 micron pixel size.
  • The measured resolving power of the 900L grating was limited by the pixel matching.
  • With smaller pixels a higher resolution can be measured.

    WEIGHT (KG) 0.95
    USAGE Perfect for visual and photographic use with or without a telescope. Suitable for amateur astronomers for private use and for spectroscopy education on schools and universities.
    SPECTRAL RESOLUTION with different reflection gratings: up to R = 5000
    OPTIMIZED SPECTRAL RANGE 395-700nm tuneable (ca. 365 - 900nm with 200 L/mm reflection grating)
    BREAK-EVEN VALUE 200 L/mm: m = 8 mag. vis | 900 L/mm: m = 6 mag. vis (30cm-telescope S/N=50, 20min. exposure – see instruction manual)
    MECHANICAL DESIGN Blaze Grating Spectrograph with moveable and exchangable reflection gratings
    FIELD SIZE optimized for sensor sizes: ca. 13x18mm, usable from 6.9 x 4.3 mm (ST-402, ST-1603, STF-8300M, DSLR, ...)
    OPTIMIZED FOR FOCAL RATIO f/10 telescopes
    ADAPTABLE TO DSLR-, CCD- and Video-cameras
    SLIT SIZE Multi-slit plat with three slits 25, 35 and 50μm
    ILLUMINATION manual red LED for Slit-Focusing
    SPECIAL FEATURES 110-page tutorial. Flip-Mirror with callibration unit under preparation
    GUIDING PORT with 1¼"-connection for eyepieces, video- and guiding cameras
    INCLUDED ACCESSORIES DADOS, reflection grating 200 L/mm, 10mm and 20mm eyepiece

    Mechanical Weight (without cameras and eyepieces) 0.85 kg
    Dimensions (see Figure in Part Description) 80 × 150 × 205mm
    Electrical Red LED Battery SR 41 or equivalent

    Operating temperature -10 to +30oC
    Storage temperature -30 to +35oC
    Humidity (relative) 0 to 80 %
    Storage humidity 0 to 60 %

    Collimator focal ratio: f/10 *
    Collimator focal length: 80 mm
    Objective focal length: 96 mm
    Collimator – Camera angle 90 degrees
    Dispersion on axis at 550 nm
    - 200 lines/mm grating: 39.7 nm/mm
    - 900 lines/mm grating (optional): 10.6 nm/mm

    * Using the DADOS with a telescope of lower focal ratio than
    f/10 degrades the resolving power and increases the vignetting

      Included in delivery
      • DADOS Reflection Grating with 200 lines / mm, cemented onto tilting grating holder
      • DADOS 1¼" Eyepiece 20 mm Kellner # 1304120
      • DADOS 1¼" Guiding Eyepiece 10 mm Kellner # 1304110
      • T-2 Quickchanger # 2456313 + # 2453620
      • Focusing Ring Collar 1 1/4" # 1905131
      • Focusing Eyepiece Holder 1¼" # 2458125
      • Allen Key 1.3 mm and 1.5mm
      • Slit-viewer unit
      • Gloves
      • Manual

      DADOS User Manual

      DADOS Tutorial