Spectrograph

Spectrographs

1. LECHES (Long ECHElle Spectograph)

LECHES First Light on 21.05.2002 with the spectrum of a neon lamp. Colour photo from a digitial camera

Prisma table (in workshop)

2. FIASCO

And the second generation came with FIASCO (FIbre Amateur Spectrograph Casually Organized).
We've built three of these spectograph, the first one with a 512x512 front illuminated CCD camera as detector (in fact, the same camera as in PONCHADO). The second one with a 512x512 back illuminated CCD camera. These first two cameras were manufactured by Hale Research (UK) unfortunately out of the market nowdays. The third FIASCO was built with a 1024x1024 back illuminated CCD camera from Finger Lakes (USA).

Picture of FIASCO. The configuration is the same as Ponchado but the reduction of stray light and mechanical stability are highly improved. As PONCHADO, it can be equipped with three different gratings: 600, 1200 and 1300 grooves/mm and blazed at 400, 600 and 500 nm respectively.

Another picture of FIASCO without the top cover and with labels for its different components. In this configuration the photo-objective has been substituted with a simple doublet-lens like in the collimator.

Model in 3D of FIASCO spectrograph showing its components. In front (red) the CCD body, in blue the coupling ring, and in green the photo objective.Above and right the difraction grating and its turn-table. In the middle and above the collimator. Above and left the fibre conector.

(Modelling courtesy of Eduardo Ortiz Ostale)

3D model of FIASCO with path light simulation.

(Modelling courtesy of Eduardo Ortiz Ostale)

Another 3D perspective.

(Modelling courtesy of Eduardo Ortiz Ostale)

3. Ponchado

The history of our first stellar spectra with a fibre spectrograph started in 1993 with a test bench spectrograph. The configuration used at that time was the "crossed Czerny-Turned" design with spherical mirrors. This configuration was very compact but unfortunately generates high astigmatism. Since our spectra are limited by dark current noise and the spectrum spreads 10 to 14 pixels perpendicular to the dispersion, this configuration was abandoned. After some trials, we finally adopted the classical "textbook" layout but with an objective lens as camera to reduce all aberrations at a maximum. The result is shown in the figure below. Ponchado borned, which means robust or strong in familiar mexican language.

The spectrograph together with the CCD camera and controller. The laptop displays the spectrum of Comet Hyakutake

Anatomy of Ponchado showing the shutter, the Collimator (f 300 mm, F/6), the grating (600 grooves/mm and blazed to 500 nm) mounted in a rotation stage, the camera objective (f 100 mm, F/2) and the CCD camera (Hale Research, Tektronix 512 x 512, 27 microns pixel, Peltier cooler).

These curves show the total throughput of the fibre and spectrograph optics: 135 microns fibre (including FRD); Collimator; Grating (a) 600 grooves/mm and blazed to 500 nm, (b) holographic 1200 grooves/mm; and objective Canon f 100 mm.

Our detector was a front illuminated CCD from Hale Research (UK)

	Picture of FIASCO. The configuration is the same as Ponchado but the reduction of stray light and mechanical stability are highly improved. As PONCHADO, it can be equipped with three different gratings: 600, 1200 and 1300 grooves/mm and blazed at 400, 600 and 500 nm respectively.
	Another picture of FIASCO without the top cover and with labels for its different components. In this configuration the photo-objective has been substituted with a simple doublet-lens like in the collimator.
	Model in 3D of FIASCO spectrograph showing its components. In front (red) the CCD body, in blue the coupling ring, and in green the photo objective.Above and right the difraction grating and its turn-table. In the middle and above the collimator. Above and left the fibre conector. (Modelling courtesy of Eduardo Ortiz Ostale)
	3D model of FIASCO with path light simulation. (Modelling courtesy of Eduardo Ortiz Ostale)
	Another 3D perspective. (Modelling courtesy of Eduardo Ortiz Ostale)

	The spectrograph together with the CCD camera and controller. The laptop displays the spectrum of Comet Hyakutake
	Anatomy of Ponchado showing the shutter, the Collimator (f 300 mm, F/6), the grating (600 grooves/mm and blazed to 500 nm) mounted in a rotation stage, the camera objective (f 100 mm, F/2) and the CCD camera (Hale Research, Tektronix 512 x 512, 27 microns pixel, Peltier cooler).