Astronomy | Joan Oró Telescope
Joan Oró Telescope
The Joan Oró Telescope is managed by the IEEC and is currently the largest telescope in Catalonia.
It has a primary mirror of 0.8 metres and an F/9.6 Ritchey-Chrétien optical system. The Joan Oró Telescope (TJO) was built by Optical Mechanics Inc. (OMI) and is equipped with a 6.15 metre automatic dome manufactured by Baader Planetarium GmbH.
The telescope is named in honour of the biochemist Joan Oró i Florensa, one of the most relevant scientists related to the study of the origin of life. In the midst of Franco’s era, Joan Oró emigrated from Lleida to the United States to work on the research on Darwin’s theories and to answer some fundamental questions: who we are and where we come from. He worked at NASA and participated in the arrival of the first man on the Moon and in the exploration of the planet Mars. On returning to Catalonia, during the 1990s, Joan Oró and the foundation that bears his name were the main promoters of the project to build an astronomical observatory in the Montsec area.
Joan Oró Telescope
Research
The TJO is a multi-purpose astronomical telescope and, as such, it carries out a wide variety of observations related to different scientific cases. Given its size, the main application of the TJO are the time-series astronomical observations, where high cadence or continuity are the main requirements.
Its main advantage is the flexibility of the operating modes, allowing the monitoring of objects for long periods of time, as well as the fast reaction capacity (potentially less than a minute).
Given these characteristics, the scientific cases of the TJO include:
- Exoplanets research (characterising and tracking known planets with transits or selected searches of individual objects).
- Eclipsing binaries (to understand the structure and characteristics of stars).
- Pulsating variables (to study stellar interiors).
- Evolved variable stars (giants and supergiants).
- Stellar activity (to understand the magnetic dynamo system and characterise the behaviour of activity phenomena).
- Variability of active galactic nuclei (related to accretion and matter ejection phenomena).
- Solar System objects (tracking asteroids, NEOs or comets).
- Supernovae (with the ability to observe them from the first moments).
- X-ray binaries (rotational variability, accretion phenomena and radial velocity curves).
- Novae (being able to collect data from the early stages).
- Optical counterparts of gamma-ray bursts (GRBs).
- Any transient astronomical phenomenon in general.
The mentioned scientific cases require considerable flexibility in the planning of the nights, together with the ability of the system to react quickly to the alerts of observations of GRBs, supernovae, or other similar phenomena. Participation in robotic telescope networks implies the ability to make continuous observations. Similarly, the TJO can be used as a follow-up telescope complementary with space missions or other ground-based telescopes that require astrometric or photometric measurements. The TJO offers open time to the astronomical community through competitive proposals reviewed by a time allocation committee.
Joan Oró Telescope
Instrumentation
The TJO is equipped with two instruments: an imaging camera (LAIA) and a medium resolution spectrograph (ARES). It also has a second imaging camera (MEIA2) as a backup camera.
LAIA
The LAIA instrument (Large Area Imager for Astronomy) is the optical imaging camera of the TJO, operational since December 2018. It consists of two components: the CCD camera and the filter wheel.
CCD camera
The CCD camera is an Andor iKon XL with a 4k×4k back-illuminated sensor:
Model: CCD230-84
Manufacturer of the sensor: e2v
Sensor type: back-illuminated
Coating: BV
Number of pixels: 4096 × 4096
Pixel size: 15 × 15 um (0.4 x 0.4 arcsec at the TJO)
FOV at the TJO: 30 arcmin
Sensor size: 61.4 × 61.4 mm
Quantum efficiency: >90% from 500 to 650 nm; >50% in all the range from 400 to 850 nm
Typical working temperature: -50ºC
Dark current: <0.01 e-/pixel/sec at -50ºC
Readout noise: <9e- RMS a 1 MHz
Redout channels: 4
Non-linearity: <1%
Readout time: 8 sec
Filter wheel
The filter wheel is physically attached to the telescope, behind the primary mirror mount. It can accommodate up to 12 3-inch filters that are positioned on the optical axis of the telescope using the rotating filter wheel. There are currently 5 Johnson-Cousins photometric filters installed (manufactured by Custom Scientific): U, B, V, Rc and Ic; 4 Sloan Digital Sky Survey photometric filters (manufactured by Asahi Spectra): g, r, i, z; and an H-alpha filter (Asahi Spectra).
Vignetting
LAIA is designed to cover the entire field of the TJO focal plane. With its 4096 × 4096 pixels, LAIA can cover a field of 27.3 × 27.3 arc minutes. On the other hand, the focal plane covers a circular field of 30 minutes of arc. This causes the edges of the LAIA images to be vignetting. Additionally, the ARES pick-off mirror is also seen in the LAIA field of view with vignetting at the northern end of the field. As a result, the LAIA images will look similar to the one shown to the right.
Standard calibration procedure
The TJO control system is designed to periodically execute the acquisition of calibration images, including bias, darks and flats:
Bias: They are usually taken in multiples of 5 before the start and at the end of each night. Observers are given a minimum of 10 bias images.
Darks: They are obtained just before or after the bias images. The exposure time of the dark images will correspond to the maximum exposure time of the night science images.
Sky flats: These are routinely taken at the beginning and end of the night under suitable sky lighting conditions. When sky conditions do not permit, observers are provided with the most recent flat images available.
ARES
The ARES instrument (Astronomical mid-REsolution Spectrograph) is a fibre spectrograph installed in a dedicated room on the ground floor of the TJO building. ARES allows the observation of bright stars with a resolution of R=12000 in two spectral windows centred at 512 nm and 656 nm.
ARES is designed by Fractal SLNE. It allows performing medium resolution spectroscopy with the following characteristics:
Limiting magnitude: S/N=10 for V=13 mag in 1-hour exposure time
Global transmissivity: >10%
Spectral resolution: R=12000
Two spectral windows: green (from 405 to 530 nm), red (from 630 to 673 nm)
In order to achieve a high global transmissivity (>10%) two telescopes (manufactured by Takahashi) and two VPHs in Littrow configuration are used.
VPHs
The dispersion system of the ARES spectrograph is composed of two VPHs developed by Wasatch Photonics, providing the two spectral windows and maintaining a high transmissivity. Both VPHs are mounted on a rail (prepared to accommodate an additional one) which allows a quick change between them.
CCD camera
Sensor type: BV- back-illuminated, optimised for VIS
Number of pixels: 2048 × 512
Pixel size: 13.5 × 13.5 um
Sensor size: 26.7 × 6.9 mm
Minimum working temperature: -100ºC
Readout noise: 2.8 e-
Dark current: 0.0002 e-/pixel/s
Linearity: better than 99%
Bias: They are usually taken in multiples of 5 before the start and at the end of each night. Observers are given a minimum of 10 bias images.
Darks: They are obtained just before or after the bias images. The exposure time of the dark images will correspond to the maximum exposure time of the night science images.
Spectroscopic flats: The optimal calibration strategy for ARES is still under evaluation. The main purpose of spectroscopic flats is to trace the position of the spectrum and correct the intra-pixel response. For this reason, 4 options can be studied: direct illumination of the CCD, dome flats, illumination of the fibres with LEDs, and standard stars. The solution that provides the optimal result will be used for the spectra images delivered to the observers.