Introduction
FastCam is an instrument designed to obtain high spatial resolution images in the optical wavelength range from ground-based telescopes by using the Lucky Imaging technique. This technique is based on the idea of registering the instants of atmospheric stability, typically lasting just some milliseconds, using very short exposures.
The first FastCam was an instrument jointly developed by the Instituto de Astrofísica de Canarias (IAC) and the Universidad Politécnica de Cartagena which started in 2006. Since then, the IAC assumed its operation and it is a common-user instrument at the Cassegrain focus of the 1.52-meter Carlos Sánchez Telescope (TCS, Teide Observatory) and a visiting instrument on the 2.5m Nordic Optical Telescope (NOT, Roque de los Muchachos Observatory, ORM).
. 
FASTCAM#TCS FASTCAM#NOT
During its lifetime, the Fastcam instrument has incorporated different detectors. The instrument consists of a very low noise and very fast readout speed EMCCD camera. Currently Fastcam makes use of an Andor iXon DU-888U3-CSO#BV back-illuminated system. A new update of the camera acquisition software is currently being worked on. A complete characterisation of the detector is also being carried out in order to better understand and exploit all the performances of the instrument, applying particular configurations for each scientific case. A standard reduction of the data is also being implemented in order to offer it to all users of the instrument and it is available upon request.
Technical Data
Andor iXon DU-888U3-CSO#BV back-illuminated system containing a CCD sensor from E2V Technologies:
- 1024 x 1024 pixels
- Pixel size of 13 microns
- 30 MHz max readout time
- 26 fps full frame (96 fps 512×512)
- Preamp gain:1,2
- Electron-Multiplying (EM) gain 0 -300
- < 1 e- readout noise (with EM gain)
- > 95% QE
Some features of the detector are the frame transfer mode. This option is a special acquisition mode that contains 2 areas of approximately equal size as shown below:
1. The Image Area, which is at the top and farthest from the readout register. This is the light sensitive area of the CCD.
2. The Storage Area is located between the Image Area and the readout register. This section is covered by an opaque mask, usually a metal film, and is therefore not sensitive to light.
Frame transfer devices typically have faster frame rates than full frame devices, and have the advantage of a high duty cycle, meaning the sensor is always collecting light. Indeed, Fastcam with an area of 750×750 pixels in frame transfer mode is able to sample the atmosphere continuously with 30 ms images (33 fps).
The Fastcam plate scale at TCS is 0.035 “/pixels with a field of view of 35.8” x 35.8”.
The filters available are those corresponding to wavelengths R, I, Z with transmission curves shown in the graph, where the x-axis is the wavelength and the y-axis is the transmittance.
The optimal Fastcam configuration for Lucky imaging of point objects is with the maximum readout speed of the EM Amplifier (30MHz). With pre-amplifier gain 2 for higher dynamic range and vertical readout speed 4.33 us with Normal voltage amplitude, to avoid charge transfer losses. As mentioned before, the frame transfer mode with a pixels size area below 750×750 allow a rate of 33 fps (30ms images in continuous mode).
With this configuration the following linearity plots have been obtained for EM=0 and EM=300. The rest of the configurations being between these two.
EM=0, Saturation level=21000 ADU – Gain=4.20 e-/ADU – RON(e)= 89.8 e-
EM=300, Saturation level=41500 ADU – Gain=0.01 e-/ADU – RON(e)= 0.22 e-
Readout 30MHz – Preamp 2- EM gain 0
Readout 30MHz – Preamp 2- EM gain 300
Instrument Web Page (Spanish only)
Publications
- FastCam: a new lucky imaging instrument for medium-sized telescopes (ADS)
- High-contrast optical imaging of companions: the case of the brown dwarf binary HD 130948 BC (ADS)
- Orbit Determination of Close Binary Systems using Lucky Imaging (astro-ph)
- Lucky Imaging Adaptive Optics of the brown dwarf binary GJ569Bab (astro-ph)
- Others publications that cite FastCam instrument: (ADS)