Aryabhatta Research Institute
of observational Sciences
3.6m Devasthal Optical Telescope (DOT)
Aryabhatta Research Institute
of observational Sciences
ADFOSC is a low-resolution slit-spectrograph and camera having sensitivity in the wavelength range 350 nm to 1050 nm. It uses a 4096 x 4096 deep-depletion fringe-suppressed E2V CCD camera with a pixel (px) scale of ~0.2 arcsec, and it covers a field of view of 13.6 x 13.6 arcmin. The available filters are broad-band SDSS u,g,r,i,z and narrow-band (10.2 nm width) with central wavelengths at 491.6, 660.9, 674.3, and 683.3 nm. The spectral dispersions provided by different grisms are in the range of 0.1 to 0.7 nm/px and an 8’ long slit with different available widths (0.4” - 3.2”) can be used. Imaging observations show that the instrument has the capability to detect sources up to ~24.5 mag AB (i-band) with 10% photometric accuracy in r-band in effective exposure of ~2 hours in dark nights. Stellar images with a FWHM of 0.9 arcsec in r-band were recorded in May 2020 in the best sky conditions. Spectroscopic observations with the instrument show that a spectroscopic trace of g=19 mag source at a 5-sigma level can be detected in 10 minutes of exposure at ~0.2 nm/px dispersion. Hg-Ar, Ne, and continuum lamps are available for spectral calibration.
| Parameters | Value |
| Type | Imaging and spectroscopy |
| Mount position | Main axial port |
| Wavelength range | 350-1050 nm |
| Array size | 4096 x 4096 pixel2 |
| Pixel size | 15 μm |
| Pixel scale | 0”.2 |
| Field of view | Broad-band imaging: 13’.6 X 13’.6, Narrow-band imaging: 11’ diameter |
| Spectral resolution | <2000 |
| Readout noise | 8 e- |
| Readout time | 35 s |
| Gain | 1.6e-/ADU |
| Minimum exposure | 0.9 sec |
| Available filters | broadband: SDSS u,g,r,i,z and narrowband |
| Grism range | 0.1 - 0.7 nm/pixel |
| Slits | Length:8”, Widths: 0’.4 - 3’.2 |
| Limiting magnitude for photometry | 24.5 mag in i-band for an exposure of 2 hours |
| Limiting magnitude for spectroscopy | g=19 mag with 10 minute exposure at 0.2 nm/px dispersion |
| Calibration lamp | Hg-Ar, Ne, and continuum |
