Aryabhatta Research Institute
of observational Sciences
3.6m Devasthal Optical Telescope (DOT)
Aryabhatta Research Institute
of observational Sciences
TANSPEC is a medium-resolution spectrograph and camera having sensitivity in the wavelength range from 550 to 2540 nm.
It employs a 1024 x 1024 H1RG array with a pixel scale of 0.25 arcsec and it covers a field of view of 1 arcmin x 1 arcmin.
It offers broad-band photometry in r, i, Y, J, H, K and narrow-band H2 and BrG filters. Stellar images with FWHM of 0.5 arcsec in K-band were recorded in February 2020 in the best conditions.
The object of 18 mag in K has been successfully imaged and detected in 1-min exposure. It is possible to detect sources at J, H, K of 19.5, 18.9, 18.4 mag respectively at 10 sigma level in 10 minutes exposure.
R~23 mag source is detected in 1 hour exposure.
For spectroscopy, it employs a 2048 x 2048 H2RG array, and it can be used in cross-dispersed mode (R~2750) as well as in prism mode (R~100-350).
The slits available in these modes have widths between 0.5 to 4.0 arcsec. By our theoretical calculations,
It can be possible to take R ~ 2750 (~100-350) spectra of J=14.3 (17.3) mag source in 1 hour at 100-sigma level for stellar sources with FWHM of 1 arcsec.
TANSPEC can only be mounted on the axial-port of the telescope. Proposals should be considered for science verification in the early cycles, when the focus will be on stabilizing the TANSPEC instrument.
For high-resolution spectroscopic mode, the proposers should add about 50% of the overhead (excluding lamp / standard stars).
In the imaging mode, the overhead is about 30% (for dithering, filter change, readout, etc).
| Parameters | Value |
| Type | Imaging and spectroscopy |
| Mount position | Main axial port |
| Wavelength range | 550 - 2540 nm |
| Array size | Imaging: 1024 X 1024 pixel2, Spectroscopy: 2048 x 2048 pixel2 |
| Pixel size | 18 μm |
| Pixel scale | 0”.25 |
| Field of view | 1’ X 1’ |
| Readout noise | Imaging: 3.5 ADU, Spectroscopy: 20.7 (high-gain), 5.3 (low-gain) |
| Readout time | Imaging: 1.89s, Spectroscopy: 5.26s |
| Gain | Imaging: 4.3e-/ADU, Spectroscopy: 1.1 (high-gain), 4.5 (low-gain) |
| Minimum exposure time for imaging | 0.9 s |
| Spectroscopy modes | Cross-dispersion and prism |
| Spectral resolution | Cross-dispersion mode: 2750, Prism mode: 100-350 |
| Available filters | broadband: r, i, Y, J, H, K and narrowband: H2, BrG |
| Slits | Widths: 0”.5-4”.0 |
| Limiting magnitudes for imaging | 18 mag in K-band for an exposure of 1 min, 19.5,, 18.9, 18.4 mag in J, H, K bands, respectively, with an exposures of 10 min |
| Limiting magnitude for spectroscopy | Cross dispersion mode: J=14.3 with 1 hour exposure, Prism mode: J=17.3 with 1 hour exposure |
