2022B: Report on the WINERED observations with Magellan
Summary
We made the first light with the WIDE mode of the WINERED
at the Magellan telescope (Clay) in 2022 September.
We confirmed that the PSF upon the WINERED detector
becomes as narrow as 0.6 arcsec in FWHM depending on the seeing.
The sensitivity was as high as expected for some objects,
although it becomes almost half in the J band under some conditions
due to the differential refraction (larger in J) and the poor target tracking.
No HIRES-Y/J spectra of stars, but there are no problems expected with using the two modes.
Observations
The run was mainly for installing the WINERED and checking its performance.
Nevertheless, we managed to collect a limited amount of scientific data
beside experimental data for considering future observations.
Instrumental performance
Gnerally speaking, the WINERED co-works with the telescope well
and we can obtain high-quality spectra, as expected, although the sensitivity and
the efficiency may be lower under some conditions.
- Sensitivity:
We confirmed that the sensitivity is as high as the expectation with the ETC under good conditions.
However, there are some cases where the sensitivity becomes as low as half due to
the differential refraction and the poor tracking.
We would need more data to confirm the sensitivity better under various conditions.
On the faintest end, we have detected the signal (with S/N about a few) from an object
as faint as J=16.5 mag even though the weather condition was moderate.
- PSF:
The stellar image on the spectrograph detector looks nice, giving the FWHM as small as 0.6 arcsec within the slit in the space direction.
- Differential refraction:
With the target's altitude around 45° or lower,
the slit throughput becomes low due to the differential refraction,
i.e., the wavelength-dependent offset between
the position of the target seen by the slit viewer (red in the optical)
and the position in the J band with respect to the slit.
- Target tracking:
We found that introducing a target into the slit and tracking it was not always accurate. The sensitivity could be lower by 20-30 percent than the ideal case. We are working to improve this by modifying the algorithm and software in the next semester.
- Slit Viewer:
The SV (sensitive to 0.6—0.9 μm) gives reasonable images, allowing observers to introduce targets.
The limiting magnitude may be as deep as 19 mag (capturing signals with a ∼30 sec exposure),
but we would need significantly brighter stars (around 16 mag?, to be confirmed) to guide the tracking. We are planning to improve the SV (to have a larger dynamical range and/or to get the sensitivity to the near infrared) in the future.
Allocation
- 2022/09/12 — McWilliam (Carnegie)
- 2022/09/13 — McWilliam (Carnegie)
- 2022/09/14 — Rauch (Carnegie)
- 2022/09/15 — McWilliam (Carnegie)
- 2022/09/16 — McWilliam (Carnegie)
Daily Log
- 2022/09/12 (WIDE) — Making the alignment between the WINERED and the telescope was unsuccessful.
- 2022/09/13 (WIDE) — The alignment was only roughly done and we made some test of the operation of the WINERED attached to the telescope.
- 2022/09/14 (WIDE) — The alignment was successfully done and we took some spectroscopic data including some scientific targets. The weather condition was good.
- 2022/09/15 (WIDE) — We improved the alignment and made further tests of the operation. Together with the test of operations such as nodding and tracking, we made some scientific observations, but the sky was not very clear.
- 2022/09/16 (HIRES-Y) — Cloudy for the entire night.
Links